The Moonraker mission is a proposed ESA M-class mission to study Enceladus through multiple flybys. Its goals are to 1) assess the habitability of Enceladus' subsurface ocean by analyzing plume composition, 2) understand communication between the ocean and surface, and 3) determine Enceladus' formation conditions. It would carry advanced instruments to precisely measure species, isotopes, and physical properties in the plume and on the surface. The mission aims to characterize Enceladus' potential as an abiotic and biological oasis.
Evidence for plumes of water on Europa has previously been found using the Hubble Space Telescope using two
different observing techniques. Roth et al. found line emission from the dissociation products of water. Sparks et al.
found evidence for off-limb continuum absorption as Europa transited Jupiter. Here, we present a new transit
observation of Europa that shows a second event at the same location as a previous plume candidate from Sparks
et al., raising the possibility of a consistently active source of erupting material on Europa. This conclusion is
bolstered by comparison with a nighttime thermal image from the Galileo Photopolarimeter-Radiometer that shows
a thermal anomaly at the same location, within the uncertainties. The anomaly has the highest observed brightness
temperature on the Europa nightside. If heat flow from a subsurface liquid water reservoir causes the thermal
anomaly, its depth is ≈1.8–2 km, under simple modeling assumptions, consistent with scenarios in which a liquid
water reservoir has formed within a thick ice shell. Models that favor thin regions within the ice shell that connect
directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface
activity. Alternatively, vapor deposition surrounding an active vent could increase the thermal inertia of the surface
and cause the thermal anomaly. This candidate plume region may offer a promising location for an initial
characterization of Europa’s internal water and ice and for seeking evidence of Europa’s habitability.
Prospects for Cryovolcanic Activity on Cold Ocean PlanetsSérgio Sacani
We have estimated total internal heating rates and depths to possible subsurface oceans for 17 planets that may be
cold ocean planets, low-mass exoplanets with equilibrium surface temperatures and/or densities that are consistent
with icy surfaces and a substantial H2O content. We have also investigated the potential for tidally driven
cryovolcanism and exosphere formation on these worlds. Estimated internal heating rates from tidal and radiogenic
sources are large enough that all planets in our study may harbor subsurface oceans, and their geological activity
rates are likely to exceed the geological activity rates on Jupiter’s moon Europa. Several planets are likely to
experience enhanced volcanic activity rates that exceed that of Io. Owing to their relatively thin ice shells and high
rates of internal heating, Proxima Cen b and LHS 1140 b are the most favorable candidates for telescopic detection
of explosive, tidally driven cryovolcanism. Estimates for thin ice shells on Proxima Cen b, LHS 1140 b, Trappist1f, and several Kepler planets suggest that any H2O vented into space during explosive cryovolcanic eruptions on
these worlds could be sourced directly from their subsurface oceans. Like the icy moons in our outer solar system,
cold ocean planets may be astrobiologically significant worlds that harbor habitable environments beneath their icy
surfaces. These possibilities should be considered during analyses of observational data for small exoplanets from
current and upcoming telescopes and during planning for a future space telescope mission aimed at characterization
of potentially habitable exoplanets (e.g., Habitable Worlds Observatory).
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Two temperate Earth-mass planets orbiting the nearby star GJ 1002Sérgio Sacani
We report the discovery and characterisation of two Earth-mass planets orbiting in the habitable zone of the nearby M-dwarf GJ 1002 based on
the analysis of the radial-velocity (RV) time series from the ESPRESSO and CARMENES spectrographs. The host star is the quiet M5.5 V star
GJ 1002 (relatively faint in the optical, V ∼ 13.8 mag, but brighter in the infrared, J ∼ 8.3 mag), located at 4.84 pc from the Sun.
We analyse 139 spectroscopic observations taken between 2017 and 2021. We performed a joint analysis of the time series of the RV and full-width
half maximum (FWHM) of the cross-correlation function (CCF) to model the planetary and stellar signals present in the data, applying Gaussian
process regression to deal with the stellar activity.
We detect the signal of two planets orbiting GJ 1002. GJ 1002 b is a planet with a minimum mass mp sin i of 1.08 ± 0.13 M⊕ with an orbital period
of 10.3465 ± 0.0027 days at a distance of 0.0457 ± 0.0013 au from its parent star, receiving an estimated stellar flux of 0.67 F⊕. GJ 1002 c is a
planet with a minimum mass mp sin i of 1.36 ± 0.17 M⊕ with an orbital period of 20.202 ± 0.013 days at a distance of 0.0738 ± 0.0021 au from
its parent star, receiving an estimated stellar flux of 0.257 F⊕. We also detect the rotation signature of the star, with a period of 126 ± 15 days. We
find that there is a correlation between the temperature of certain optical elements in the spectrographs and changes in the instrumental profile that
can affect the scientific data, showing a seasonal behaviour that creates spurious signals at periods longer than ∼ 200 days.
GJ 1002 is one of the few known nearby systems with planets that could potentially host habitable environments. The closeness of the host star
to the Sun makes the angular sizes of the orbits of both planets (∼ 9.7 mas and ∼ 15.7 mas, respectively) large enough for their atmosphere to be
studied via high-contrast high-resolution spectroscopy with instruments such as the future spectrograph ANDES for the ELT or the LIFE mission.
TESS and CHEOPS discover two warm sub-Neptunes transiting the bright K-dwarf ...Sérgio Sacani
We report the discovery of two warm sub-Neptunes transiting the bright (G = 9.5 mag) K-dwarf HD 15906 (TOI 461,
TIC 4646810). This star was observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 4 and 31, revealing
two small transiting planets. The inner planet, HD 15906 b, was detected with an unambiguous period but the outer planet,
HD 15906 c, showed only two transits separated by ∼ 734 d, leading to 36 possible values of its period. We performed follow-up
observations with the CHaracterising ExOPlanet Satellite (CHEOPS) to confirm the true period of HD 15906 c and improve the
radius precision of the two planets. From TESS, CHEOPS, and additional ground-based photometry, we find that HD 15906 b has
a radius of 2.24 ± 0.08 R⊕ and a period of 10.924709 ± 0.000032 d, whilst HD 15906 c has a radius of 2.93+0.07 −0.06 R⊕ and a period
of 21.583298+0.000052
−0.000055 d. Assuming zero bond albedo and full day-night heat redistribution, the inner and outer planet have equilibrium temperatures of 668 ± 13 K and 532 ± 10 K, respectively. The HD 15906 system has become one of only six multiplanetsystems with two warm ( 700 K)sub-Neptune sized planetstransiting a brightstar (G ≤ 10 mag). It is an excellent target for detailed
characterization studies to constrain the composition of sub-Neptune planets and test theories of planet formation and evolution.
A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar f...Sérgio Sacani
The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than
the methane-rich bodies of the Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be
spherical and to have possibly undergone interior melting and differentiation. They also reside
on very different orbits, making them an ideal suite of bodies for untangling effects of size and
orbit on present day surface composition. We observed Sedna, Gonggong, and Quaoar with the
NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were
observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 μm. Quaoar was
additionally observed at 10x higher spectral resolution from 0.97 to 3.16 μm using mediumresolution gratings. Sedna’s spectrum shows a large number of absorption features due to ethane
(C2H6), as well as acetylene (C2H2), ethylene (C2H4), H2O, and possibly minor CO2.
Gonggong’s spectrum also shows several, but fewer and weaker, ethane features, along with
stronger and cleaner H2O features and CO2 complexed with other molecules. Quaoar’s prism
spectrum shows even fewer and weaker ethane features, the deepest and cleanest H2O features, a
feature at 3.2 μm possibly due to HCN, and CO2 ice. The higher-resolution medium grating
spectrum of Quaoar reveals several overtone and combination bands of ethane and methane
(CH4). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions
between 2.7 and 3.6 μm indicative of complex organic molecules. The suite of light
hydrocarbons and complex organic molecules are interpreted as the products of irradiation of
methane. The differences in apparent abundances of irradiation products among these three
similarly-sized bodies are likely due to their distinctive orbits, which lead to different timescales
of methane retention and to different charged particle irradiation environments. In all cases,
however, the continued presence of light hydrocarbons implies a resupply of methane to the
2
surface. We suggest that these three bodies have undergone internal melting and geochemical
evolution similar to the larger dwarf planets and distinct from all smaller KBOs. The feature
identification presented in this paper is the first step of analysis, and additional insight into the
relative abundances and mixing states of materials on these surfaces will come from future
spectral modeling of these data.
Detection and characterisation of icy cavities on the nucleus of comet 67P/Ch...Sérgio Sacani
We report on the detection of three icy cavities on the nucleus of comet 67P/Churyumov-Gerasimenko. They were identified on
high-resolution anaglyphs built from images acquired by the OSIRIS instrument aboard the Rosetta spacecraft on 2016 April
9-10. Visually, they appear as bright patches of typically 15 to 30 m across whose large reflectances and spectral slopes in
the visible substantiate the presence of sub-surface water ice. Using a new high-resolution photogrammetric shape model, we
determined the three-dimensional shape of these cavities whose depth ranges from 20 to 47 m. Spectral slopes were interpreted
with models combining water ice and refractory dark material and the water ice abundances in the cavities were found to amount
to a few per cent. The determination of the lifetime of the icy cavities was strongly biased by the availability of appropriate and
favourable observations, but we found evidences of values of up to two years. The icy cavities were found to be connected to jets
well documented in past studies. A thermal model allowed us to track their solar insolation over a large part of the orbit of the
comet and a transitory bright jet on 2015 July 18 was unambiguously linked to the brief illumination of the icy bottom of one of
the cavities. These cavities are likely to be the first potential subsurface access points detected on a cometary nucleus and their
lifetimes suggest that they reveal pristine sub-surface icy layers or pockets rather than recently recondensed water vapor.
AT 2022aedm and a New Class of Luminous, Fast-cooling Transients in Elliptica...Sérgio Sacani
This document reports the discovery and follow-up observations of a remarkable fast-evolving optical transient called AT 2022aedm. Key points:
- AT 2022aedm was discovered by the ATLAS survey and reached an extremely luminous peak magnitude of Mg ≈ -22 mag.
- It exhibited an unusually fast rise time of 9 days and faded by 2 magnitudes in the following 15 days.
- Most surprisingly, its host galaxy was found to be a massive elliptical galaxy with negligible star formation.
- Extensive follow-up observations including spectroscopy found it shared properties with two other similar transients in passive galaxies, suggesting a new class of "luminous fast coolers." However
Evidence for plumes of water on Europa has previously been found using the Hubble Space Telescope using two
different observing techniques. Roth et al. found line emission from the dissociation products of water. Sparks et al.
found evidence for off-limb continuum absorption as Europa transited Jupiter. Here, we present a new transit
observation of Europa that shows a second event at the same location as a previous plume candidate from Sparks
et al., raising the possibility of a consistently active source of erupting material on Europa. This conclusion is
bolstered by comparison with a nighttime thermal image from the Galileo Photopolarimeter-Radiometer that shows
a thermal anomaly at the same location, within the uncertainties. The anomaly has the highest observed brightness
temperature on the Europa nightside. If heat flow from a subsurface liquid water reservoir causes the thermal
anomaly, its depth is ≈1.8–2 km, under simple modeling assumptions, consistent with scenarios in which a liquid
water reservoir has formed within a thick ice shell. Models that favor thin regions within the ice shell that connect
directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface
activity. Alternatively, vapor deposition surrounding an active vent could increase the thermal inertia of the surface
and cause the thermal anomaly. This candidate plume region may offer a promising location for an initial
characterization of Europa’s internal water and ice and for seeking evidence of Europa’s habitability.
Prospects for Cryovolcanic Activity on Cold Ocean PlanetsSérgio Sacani
We have estimated total internal heating rates and depths to possible subsurface oceans for 17 planets that may be
cold ocean planets, low-mass exoplanets with equilibrium surface temperatures and/or densities that are consistent
with icy surfaces and a substantial H2O content. We have also investigated the potential for tidally driven
cryovolcanism and exosphere formation on these worlds. Estimated internal heating rates from tidal and radiogenic
sources are large enough that all planets in our study may harbor subsurface oceans, and their geological activity
rates are likely to exceed the geological activity rates on Jupiter’s moon Europa. Several planets are likely to
experience enhanced volcanic activity rates that exceed that of Io. Owing to their relatively thin ice shells and high
rates of internal heating, Proxima Cen b and LHS 1140 b are the most favorable candidates for telescopic detection
of explosive, tidally driven cryovolcanism. Estimates for thin ice shells on Proxima Cen b, LHS 1140 b, Trappist1f, and several Kepler planets suggest that any H2O vented into space during explosive cryovolcanic eruptions on
these worlds could be sourced directly from their subsurface oceans. Like the icy moons in our outer solar system,
cold ocean planets may be astrobiologically significant worlds that harbor habitable environments beneath their icy
surfaces. These possibilities should be considered during analyses of observational data for small exoplanets from
current and upcoming telescopes and during planning for a future space telescope mission aimed at characterization
of potentially habitable exoplanets (e.g., Habitable Worlds Observatory).
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Two temperate Earth-mass planets orbiting the nearby star GJ 1002Sérgio Sacani
We report the discovery and characterisation of two Earth-mass planets orbiting in the habitable zone of the nearby M-dwarf GJ 1002 based on
the analysis of the radial-velocity (RV) time series from the ESPRESSO and CARMENES spectrographs. The host star is the quiet M5.5 V star
GJ 1002 (relatively faint in the optical, V ∼ 13.8 mag, but brighter in the infrared, J ∼ 8.3 mag), located at 4.84 pc from the Sun.
We analyse 139 spectroscopic observations taken between 2017 and 2021. We performed a joint analysis of the time series of the RV and full-width
half maximum (FWHM) of the cross-correlation function (CCF) to model the planetary and stellar signals present in the data, applying Gaussian
process regression to deal with the stellar activity.
We detect the signal of two planets orbiting GJ 1002. GJ 1002 b is a planet with a minimum mass mp sin i of 1.08 ± 0.13 M⊕ with an orbital period
of 10.3465 ± 0.0027 days at a distance of 0.0457 ± 0.0013 au from its parent star, receiving an estimated stellar flux of 0.67 F⊕. GJ 1002 c is a
planet with a minimum mass mp sin i of 1.36 ± 0.17 M⊕ with an orbital period of 20.202 ± 0.013 days at a distance of 0.0738 ± 0.0021 au from
its parent star, receiving an estimated stellar flux of 0.257 F⊕. We also detect the rotation signature of the star, with a period of 126 ± 15 days. We
find that there is a correlation between the temperature of certain optical elements in the spectrographs and changes in the instrumental profile that
can affect the scientific data, showing a seasonal behaviour that creates spurious signals at periods longer than ∼ 200 days.
GJ 1002 is one of the few known nearby systems with planets that could potentially host habitable environments. The closeness of the host star
to the Sun makes the angular sizes of the orbits of both planets (∼ 9.7 mas and ∼ 15.7 mas, respectively) large enough for their atmosphere to be
studied via high-contrast high-resolution spectroscopy with instruments such as the future spectrograph ANDES for the ELT or the LIFE mission.
TESS and CHEOPS discover two warm sub-Neptunes transiting the bright K-dwarf ...Sérgio Sacani
We report the discovery of two warm sub-Neptunes transiting the bright (G = 9.5 mag) K-dwarf HD 15906 (TOI 461,
TIC 4646810). This star was observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 4 and 31, revealing
two small transiting planets. The inner planet, HD 15906 b, was detected with an unambiguous period but the outer planet,
HD 15906 c, showed only two transits separated by ∼ 734 d, leading to 36 possible values of its period. We performed follow-up
observations with the CHaracterising ExOPlanet Satellite (CHEOPS) to confirm the true period of HD 15906 c and improve the
radius precision of the two planets. From TESS, CHEOPS, and additional ground-based photometry, we find that HD 15906 b has
a radius of 2.24 ± 0.08 R⊕ and a period of 10.924709 ± 0.000032 d, whilst HD 15906 c has a radius of 2.93+0.07 −0.06 R⊕ and a period
of 21.583298+0.000052
−0.000055 d. Assuming zero bond albedo and full day-night heat redistribution, the inner and outer planet have equilibrium temperatures of 668 ± 13 K and 532 ± 10 K, respectively. The HD 15906 system has become one of only six multiplanetsystems with two warm ( 700 K)sub-Neptune sized planetstransiting a brightstar (G ≤ 10 mag). It is an excellent target for detailed
characterization studies to constrain the composition of sub-Neptune planets and test theories of planet formation and evolution.
A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar f...Sérgio Sacani
The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than
the methane-rich bodies of the Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be
spherical and to have possibly undergone interior melting and differentiation. They also reside
on very different orbits, making them an ideal suite of bodies for untangling effects of size and
orbit on present day surface composition. We observed Sedna, Gonggong, and Quaoar with the
NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were
observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 μm. Quaoar was
additionally observed at 10x higher spectral resolution from 0.97 to 3.16 μm using mediumresolution gratings. Sedna’s spectrum shows a large number of absorption features due to ethane
(C2H6), as well as acetylene (C2H2), ethylene (C2H4), H2O, and possibly minor CO2.
Gonggong’s spectrum also shows several, but fewer and weaker, ethane features, along with
stronger and cleaner H2O features and CO2 complexed with other molecules. Quaoar’s prism
spectrum shows even fewer and weaker ethane features, the deepest and cleanest H2O features, a
feature at 3.2 μm possibly due to HCN, and CO2 ice. The higher-resolution medium grating
spectrum of Quaoar reveals several overtone and combination bands of ethane and methane
(CH4). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions
between 2.7 and 3.6 μm indicative of complex organic molecules. The suite of light
hydrocarbons and complex organic molecules are interpreted as the products of irradiation of
methane. The differences in apparent abundances of irradiation products among these three
similarly-sized bodies are likely due to their distinctive orbits, which lead to different timescales
of methane retention and to different charged particle irradiation environments. In all cases,
however, the continued presence of light hydrocarbons implies a resupply of methane to the
2
surface. We suggest that these three bodies have undergone internal melting and geochemical
evolution similar to the larger dwarf planets and distinct from all smaller KBOs. The feature
identification presented in this paper is the first step of analysis, and additional insight into the
relative abundances and mixing states of materials on these surfaces will come from future
spectral modeling of these data.
Detection and characterisation of icy cavities on the nucleus of comet 67P/Ch...Sérgio Sacani
We report on the detection of three icy cavities on the nucleus of comet 67P/Churyumov-Gerasimenko. They were identified on
high-resolution anaglyphs built from images acquired by the OSIRIS instrument aboard the Rosetta spacecraft on 2016 April
9-10. Visually, they appear as bright patches of typically 15 to 30 m across whose large reflectances and spectral slopes in
the visible substantiate the presence of sub-surface water ice. Using a new high-resolution photogrammetric shape model, we
determined the three-dimensional shape of these cavities whose depth ranges from 20 to 47 m. Spectral slopes were interpreted
with models combining water ice and refractory dark material and the water ice abundances in the cavities were found to amount
to a few per cent. The determination of the lifetime of the icy cavities was strongly biased by the availability of appropriate and
favourable observations, but we found evidences of values of up to two years. The icy cavities were found to be connected to jets
well documented in past studies. A thermal model allowed us to track their solar insolation over a large part of the orbit of the
comet and a transitory bright jet on 2015 July 18 was unambiguously linked to the brief illumination of the icy bottom of one of
the cavities. These cavities are likely to be the first potential subsurface access points detected on a cometary nucleus and their
lifetimes suggest that they reveal pristine sub-surface icy layers or pockets rather than recently recondensed water vapor.
AT 2022aedm and a New Class of Luminous, Fast-cooling Transients in Elliptica...Sérgio Sacani
This document reports the discovery and follow-up observations of a remarkable fast-evolving optical transient called AT 2022aedm. Key points:
- AT 2022aedm was discovered by the ATLAS survey and reached an extremely luminous peak magnitude of Mg ≈ -22 mag.
- It exhibited an unusually fast rise time of 9 days and faded by 2 magnitudes in the following 15 days.
- Most surprisingly, its host galaxy was found to be a massive elliptical galaxy with negligible star formation.
- Extensive follow-up observations including spectroscopy found it shared properties with two other similar transients in passive galaxies, suggesting a new class of "luminous fast coolers." However
A habitable fluvio_lacustrine_at_gale_crater_mars1Sérgio Sacani
The Curiosity rover discovered fine-grained sedimentary rocks in Yellowknife Bay, Gale crater, Mars that are inferred to represent an ancient lake environment. Analysis found the environment would have been habitable by microorganisms, with a neutral pH, low salinity, and variable redox states of iron and sulfur. Key biogenic elements like carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorus were detected, suggesting the environment could have supported a Martian biosphere based on chemolithoautotrophy. The habitable conditions were likely present for hundreds to tens of thousands of years. These results highlight the potential for fluvial-lacustrine environments on Mars after the Noachian period to
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
This document presents the first results from the JWST XUE program, which observed 15 protoplanetary disks in the NGC 6357 star-forming region using MIRI. For the disk XUE 1, located near massive stars, the following was found:
1) Abundant water, CO, CO2, HCN, and C2H2 were detected in the inner few AU, indicating an oxygen-dominated gas-phase chemistry similar to isolated disks.
2) Small crystalline silicate dust is present at the disk surface.
3) The column densities and chemistry are surprisingly similar to isolated disks despite the extreme radiation environment, implying inner disks can retain conditions conducive to rocky planet
The document summarizes findings from the Microwave Instrument on the Rosetta Orbiter (MIRO) regarding the subsurface properties and early activity of comet 67P/Churyumov-Gerasimenko. Key points:
- MIRO detected water vapor emissions from the comet beginning in early June 2014 and measured the total water production rate, which varied from 0.3 kg/s to 1.2 kg/s between June and August.
- Water outgassing displayed periodic variations correlated with the comet's 12.4-hour rotation period and seemed to originate primarily from the comet's "neck" region.
- Subsurface temperatures measured by MIRO showed seasonal and diurnal variations, indicating radiation
The document summarizes observations of water in Jupiter's stratosphere made by the Herschel Space Observatory. Herschel/HIFI obtained a 5x5 pixel map of a water emission line, finding that water decreases from southern to northern latitudes. Herschel/PACS also obtained water maps. Infrared Telescope Facility observations of methane were used to constrain stratospheric temperatures. The latitudinal distribution of water cannot be explained by temperature variations and rules out interplanetary dust as the main water source. The observations provide evidence that Jupiter's stratospheric water originated from the 1994 Shoemaker-Levy 9 comet impacts.
Venusian Habitable Climate Scenarios: Modeling Venus Through Time and Applica...Sérgio Sacani
One popular view of Venus' climate history describes a world that has spent much of its life
with surface liquid water, plate tectonics, and a stable temperate climate. Part of the basis for this
optimistic scenario is the high deuterium to hydrogen ratio from the Pioneer Venus mission that was
interpreted to imply Venus had a shallow ocean's worth of water throughout much of its history. Another
view is that Venus had a long-lived (∼100 million years) primordial magma ocean with a CO2 and steam
atmosphere. Venus' long-lived steam atmosphere would sufficient time to dissociate most of the water
vapor, allow significant hydrogen escape, and oxidize the magma ocean. A third scenario is that Venus had
surface water and habitable conditions early in its history for a short period of time (<1 Gyr), but that a
moist/runaway greenhouse took effect because of a gradually warming Sun, leaving the planet desiccated
ever since. Using a general circulation model, we demonstrate the viability of the first scenario using the
few observational constraints available.We further speculate that large igneous provinces and the global
resurfacing hundreds of millions of years ago played key roles in ending the clement period in its history
and presenting the Venus we see today. The results have implications for what astronomers term “the
habitable zone,” and if Venus-like exoplanets exist with clement conditions akin to modern Earth, we
propose to place them in what we term the “optimistic Venus zone.”
An ESA Study For The Search For Life On MarsFaith Brown
This document proposes a hypothetical strategy to search for life on Mars using robotic missions. It discusses the following key points:
1. Mars and early Earth had similar environments that could have supported the development of life, so life may have arisen on Mars as well in a primitive prokaryotic form.
2. A robotic mission should carefully select landing sites with good exobiological potential to find chemical or morphological biosignatures. Samples would be collected and analyzed using integrated instruments on a lander and rover.
3. The goal is to obtain environmental data, look for microscopic evidence of life, analyze biogeochemistry, and identify potential niches for extant life to increase the chances of detecting past or present
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU...Sérgio Sacani
This document summarizes observations from the Hubble Space Telescope of the young hot Neptune exoplanet AU Mic b, which orbits the nearby M dwarf star AU Mic. The observations aimed to detect atmospheric escape of neutral hydrogen through absorption in the stellar Lyman-alpha emission line. Two visits were obtained, one in 2020 and one in 2021, corresponding to transits of the planet. A stellar flare was observed and removed from the first visit data. In the second visit, absorption was detected in the blue wing of the Lyman-alpha line 2.5 hours before the white light transit, indicating the presence of high-velocity neutral hydrogen escaping the planet's atmosphere and traveling toward the observer. Estimates place the column density of this material
SO and SiS Emission Tracing an Embedded Planet and Compact 12CO and 13CO Coun...Sérgio Sacani
Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation
process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat
the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms
such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas
observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify
compact SO J=88–77 and SiS J=19–18 emission coincident with the position of a ∼2 MJup planet seen
as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ≈38 au. The SiS
emission is located along an azimuthal arc and has a similar morphology as a known 12CO kinematic
excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that
the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of
compact 12CO and 13CO J=3–2 emission coincident with the planet location. Taken together, a planetdriven outflow provides the best explanation for the properties of the observed chemical asymmetries.
We also resolve a bright, azimuthally-asymmetric SO ring at ≈24 au. While most of this SO emission
originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations
driven by a misaligned inner disk or planet-disk interactions. Overall, the HD 169142 disk shows
several distinct chemical signatures related to giant planet formation and presents a powerful template
for future searches of planet-related chemical asymmetries in protoplanetary disks.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
Predictions of the_atmospheric_composition_of_gj_1132_bSérgio Sacani
GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly
characterizable small exoplanets currently known. In this paper we study the interaction of a magma
ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more
than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the
amount of O2
that can build up in the atmosphere as a result of hydrogen dissociation and loss.
We find that the magma ocean absorbs at most ∼ 10% of the O2 produced, whereas more than
90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132 b from our
simulations is a tenuous atmosphere dominated by O2
, although for very large initial water abundances
atmospheres with several thousands of bars of O2
are possible. A substantial steam envelope would
indicate either the existence of an earlier H2
envelope or low XUV flux over the system’s lifetime. A
steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Further
modeling is needed to study the evolution of CO2
or N2
-rich atmospheres on GJ 1132 b.
JWST molecular mapping and characterization of Enceladus’ water plume feeding...Sérgio Sacani
Enceladus is a prime target in the search for life in our solar system, having an active plume
likely connected to a large liquid water subsurface ocean. Using the sensitive NIRSpec
instrument onboard JWST, we searched for organic compounds and characterized the plume’s
composition and structure. The observations directly sample the fluorescence emissions of H2O
and reveal an extraordinarily extensive plume (up to 10,000 km or 40 Enceladus radii) at
cryogenic temperatures (25 K) embedded in a large bath of emission originating from Enceladus'
torus. Intriguingly, the observed outgassing rate (300 kg/s) is similar to that derived from closeup observations with Cassini 15 years ago, and the torus density is consistent with previous
spatially unresolved measurements with Herschel 13 years ago, suggesting that the vigor of gas
eruption from Enceladus has been relatively stable over decadal timescales. This level of activity
is sufficient to maintain a derived column density of 4.5×1017 m-2 for the embedding equatorial
torus, and establishes Enceladus as the prime source of water across the Saturnian system. We
performed searches for several non-water gases (CO2, CO, CH4, C2H6, CH3OH), but none were
identified in the spectra. On the surface of the trailing hemisphere, we observe strong H2O ice
features, including its crystalline form, yet we do not recover CO2, CO nor NH3 ice signatures
from these observations. As we prepare to send new spacecraft into the outer solar system, these
observations demonstrate the unique ability of JWST in providing critical support to the
exploration of distant icy bodies and cryovolcanic plumes.
Two warm Neptunes transiting HIP 9618 revealed by TESS and CheopsSérgio Sacani
This document summarizes the discovery of two warm Neptunes transiting the bright star HIP 9618, as revealed by TESS and CHEOPS observations. TESS observed two transits of one planet (HIP 9618 b), separated by an 11.8 day gap, and one transit of a second planet (HIP 9618 c). Follow-up photometry and reanalysis of the TESS data determined the true period of HIP 9618 b to be 20.77291 days. CHEOPS then performed targeted photometry to determine the true 52.56349 day period of HIP 9618 c. High-resolution spectroscopy found HIP 9618 b has a mass of 10.0 ± 3.
Hot Earth or Young Venus? A nearby transiting rocky planet mysterySérgio Sacani
Venus and Earth provide astonishingly different views of the evolution of a rocky planet, raising the question of why these two rock y worlds evolv ed so differently. The recently disco v ered transiting Super-Earth LP 890-9c (TOI-4306c, SPECULOOS-2c) is a key to the question. It circles a nearby M6V star in 8.46 d. LP890-9c receives similar flux as modern Earth, which puts it very close to the inner edge of the Habitable Zone (HZ), where models differ strongly in their prediction of how long rocky planets can hold onto their water. We model the atmosphere of a hot LP890-9c at the inner edge of the HZ, where the planet could sustain several very different environments. The resulting transmission spectra differ considerably between a hot, wet exo-Earth, a steamy planet caught in a runaway greenhouse, and an exo-Venus. Distinguishing these scenarios from the planet’s spectra will provide critical new insights into the evolution of hot terrestrial planets into exo-Venus. Our model and spectra are available online as a tool to plan observations. They show that observing LP890-9c can provide key insights into the evolution of a rocky planet at the inner edge of the HZ as well as the long-term future of Earth.
Refined parameters of the HD 22946 planetary system and the true orbital peri...Sérgio Sacani
Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period
planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared
to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star
around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital
period of the outermost planet d was unknown until now.
Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d
and to refine the orbital and planetary properties of the system, especially the radii of the planets.
Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS.
We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and
then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky
Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in
order to obtain final planetary and system parameters.
Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d
to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R⊕, 2.328 ± 0.039 R⊕, and
2.607 ± 0.060 R⊕ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ
upper limits for these respective planet masses, which are 13.71 M⊕, 9.72 M⊕, and 26.57 M⊕. We estimated that another 48 ESPRESSO
radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host
star.
Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission
spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar
confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and
internal structure.
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Dust production and_particle_acceleration_in_supernova_1987_a_revealed_with_almaSérgio Sacani
This document presents spatially resolved submillimeter observations of supernova remnant SN 1987A using the Atacama Large Millimeter/Submillimeter Array (ALMA). The observations reveal that at longer wavelengths (2.8 mm - 1.4 mm), the emission is from a torus associated with the supernova shock wave, while at shorter wavelengths (870 μm - 450 μm) the emission is dominated by the inner supernova ejecta. For the first time, the dust emission is unambiguously shown to originate from the inner ejecta rather than from the surrounding material, supporting theoretical models of significant dust production in supernovae. The observations also allow separation of synchrotron emission from shock-accelerated particles in
One tenth solar_abundances_along_the_body_of-the_streamSérgio Sacani
This document summarizes a study that analyzed spectra from four background quasars to measure the chemical abundances along the Magellanic Stream. Two key findings are:
1) The sightlines toward RBS 144 and NGC 7714 yielded metallicities of around 0.1 times the solar value, indicating a uniform low abundance along the main body of the Stream. This supports models where the Stream was stripped from the SMC around 1-2.5 billion years ago when the SMC had a metallicity of around 0.1 solar.
2) A higher metallicity of around 0.5 solar was found in the inner Stream toward Fairall 9, sampling a filament traced to the LMC. This shows the bifurc
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
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Refined parameters of the HD 22946 planetary system and the true orbital peri...Sérgio Sacani
Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period
planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared
to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star
around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital
period of the outermost planet d was unknown until now.
Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d
and to refine the orbital and planetary properties of the system, especially the radii of the planets.
Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS.
We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and
then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky
Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in
order to obtain final planetary and system parameters.
Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d
to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R⊕, 2.328 ± 0.039 R⊕, and
2.607 ± 0.060 R⊕ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ
upper limits for these respective planet masses, which are 13.71 M⊕, 9.72 M⊕, and 26.57 M⊕. We estimated that another 48 ESPRESSO
radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host
star.
Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission
spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar
confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and
internal structure.
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Dust production and_particle_acceleration_in_supernova_1987_a_revealed_with_almaSérgio Sacani
This document presents spatially resolved submillimeter observations of supernova remnant SN 1987A using the Atacama Large Millimeter/Submillimeter Array (ALMA). The observations reveal that at longer wavelengths (2.8 mm - 1.4 mm), the emission is from a torus associated with the supernova shock wave, while at shorter wavelengths (870 μm - 450 μm) the emission is dominated by the inner supernova ejecta. For the first time, the dust emission is unambiguously shown to originate from the inner ejecta rather than from the surrounding material, supporting theoretical models of significant dust production in supernovae. The observations also allow separation of synchrotron emission from shock-accelerated particles in
One tenth solar_abundances_along_the_body_of-the_streamSérgio Sacani
This document summarizes a study that analyzed spectra from four background quasars to measure the chemical abundances along the Magellanic Stream. Two key findings are:
1) The sightlines toward RBS 144 and NGC 7714 yielded metallicities of around 0.1 times the solar value, indicating a uniform low abundance along the main body of the Stream. This supports models where the Stream was stripped from the SMC around 1-2.5 billion years ago when the SMC had a metallicity of around 0.1 solar.
2) A higher metallicity of around 0.5 solar was found in the inner Stream toward Fairall 9, sampling a filament traced to the LMC. This shows the bifurc
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
Similar to Moonraker – Enceladus Multiple Flyby Mission (20)
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
CLASS 12th CHEMISTRY SOLID STATE ppt (Animated)eitps1506
Description:
Dive into the fascinating realm of solid-state physics with our meticulously crafted online PowerPoint presentation. This immersive educational resource offers a comprehensive exploration of the fundamental concepts, theories, and applications within the realm of solid-state physics.
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Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
PPT on Alternate Wetting and Drying presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
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When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
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The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
1. Draft version November 3, 2022
Typeset using L
A
TEX twocolumn style in AASTeX631
Moonraker – Enceladus Multiple Flyby Mission
O. Mousis ,1, 2
A. Bouquet,3, 1
Y. Langevin,4
N. André ,5
H. Boithias,6
G. Durry,7
F. Faye,6
P. Hartogh,8
J. Helbert ,9
L. Iess,10
S. Kempf,11
A. Masters,12
F. Postberg,13
J.-B. Renard,14
P. Vernazza,1
A. Vorburger ,15
P. Wurz ,15
D.H. Atkinson,16
S. Barabash,17
M. Berthomier,18
J. Brucato,19
M. Cable ,16
J. Carter,1
S. Cazaux,20, 21
A. Coustenis ,22
G. Danger,3, 2
V. Dehant ,23
T. Fornaro,19
P. Garnier,24
T. Gautier ,25, 22
O. Groussin,1
L.Z. Hadid ,26
J.-C. Ize,1
I. Kolmasova ,27, 28
J.-P. Lebreton,14
S. Le Maistre ,23
E. Lellouch,22
J.I. Lunine,29
K.E. Mandt,30
Z. Martins ,31
D. Mimoun ,32
Q. Nenon,24
G.M. Muñoz Caro,33
P. Rannou,7
H. Rauer,9
P. Schmitt-Kopplin,34
A. Schneeberger,1
M. Simons,16
K. Stephan,9
T. Van Hoolst,23
J. Vaverka,28
M. Wieser ,17
and L. Wörner35
1Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM, Marseille, France
2Institut universitaire de France (IUF)
3Aix-Marseille Université, CNRS, Institut Origines, PIIM, Marseille, France
4IAS, Institut d’Astrophysique Spatiale, Université Paris-Saclay, CNRS, Orsay, France
5Institut de Recherche en Astrophysique et Planétologie, 9 avenue du Colonel Roche, 31028, Toulouse Cedex 4, France
6Airbus Defence & Space
7Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR 7331, CNRS, Université de Reims,
Champagne Ardenne, Campus Sciences Exactes et Naturelles, BP 1039, 51687, Reims, France
8Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
9Institute for Planetary Research, DLR, Berlin, Germany
10Dipartimento di ingegneria meccanica e aerospaziale, Universitá La Sapienza, Roma, Italy
11LASP, University of Colorado, Boulder, CO, USA
12Imperial College London, London, UK
13Institute of Geological Sciences, Freie Universität Berlin, Germany
14LPC2E, CNRS, Université Orléans, CNES, 3A avenue de la Recherche Scientifique, 45071, Orléans Cedex 2, France
15Physics Institute, University of Bern, Bern, Switzerland
16Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr, Pasadena, CA 91109-8001, USA
17Swedish Institute of Space Physics, Kiruna, Sweden
18Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau, France
19INAF-Astrophysical Observatory of Arcetri, Florence, Italy
20Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
21Leiden Observatory, Leiden University, PO Box 9513, 2300, RA Leiden, The Netherlands
22LESIA, Paris Observatory, CNRS, PSL Université, Sorbonne Université, Université de Paris, 92190 Meudon, France
23Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium
24Institut de Recherche en Astrophysique et Planétologie, 9 avenue du Colonel Roche, 31028, Toulouse Cedex 4, France
25LATMOS-IPSL, CNRS, Sorbonne Université, UVSQ-UPSaclay, Guyancourt, France
26Laboratoire de Physique des Plasmas (LPP), CNRS, Observatoire de Paris, Sorbonne Université, Université Paris Saclay, Ecole
polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France
27Department of Space Physics, Institute of Atmospheric Physics of the Czech Academy of Sciences, 141 00 Prague, Czech Republic
28Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
29Department of Astronomy, Cornell University, Ithaca, NY, USA
30Johns Hopkins Applied Physics Laboratory, Laural, MD, USA
31Centro de Quı́mica Estrutural, Institute of Molecular Sciences and Department of Chemical Engineering,
Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
32ISAE-SUPAERO, DEOS/SSPA, Université de Toulouse, France
33Centro de Astrobiologı́a (INTA-CSIC), Ctra. de Ajalvir, km 4, E-28850 Torrejón de Ardoz, Madrid, Spain
34Max Planck Institute for Extraterrestrial Physics, MPI/MPE, Center for Astrochemical Studies, Garching, Germany
35German Aerospace Center, Institute for Quantum Technologies, Ulm, Germany
Corresponding author: Olivier Mousis
olivier.mousis@lam.fr
arXiv:2211.00721v1
[astro-ph.EP]
1
Nov
2022
2. 2 Mousis et al.
ABSTRACT
Enceladus, an icy moon of Saturn, possesses an internal water ocean and jets expelling ocean material
into space. Cassini investigations indicated that the subsurface ocean could be a habitable environment
having a complex interaction with the rocky core. Further investigation of the composition of the plume
formed by the jets is necessary to fully understand the ocean, its potential habitability, and what it
tells us about Enceladus’ origin. Moonraker has been proposed as an ESA M-class mission designed
to orbit Saturn and perform multiple flybys of Enceladus, focusing on traversals of the plume. The
proposed Moonraker mission consists of an ESA-provided platform, with strong heritage from JUICE
and Mars Sample Return, and carrying a suite of instruments dedicated to plume and surface analysis.
The nominal Moonraker mission has a duration of ∼13.5 years. It includes a 23–flyby segment with 189
days allocated for the science phase, and can be expanded with additional segments if resources allow.
The mission concept consists in investigating: i) the habitability conditions of present-day Enceladus
and its internal ocean, ii) the mechanisms at play for the communication between the internal ocean
and the surface of the South Polar Terrain, and iii) the formation conditions of the moon. Moonraker,
thanks to state-of-the-art instruments representing a significant improvement over Cassini’s payload,
would quantify the abundance of key species in the plume, isotopic ratios, and physical parameters of
the plume and the surface. Such a mission would pave the way for a possible future landed mission.
Keywords: Saturnian satellites — Enceladus — Astrobiology — Natural satellite formation — Natural
satellite surfaces — Natural satellite dynamics
1. INTRODUCTION
One of the most striking discoveries of the Cassini mis-
sion to the Saturn system is the direct observation of a
plume (Dougherty et al. 2006; Tokar et al. 2006; Waite
et al. 2006; Spahn et al. 2006; Hansen et al. 2006; Porco
et al. 2006) emanating from Enceladus, a small (252
km radius) icy moon of Saturn, with multiple lines of
evidence suggesting the plume is sourced from a subsur-
face liquid water ocean. The plume emanates from the
geologically young South Polar Terrain (SPT) (Porco
et al. 2006; Dougherty et al. 2006; Hansen et al. 2006;
Spahn et al. 2006; Tokar et al. 2006; Waite Jr et al. 2006)
through four main fissures dubbed the “Tiger Stripes”.
It consists mostly of water vapor and water ice grains,
as well as CO2, CH4, H2, NH3 and complex organics
(Waite Jr et al. 2006; Hsu et al. 2015; Waite et al. 2017;
Postberg et al. 2018; Glein & Waite 2020). The ∼100
jets from the surface (Porco et al. 2014), and a likely
more diffuse emission (Spitale et al. 2015), are responsi-
ble for the replenishment of Saturn’s diffuse E-ring and
the Enceladus water torus (Hartogh et al. 2011).
Cassini data revealed Enceladus as one of the most
promising objects for habitability in the solar system
(Hemingway & Mittal 2019; Hao et al. 2022; Cable et al.
2021). The composition of the icy grains, containing var-
ious salts (Postberg et al. 2009, 2011), demonstrates a
subsurface liquid source for the plume material i.e., an
internal sea that is in contact with a rocky core. Gravity
measurements (Hemingway & Mittal 2019) and observa-
tions of the libration (Thomas et al. 2016) of the ice shell
point to a global ocean under an icy crust of variable
thickness (thinner under the SPT, see Fig. 1), in con-
tact with a rocky core of modest density, made of porous
rock and/or aqueously altered minerals. Detection of H2
in the gas phase of the plume (Waite et al. 2017), and
of SiO2 particles in E-ring grains (Hsu et al. 2015), are
evidence of ongoing or geologically recent hydrothermal
activity on Enceladus’ seafloor, resulting from alteration
of minerals by water.
On Earth, seafloor hydrothermal vents provide chem-
ical gradients that sustain lifeforms in the absence of
sunlight. On Enceladus, the composition of the volatile
phase of the plume indicates that its subsurface ocean
features chemical disequilibria that would be usable for
metabolic reactions (Waite et al. 2017; Ray et al. 2021;
Hoehler 2022). Mass spectrometry measurements in
the plume also show the presence of various organic
molecules over a wide range of masses (e.g., tentative de-
tection of C2H6, CH3OH, C8H18; varied macromolecular
organics with mass > 200 amu, awaiting further charac-
terization) (Magee & Waite 2017; Postberg et al. 2018).
Of the six elements commonly thought to be necessary
for life (C, H, O, N, P, S), only P and S have not been
firmly detected at Enceladus, likely due to their modest
abundance and the limitations of Cassini’s instruments.
The discovery of a strong thermal anomaly on Enceladus
icy surface, and the evidence for hydrothermal chemistry
(hydrogen gas, silica nanoparticles, sodium salt rich ice
grains in the plume) along with the organics and liq-
3. Moonraker 3
uid water, suggest that habitable conditions could exist
beneath the moon’s icy crust.
The question of the age and formation scenario of
Enceladus is also not completely solved (McKinnon et al.
2018), with lines of evidence indicating it may be as re-
cent as 200 Myr (Ćuk et al. 2016; Neveu & Rhoden
2019). This has implications for the formation timeline
of the Saturnian system, the materials available in the
ocean, the extent of the rock-water interaction, and the
lifetime of the ocean – and therefore the time available
for life to emerge.
Figure 1. Main characteristics of Enceladus and
its plume as understood currently. Reproduced
from Cable et al. (2021), under CC BY license
(https://creativecommons.org/licenses/by/4.0/). Back-
ground image: PIA20013 (NASA/JPL-Caltech).
All these discoveries and the related outstanding ques-
tions have recently led the 2023–2032 US National
Academies’ Planetary Science and Astrobiology Decadal
Survey to recommend NASA either a large (Flagship) or
midsize (New Frontiers) mission whose aim would be to
accomplish multiple flybys of Enceladus1
, prior to land-
ing on its surface in the case of the Flagship mission, in
addition to a higher priority Flagship mission toward the
Uranus system. In this paper, we describe a proposal for
a Saturn orbiter aiming at accomplishing several dozens
of flybys of Enceladus’ SPT, and called the Moonraker
mission (see Fig. 2). This proposal has been submitted
in response to the European Space Agency (ESA) Call
for a medium-size mission opportunity (M–class Call)
released at the end of 2021. It has been constrained by
several limitations imposed by the M–class Call (lim-
ited budget, use of Ariane 62 (AR62), 12–year cruise
duration, limited international collaboration, and lim-
ited operation duration). The submission of a more am-
bitious version of this proposal is now envisaged to the
1 https://www.nationalacademies.org/our-work/planetary-
science-and-astrobiology-decadal-survey-2023-2032
upcoming ESA Call for a large-size mission opportunity
(L–class Call).
The paper is organized as follows. Section 2 summa-
rizes the science goals of the Moonraker mission con-
cept. The proposed mission and payload configurations
are presented in Sec. 3 and Sec. 4, respectively. The
management structure of the proposed mission is de-
tailed in Sec. 5. Section 6 is devoted to conclusions and
prospects.
Figure 2. Artist view of the Moonraker mission concept.
Note that the geometry adopted for the image does not re-
flect reality. Enceladus orbits in the ring plane. The plume
sources are at most 20◦
of the south pole (Porco et al. 2014)
and do not extend as far as 45◦
as suggested by the rendition.
2. SCIENCE GOALS
Through multiple flybys above the South Polar Ter-
rain and both in situ and remote measurements, the
Moonraker mission concept addresses three main science
goals. Table 1 presents the Science Traceability Matrix.
2.1. Science Goal 1 – Habitability conditions of
present-day Enceladus
4. 4 Mousis et al.
Liquid water is only one of the conditions for life
as we know it: metabolic energy and proper “building
blocks” also need to be available in sufficient concentra-
tions. The interface of the rocky core with the ocean
is the most likely environment to be habitable on Ence-
ladus; the composition of the ocean and therefore of the
plume reflects the rock-water interaction. The measure-
ments to be performed by Moonraker answer the follow-
ing questions:
• How much chemical energy is available in the sub-
surface? Without significant solar energy, com-
plex chemical systems or even a hypothetical bio-
sphere in Enceladus’ ocean would have to rely on
chemical energy. Cassini’s measurements already
indicated that methanogenesis is a viable reaction
to sustain a potential biosphere (Waite et al. 2017;
Hsu et al. 2015), but other yet undetected chemical
species could be used for other metabolic reactions
(Ray et al. 2021). To quantify this energy, the
Moonraker mission would be able to measure the
abundances in the plume (best proxy for the ocean
itself) of key chemical species that could be used in
metabolic reactions (e.g., CO2, H2, H2S, sulfates,
O2). The flux of charged energetic particles from
Saturn’s magnetosphere hitting Enceladus’ surface
also contributes to form oxidants (Teolis et al.
2017), that can be delivered to the reducing ocean
due to constant burial by plume deposition that
exceeds radiolytic destruction (Southworth et al.
2019; Ray et al. 2021); this delivery would help
produce redox gradients. Moonraker would per-
form in situ measurements of the charged particle
environment in the vicinity of Enceladus, allow-
ing for calculation of the amount of oxidants thus
formed on the surface.
• Are the elements necessary for life as we know it
(CHNOPS) present, and in what forms and abun-
dances? While C, H, N, and O have been identi-
fied in Enceladus’ plume, P-bearing and S-bearing
species are only tentatively detected, as phosphine
and hydrogen sulfide respectively, in the gas phase
of the plume (Magee & Waite 2017). Phosphorus
and sulfur may also be present in other chemical
forms, such as phosphates (Hao et al. 2022) and
sulfates, which would be refractory. Next genera-
tion instruments aboard Moonraker would be ca-
pable of detecting trace abundances of these key
species in the plume, whether in vapor or solid
phase.
• What is the nature and extent of the interaction
between the ocean and the rocky core? Interac-
tion between the ocean and the core not only pro-
vides chemical energy (Waite et al. 2017; Hsu et al.
2015; Bouquet et al. 2017); it can also produce a
variety of organic compounds, ionic species, and
heat to sustain the ocean over the age of Ence-
ladus (Choblet et al. 2017). It is not clear at
which stage of aqueous alteration the core cur-
rently is (Zandanel et al. 2021). Ocean-core in-
teraction is also a key part in regulating the pH
of the ocean (Glein et al. 2018; Glein & Waite
2020). Key measurements to understand the geo-
chemistry of Enceladus include Ca, Mg, sulfates,
and silica in icy grains. Organic compounds, in
both gas and solid phase, represent also a criti-
cal target since they may reflect both Enceladus’
initial inventory (leached by the ocean) or com-
pounds synthesized through hydrothermal activ-
ity. Measurements in the plume can remove ambi-
guities left by the Cassini measurements and allow
us to detect low abundance compounds of interest,
including putative biomolecules.
2.2. Science Goal 2 – Communication between the
subsurface ocean and the surface through the south
polar terrain
There are still many standing questions about the ex-
act mechanisms generating the plume, and their stabil-
ity over geological timescales (Spencer et al. 2018). The
exact form of the emission (distribution of vapor and icy
grains between the jets (Porco et al. 2014) and the more
diffuse, “curtain” source (Spitale et al. 2015)), is still
not fully determined. New observational constraints are
required to understand what regulates the plume, pos-
sibly including opening and closing of vents (Ingersoll
& Nakajima 2016; Ingersoll & Ewald 2017). Aside from
the intrinsic interest in understanding the generation of
the plume, it is a crucial piece of context to interpret
the data gathered from its composition and establish a
link with oceanic composition. A deeper understanding
of the SPT and its evolution with time is invaluable for
possible future landed missions (e.g., MacKenzie et al.
(2021)). The Moonraker mission concept addresses the
following questions related to the plume generation:
• What is the size, distribution, and shape of vents
and fractures from which the plume emanates, and
the temperature distribution? Our understanding
of the morphology and size of the vents is limited
by the capabilities of the Cassini spacecraft pay-
load. Observations have provided only upper lim-
its for vents size. Different models predict different
channel widths, with different predictions such as
vents shutting off after a few years (Ingersoll &
5. Moonraker 5
Nakajima 2016) or a near insignificant endogenic
heat emission between the fractures (Kite & Rubin
2016). The study of the morphology of the vents
and the associated heat flow (including the likely
background emission between the stripes) would
allow us to constrain plume emission models. The
variation in width of the stripes (spatial varia-
tion as well as opening/closing with time) needs
to be observed at high resolution; models predict
the evolution of these openings on the timescale of
years (Spencer et al. 2018). The total heat flow
and its distribution would allow us to quantify
the effect of condensation in the vents. Moonraker
would perform remote observations at a high spa-
tial resolution to draw a new picture of the emis-
sion zone.
• How are vapor and ice grains distributed in the
plume? How has the plume evolved since the
Cassini measurements? The distribution and ve-
locity of the gas phase and ice grains, as well as
the size distribution of the ice grains, are criti-
cal parameters that models of plume generation
must reproduce. The spatial distribution of vapor
and solid sources (and correspondence to surface
features) is another outstanding question (Spencer
et al. 2018). Moonraker would combine in situ
and remote observations across many flybys to un-
derstand the plume production mechanism and its
evolution with time.
2.3. Science Goal 3 – Origin of Enceladus in the
context of the formation of Saturn’s system
Possible formation scenarios for Enceladus include a
primordial formation along with the other satellites, late
formation from ring materials, or recent (100–200 Myr
ago) formation due to a catastrophic event in the Sat-
urnian system (McKinnon et al. 2018). Distinction be-
tween these scenarios requires quantification of various
tracers such as noble gases and their isotopic ratios, and
their comparison to known measurements in the other
satellites and objects indicative of the early solar system
(e.g., chondrites and comets). Their quantification with
Moonraker measurements would allow us to address the
following question related to Enceladus’ origin:
• Which volatile tracers are primordial, and which
are evolved? How do the tracers compare to early
solar system objects and other Saturnian system
bodies? How old is Enceladus? Noble gases abun-
dances and isotopic ratios of noble gases, carbon,
nitrogen, oxygen, and hydrogen are all tied to
the reservoir from which the building blocks of
Enceladus came. Comparison of these data with
those already measured by Cassini-Huygens in Ti-
tan (Ar, Kr, and Xe abundances, D/H in CH4,
and 14
N/15
N) would indicate if the building blocks
of the two moons originate from the same mate-
rial reservoir or if they followed distinct formation
paths. Moonraker would perform measurements
at Enceladus to remove the existing ambiguities
and detect species that were under the limits of
detection (LODs) of Cassini.
3. PROPOSED MISSION CONFIGURATION
In this Section, we first depict the proposed end-to-
end Moonraker mission profile. We then provide a de-
scription of the spacecraft design, and finally discuss the
needed technology requirements.
3.1. End-To-End Mission Profile
3.1.1. Interplanetary Trajectory
Our analysis has been performed assuming that the
launcher for M-class missions would be an AR62 rocket,
with a launch capability of ∼2650 kg for a departure at
3 km/s at the optimum declination (low-south latitude).
A launch capability of ∼2185 kg for velocities in the 3.2
km/s range should be available up to a declination of
∼23◦
(N or S). The proposed baseline mission trajectory,
considering a launch in March 2036 with a velocity of
3.23 km/s at a declination of 21.8◦
N, is then:
• EVEES trajectory: one swing-by of Venus (V),
followed by a first Earth (E) swing-by to initiate a
3-years orbit, and a second Earth swing-by setting
the spacecraft on a transfer trajectory to Saturn
(S). No Deep Space Maneuver would be required;
• Arrival at Saturn in May 2048, with a relative ve-
locity of 5 km/s and a declination of 6.7◦
.
Two back-up opportunities have been identified, with
a launch in October 2036 and March 2038, with arrival
dates at Saturn in mid-year 2048 and mid-year 2050,
respectively. The proposed baseline mission would use
the AR62 launcher.
3.1.2. Saturn Orbit Insertion and early tour phases
Satellites of Saturn orbit close to the equatorial plane,
with a large angle to its orbital plane (26.7◦
). However,
an arrival at Saturn less than 3 years after the Northern
summer solstice (November 2045) results in declinations
lower than 10◦
for the nominal and first back-up oppor-
tunities. A standard pump-down sequence 383 days long
could then be implemented:
6. 6 Mousis et al.
Table 1. Moonraker Science Traceability Matrix
ESA 2022 M-class Call Moonraker – Enceladus Flyby Mission
5
Science Goals
Science
Objectives
Measurement requirements
Instrument
Progress with regard to available
data
Physical
parameter
Observables
I.
Habitability
conditions of
present-day
Enceladus
1. Determine
the
abundances
of key species
related to
habitability
(CHNOPS,
pH and
redox state,
hydrothermal
interactions,
organic
inventory)
A. Mixing ratio
in the plume
with respect to
water
H2, CH4, CO2, NH3,
CO, N2, H2S, PH3,
4He, 40Ar, volatile
organics
INMS Sensitivity > 50000 x Cassini INMS
M/ΔM > 50 x Cassini INMS
SWI
Allows remote measurements of the
whole plume
B. Abundance in
icy grains
Refractory organics:
HMOC, amino and
fatty acids
HIFI, INMS,
SWI (some
organics such
as AA
condensed on
grains)
HIFI: M/ΔM > 100 x Cassini CDA
(distinction of inorganic ion
clusters); 3.85 km/s flyby velocity
prevents organic fragmentation
SWI allows for detection of some
organics condensed on grains
Salts (incl. Mg, Ca,
Na, K), carbonates,
sulfates, SiO2,
phosphates
C. Energetic
particles altering
the surface
Abundance and
energy of ions and
electrons
Plasma
spectrometer
M/ΔM for ions = 5 x Cassini CAPS
Time resol. =45 x Cassini CAPS
E/ΔE = 10 x Cassini CAPS
2. Key
properties of
Enceladus'
hydrosphere
A. Structure of
the interior
Gravity field Radio science
Close flybys at 3.85 km/s and <100
km altitude (at least 5 dedicated RS
flybys, vs only 3 in Cassini)
II.
Communication
between the
ocean and the
surface through
the South Polar
Terrain
3. Determine
the
mechanisms
of production
of the plume
A. Size,
distribution,
shape of vents
and fractures,
temperature
distribution
High resolution
imaging
Camera
Multiple close flybys at 3.85 km/s and
<100 km altitude
Heat flux mapping SWI
Multiple close flybys at 3.85 km/s
and <100 km altitude, pixel 4 times
smaller than Cassini CIRS, sensitivity
to T as low as 20K
Ions + charged grains
in fine structure jets
Plasma
spectrometer
M/ΔM for ions = 5 x Cassini CAPS
Time resol. =45 x Cassini CAPS
E/ΔE = 10 x Cassini CAPS
B. Relative
abundance and
spatial
distribution of
the vapor and
solid phase in
the plume,
variation over
time
Abundance + size
distribution of icy
grains
HIFI,
Nephelometer
HIFI measures flux, density, velocity
No nephelometer on Cassini
Large number of 3.85 km/s flybys
provide spatial resolution and allow
for monitoring over time of plume
variations
Plasma
spectrometer
Velocity distribution
of icy grains
HIFI,
Nephelometer
Abundance,
distribution of water
vapor
INMS,
SWI Large number of 3.85 km/s flybys
provide spatial resolution
Gas kinematics SWI
III.
Origin of
Enceladus in
the context of
the formation of
Saturn's system
4. Measure
the isotopic
and chemical
composition
of key tracers
in the plume
that are
related to the
origin of
Enceladus
A. Relative
elemental
abundances
Ar, Ne, Kr, Xe
/H2O
INMS Sensitivity > 50000 x Cassini INMS
B. Isotopic
ratios
14N/15N,12C/13C,
16O/18O
INMS, TLS
INMS M/ΔM > 50 x Cassini INMS
TLS
SWI Gives value for whole plume
D/H in H2O, CH4,
NH3
INMS, TLS,
HIFI (grains
D/H),
SWI
M/ΔM for INMS (> 50x Cassini
INMS) and HIFI (>100 x Cassini
CDA) removes ambiguity (D/H in
H2O) or enables detection (other
isotopes), INMS sensitivity (>50000
Cassini INMS) enables detection of
low-abundance species, TLS
38
Ar/36
Ar
INMS
82
Kr, 83
Kr, 86
Kr /84
Kr
129
Xe, 131
Xe /132
Xe
INMS = Ion and Neutral Mass Spectrometer. HIFI= High Ice Flux Instrument. SWI= Sub-mm Wave Instrument. TLS =
Tunable Laser System.
7. Moonraker 7
• Titan flyby before Saturn Orbit Insertion (SOI)
at an altitude of 1000 km, out of Titan’s atmo-
sphere. This flyby reduces the magnitude of the
Saturn Orbit Insertion maneuver, improving the
mass budget. However, it may not be completely
outside Titan’s atmosphere, implying some uncer-
tainty about the induced drag and trajectory per-
turbation, and a source of uncertainty for the SOI.
Post flyby adjustment for the SOI trajectory might
be needed;
• SOI at pericenter (365000 km from the body cen-
ter): ∼850 m/s for 5.25 km/s (explicit solution,
the optimum requires adjusting the pericenter dis-
tance as a function of declination);
• First orbit: 18:1 (287 days) with a large Pericenter
Raise Maneuver (PRM) (250 m/s);
• Second Titan flyby: 3.35 km/s (optimum for the
science mission);
• Pump down sequence at Titan: a series of orbits of
decreasing periods – 3, 2, 1 then 2/3 Titan periods
(15.95 days) – could be achieved with Titan flybys
at altitudes higher than 1000 km (beyond the up-
per layers of the atmosphere of Titan). The Titan
flyby following the 2/3 orbit sets the spacecraft to
an orbit with a period close to 8 days, initiating
the science phase with a first flyby of Enceladus.
3.1.3. Science phase
To perform multiple flybys over the South polar re-
gion of Enceladus, an orbital period in resonance with
its 33 hours orbital period has to be selected. On this
basis, we opted for an orbit with a 6:1 orbital period
(8.22 days). This period is slightly larger than the 1:2
resonance with Titan (7.97 days). Every two orbits, Ti-
tan moves forward by 11.2◦
, and more precisely 10.5◦
due to precession. After 30 orbits (157.5◦
forward mo-
tion), Titan begins to catch up with the alternate apoc-
enter (180◦
of phasing away), but one could still imple-
ment more than 20 Enceladus flybys with minor Titan
perturbation in between before Titan gets close to the
apocenter again (see Figure 3). A grazing encounter
scheme has been selected, resulting in the slowest pos-
sible encounter velocity (∼3.85 km/s), and minimizing
the impact of precession on the encounters and orbit
maintenance costs. Therefore, a mission segment would
be constituted by a Titan to Enceladus transfer on an
orbit with a period slightly larger than the 6:1 resonance
after the first Enceladus flyby, leading to 21 to 24 Ence-
ladus flybys. At the end of this segment, the spacecraft
could be disposed of at Titan, or a new segment could
be initiated using Titan flybys. Given the specific in-
terest of the South high latitudes, all flybys have been
set over the South polar region, with the first 2 flybys
at an altitude of 200 km (to be compared to the ∼1500
km plume height), then the next flybys at 100 km or
lower at the end of the nominal mission or during an
extended mission. The latitude could however be varied
to fit scientific requirements, e.g., to perform at least 5
dedicated radio-science flybys. The nominal Moonraker
mission would have a duration of ∼13.5 years, with 189
days allocated for the science phase, assuming a 23–flyby
segment.
Figure 3. 45 flybys of Enceladus distributed over two seg-
ments (1 segment for the nominal mission + 1 segment for
an extended mission). Mission scheme: a first segment (dark
blue, A: departure from Titan outbound; B: return to Titan
inbound) provides 23 grazing flybys of Enceladus (magenta)
over the South polar regions. For an extended mission, a
2:3 inbound-outbound orbit (black) could initiate a second
segment (light blue) with 22 flybys shifted 30◦
clockwise; C:
departure from Titan; D: return to Titan for disposal or tran-
sition to a new segment initiating a new extended mission.
Regarding end of mission, the Planetary Protection
(PP) considers Enceladus as a Category III target, im-
plying that this moon is not appropriate for crashing
the spacecraft. Only some specific landing conditions in
the case of a descent module would be compliant with
the Planetary Protection Policy (see Neveu et al. (2022)
for details). The proposed scenario would be spacecraft
destruction during entry in Titan’s upper atmosphere.
Other options to be considered would be crash on an
8. 8 Mousis et al.
intermediate-sized moon that has lower PP categoriza-
tion, or delivery to a moon-free orbit around Saturn
(strategy similar to Juno’s end of mission at Jupiter).
Destruction in Saturn’s atmosphere would be too ex-
pensive in terms of energetic cost.
3.1.4. ∆V budget for evaluating mass margins
The deterministic and stochastic mission ∆V are
found to be 1410 m/s and 118 m/s, respectively. The
corresponding breakdowns are given in Table 2.
Clean-up costs would be negligible for Enceladus fly-
bys given its very low gravity potential. With a velocity
change of up to 10 m/s, a very large guidance error of
10 km only results in a difference of ∼0.3 m/s for the
orbital velocity after the flyby. Flybys of Titan at an al-
titude of 10000 km or more would be implemented when
initiating a segment. The velocity change is larger (400
m/s) than for Enceladus, but a 10 km guidance error
also leads to a difference of ∼0.4 m/s. Therefore, only
the 6 close flybys of Titan would be considered to require
significant clean-up costs.
The total ∆V is then 1528 m/s (1604 m/s with a 5%
margin). A two-segment mission, for a total of 45 flybys
of Enceladus over a 463 days mission, could be obtained
for a deterministic ∆V cost of 150 m/s instead of 60 m/s,
if remaining propellant allows. The following section
considers only a one-segment mission (23 flybys).
3.2. Spacecraft Design
The structure of the platform would be mission-
customized, with a strong heritage from JUICE. The
design of the primary structure would be first driven by
the central cylinder housing the propellant tanks and
interfacing with the launcher, and the need to support
the large solar panels as well as the JUICE-like 2.5 m di-
ameter High Gain Antenna (HGA). This results in large
support surfaces available to accommodate the payload
instruments, the platform sensor and the other aerials,
i.e., Medium Gain and Low Gain Antennae (MGA and
LGA), thrusters’ pods and main engine. The propulsion
would be similar to that of JUICE, but with downsized
propellant tanks and a single pressurant tank, in line
with mission ∆V and orbit control needs. The building
blocks of our platform would be mostly inherited from
JUICE. These elements have been considered in support
of the mass and power budget consolidation. The main
differences with respect to JUICE to meet the program-
matic constraints of a M-class mission are:
• No dedicated NAVCAM as this functionality
would be shared with the payload camera. As
for JUICE, the processing algorithms of the NAV-
CAM images would run on the platform Command
and Data Management Unit (CDMU);
• Two Star Tracker heads instead of three on
JUICE;
• European Inertial Measurement Unit (IMU) As-
trix 1000 family class would be operational and
implemented in place of the US IMU of JUICE;
• The communication system features only the
X-band chain of JUICE. The steerable JUICE
Medium Gain Antenna would be replaced by a
smaller antenna supporting minimum communi-
cations at Saturn and a few kbps during the hot
inner cruise of the early transfer phase between
Earth and Saturn;
• Due to the lower amount of solar and battery
power to be managed, the digital conditioning sys-
tem of JUICE Power Conditioning & Distribution
Units (PCDU) would be replaced by a standard
analog Maximum Power Point Tracking (MPPT)
system. A single battery module from JUICE in-
stead of five meets the spacecraft (S/C) needs;
• A couple of Input/Output (I/O) boards would be
removed from the data management Remote In-
terface Unit, in line with the reduced number of
interfaces to manage. The embedded science mass
memory of the CDMU would be also of reduced ca-
pability, to match the downlink capability of the
communication system operated at Saturn.
Using the 3G28 or 3G30 solar cells of JUICE and con-
sidering the loss of efficiency (about 5% due to majority
carrier effect) in the colder operating environment, a
143 m2
Mars Sample Return (MSR) array (total area)
at 10 AU from the Sun delivers about 380 W (to be com-
pared with 900W delivered by the JUICE 84 m2
solar
array at 5 AU), enabling an M-class spacecraft.
Preliminary mass and power budgets are presented in
Tables 3 and 4. A payload of 50 kg conssuming 50 W
over 3 hours, i.e., 150 Wh during each Enceladus flyby,
would be allocated to the payload. System margins of
25% (mass) and 30% (power) are achieved on top of es-
timates. The energy budget would be balanced with 4
hours of communications per day considering a JUICE
based system featuring a 2.5 m diameter HGA and the
JUICE X-band telemetry chain. The amount of data
downloaded to Earth varies between 0.9 Gb and 1.3 Gb
between two Enceladus flybys separated by 8 days as a
function of Earth/Saturn distance, to be allocated be-
tween the different instruments.
9. Moonraker 9
Table 2. Breakdowns of the deterministic and stochastic mission ∆V .
Deterministic ∆V
Launch window 50 m/s
Cruise 200 m/s (440 m/s and 100 m/s for the two opportunities)
SOI and pump down 1100 m/s (to be improved after optimization)
Nominal mission 60 m/s (including disposal by collision with Titan after one segment)
Stochastic ∆V
Flyby clean-up during the interplanetary phase 40 m/s
SOI + PRM 30 m/s
Titan flybys 48 m/s (8 m/s per flyby for JUICE)
Table 3. Mass budget derived from the JUICE avionics and MSR solar generator for a 50 kg science payload to Enceladus
using A62 with 25% system margin on the platform dry mass. Italic text denotes direct heritage from JUICE.
Mass kg Heritage
Launcher capability 2185 Ariane 62 (V∞ = 3.3 km/s)
S/C max. launch mass 2125 Launcher capability – 60kg adaptor
Propellant:
- Orbit manoeuvers 850 1604 m/s (incl 5% margin), 320 s Isp
- Attitude control 25 Allocation with margin
S/C max. dry mass 1250
Payload 50 Allocation
System margin 250 25% of S/C dry mass
Platform dry mass 950 Best estimate
Structure 185 15% of S/C dry mass (best estimate)
Solar arrays 340 Mars Sample Return
Harness 50 5% of S/C dry mass
Propulsion 120 JUICE architecture with one pressurant tank and two 800 L bipropellant tanks
Thermal 40 Allocation
AOCS 70 4 × reaction wheels, 2 STR, 2 × Astrix IMU, 2 Sun sensors
Communication 60 X band system including HGA and 2 LGAs, one 2 axes MGA 200 bps at Saturn
Power 60 2 × battery modules, 1 × customized PCDU, 1 axis Solar Array Drive Assembly
DMS 25 CDMU with limited SSMM, RIU with reduced I/O capabilities
AOCS = Altitude and Orbit Control System. DMS = Data Management System
10. 10 Mousis et al.
Table 4. Energy budget of the mission achieved with the MSR solar array and 500 Wh battery range. The power system supports 3
hours of science at each flyby around Closest Approach (C/A) and 4 hours of communication per day with Earth.
Power Quiet cruise Communication
sessions
Science
0.5 hour to 1.5 hour
before and after C/A
C/A ± 30 min
Duration (h) 20.0 4.0 2.0 1.0
Solar arrays 380 380 380 0 W
Total w/ margin 353 503 380 489 W
System margin 81 116 88 113 W 30% Specified
system margin
Net total 272 387 293 377 W
Payload 0 0 50 50 W
Propulsion 5 5 5 5 W
Thermal 70 50 50 50 W
AOCS 75 75 100 180 W
Communication 35 160 35 35 W
DMS 45 50 60 60 W
Power 42 47 43 47 W 95% (30 W + reg-
ulation efficiency)
Delta % Solar
arrays
27 -123 0 -489 W
Delivered to
battery
26 0 0 0 W 95% BCR
efficiency
Needed from
battery
0 515 0 515 Wh 95% BCR
efficiency
Recharge
capacity
515 0 0 0 Wh Between com-
munication
session/after
flyby
BCR = Battery Charge Regulator.
3.3. Technology requirements
No new technology development has been identified
for the spacecraft, in line with the requirements for an
M–class mission. Tailoring to the Saturn environment
is to be performed for the solar array and the solar cells.
The absence of eclipses during the multiple orbits pre-
vents the occurrence of surface temperatures as low as
experienced on JUICE. The characterization first aims
at securing power and energy budgets.
4. PAYLOAD CONFIGURATION
The scientific requirements discussed in Sec. 1 are
addressed with a suite of scientific instruments listed
in Table 5. This list includes a Mass Spectrometer, a
Tunable Laser System, a High Ice Flux Instrument, a
Nephelometer, a Plasma Spectrometer, a Submillimeter
Wave Instrument, a Camera, and a Radioscience Experi-
ment. The total mass of the scientific payload would be
39.7 kg (with an allocation of 50 kg in the mass bud-
get). This payload has been scaled to meet the spec-
ifications of an AR62 launch as provided by ESA. In
case a more powerful AR version would be available for
launch, the payload could be revised accordingly. The
present configuration also enables additional science to
be performed at Titan during the multiple approaches
of the Moonraker spacecraft.
11. Moonraker 11
Table 5. Suite of scientific instruments.
Instrument Mass (kg)
Moonraker Ion & Neutral Mass
Spectrometer (M-INMS)
6.2
Tunable Laser System (TLS) 2
High Ice Flux Instrument (HIFI) 4
Nephelometer 1
Submillimeter Wave Instrument
(SWI)
8
Camera 12
Radioscience Experiment 2
Plasma Spectrometer 4.5
Total Mass 39.7
In the following, we provide a short description of
each instrument, with their technology readiness and
heritage.
4.1. Moonraker Ion and Neutral Mass Spectrometer
(M-INMS)
M-INMS measures the composition of the neutral gas
and of the thermal ion population at the location of the
spacecraft. In this configuration, the mass spectrometer
would be provided by the University of Bern, Switzer-
land. This group has considerable space hardware ex-
perience, and in particular built the mass spectrome-
ters RTOF and DFMS of the ROSINA experiment for
Rosetta (Scherer et al. 2006; Balsiger et al. 2007), the
NGMS instrument for Luna-Resurs (Wurz et al. 2012;
Hofer et al. 2015), and the NIM instrument of the PEP
experiment on JUICE (Föhn et al. 2021). The proposed
mass spectrometer is a time of flight (TOF) mass spec-
trometer. It thus measures a full mass spectrum at once
with a mass resolution of M/∆M up to 5000. The nom-
inal and extended mass ranges are 1–300 and 1–1000
amu. The integration time for a mass spectrum could be
adjusted between 0.1 and 300 s, to optimize the spatial
resolution of the measurements as well as the sensitiv-
ity of the mass spectrometric measurements over a very
wide altitude range along the flyby trajectory. The pro-
posed mass spectrometer is comprised of an ion-optical
system and an electronic box. The ion-optical system
would be based on the RTOF instrument and the elec-
tronics on the NIM instrument on JUICE, which serves a
very similar application (mass spectrometry during fly-
bys of the Jovian moons). All subsystems have flight
heritage, thus the combined system has a Technology
Readiness Level (TRL) of 6.
4.2. Tunable Laser System (TLS)
The instrument would be provided through a consor-
tium composed of the Universities of Reims (GSMA-
CNRS) and Aix-Marseille (LAM-CNRS). The instru-
ment would be based on near-infrared antimonide laser
diode absorption spectroscopy to provide concentration
measurements of selected molecular species. The laser
beam is propagated through the molecular gas where it
is partially absorbed, the laser wavelengths being tuned
to match accordingly with a rovibronic transition of the
targeted molecules. The gas concentration is retrieved
from the measurement of the amount of absorbed laser
energy, using an adequate molecular model (Zeninari
et al. 2006). Hence, the sensor yields in situ measure-
ments of gaseous abundances inside the plume of Ence-
ladus, with a typical relative accuracy within a few per-
cent. It would be an heritage of the former TDLAS in-
strument (Durry et al. 2010) launched within the frame-
work of the Russian Martian mission Phobos-Grunt to
provide measurements of C2H2, H2O, CO2 and their iso-
topologues (Li et al. 2009; Durry et al. 2008; Le Barbu
et al. 2006a,b) from the in situ pyrolysis of a Phobos
soil sample. Therefore, the TRL of the TLS is around
8 (Durry et al. 2010). One should also mention that
an upgraded version of the TDLAS developed and led
by IKI/Roskosmos was ready to be launched within the
framework of the Exomars-2022 Martian mission (Rodin
et al. 2020).
4.3. High Ice Flux Instrument (HIFI)
HIFI would be provided by the Laboratory for Atmo-
spheric and Space Physics at Colorado University. It
would be an impact-ionization time-of-flight mass spec-
trometer which is optimized for measuring Enceladus
plume ice grains. Plume grains strike an iridium impact
plate at flythrough velocity, yielding a cloud of neutral
and ionized species; HIFI measures the small resulting
fraction of ionized species. Complementary cation and
anion spectra allow determination of the composition of
the salt-rich and organic-rich grains. The spectrometer
has a M/∆M of ∼3000, and would be able to detect or-
ganic and salt analytes in the grains’ icy matrix at ppm
concentrations. The considered mass range extends up
to more than 2000 amu. The HIFI instrument com-
prises two subsystems: a Mass Analyzer and an Elec-
tronics Box. The Mass Analyzer (MA) uses an electric
field to extract ions created by impacting grains. The
MA comprises two identical mass spectrometers: MA1
(cations) and MA2 (anions). The Electronics Box reads
out the analog signals from the Sensor Head and con-
trols its other components. HIFI would be the latest
generation in a line of successful dust analyzer instru-
12. 12 Mousis et al.
ments: Giotto PIA at comet Halley (Kissel 1986), Star-
dust CIDA at comet Wild 2 (Kissel et al. 2004), CDA
Cassini at Saturn (Srama et al. 2004), and Europa Clip-
per SUDA (to be launched in 2024). It represents a large
performance improvement over the similar ENIJA in-
strument (Srama et al. 2015) considered in the the E2T
(Mitri et al. 2018) and ELF (Reh et al. 2016) proposals.
All HIFI subsystems are at TRL 6 and above, having
been demonstrated in relevant environments via ground
test of high-fidelity prototypes or operation in space;
remaining integration involves standard interfaces and
engineering development.
4.4. Nephelometer
The instrument, named LONSCAPE (Light Optical
Nephelometer Sizer and Counter for Aerosols for Plan-
etary Environments; Renard et al. (2020b)), would be
provided through a consortium composed of the Uni-
versities of Orleans (LPC2E-CNRS) and Aix-Marseille
(LAM-CNRS). The instrument provides the scattering
function at several angles of the particles that cross a
laser beam inside an optical chamber. By doing so,
LONSCAPE performs measurements of the concentra-
tions and the typologies of the particles for 20 size classes
in the 0.1–30 µm range. The counting is performed at
the small scattering angles, where the scattered light is
mainly dependent on the diffraction and thus not sen-
sitive to the refractive index. The typology is retrieved
from the scattering properties at the several angles, by
comparison with laboratory measurements. The team
has developed instrumentation for particles detection in
particular under stratospheric balloons (Renard et al.
2020a) and in nanosatellites (Verdier et al. 2020), with
current TRL 6-7 for space applications. Also, some
studies have been conducted for an application to the
aerosols detection in the upper atmosphere of Venus
(Baines et al. 2021).
4.5. Submillimetre Wave Instrument (SWI)
The Submillimetre Wave Instrument (SWI) would be
provided by a consortium led by the Max Planck In-
stitute for Solar System Research (MPS)2
, and corre-
sponds to a passively cooled tunable heterodyne spec-
trometer covering the frequency range of 1065 to 1275
GHz. The local oscillator chain consists of a 25 GHz
band frequency synthesizer. Its output signal is tripled
to 75 GHz where it is amplified with an E-band ampli-
fier. Three frequency doublers produce a signal of a few
mW at 600 GHz, feed to a subharmonically pumped
mixer. The spectrometer backend consists of a Chirp
2 https://www.mps.mpg.de/planetary-science/juice-swi
Transform Spectrometer with 1 GHz bandwidth and 100
kHz spectral resolution. The resolving power of the in-
strument is above 1 ×107
. The receiver is coupled to a
telescope with a 29 cm primary mirror. The spatial res-
olution of the telescope is about 1 mrad. SWI would be
based on the JUICE-SWI instrument, mounted into the
JUICE satellite in August 2021, however due to mass
constraints and different scientific objectives of Moon-
raker compared to JUICE, a number of components
would be descoped: the 600 GHz receiver, the along
and cross track actuators and the autocorrelator spec-
trometers. All components of the Moonraker SWI are
TRL 8.
4.6. Camera
The camera for Moonraker would be provided by
a partnership between the University of Aix-Marseille
(LAM-CNRS) and the Institute for Planetary Research
of DLR. DLR, LAM and their partners have many years
of experience in design of optical imaging instruments
and their key-components for planetary science mis-
sions (Mars-Express (PI), Rosetta-Lander (PI), DAWN,
Hayabusa-II, ExoMars (PANCAM-HRC) and recently
JUICE (Co-PI)). The camera would be a straightfor-
ward telescope combined with a scientific VIS/NIR
CMOS- image sensor (based on JUICE-JANUS) and
their associated electronics (Della Corte et al. 2014).
The typical angular resolution that could be achieved
is 15 µrad/pixel. Because the SPT is expected to be
in the dark of polar winter during the science phase,
the illumination due to Saturn’s glow will have to be
quantified to provide a better assessment of the cam-
era design. To do so, a wide dynamic range is required.
The key components of the camera are TRL 8. In our
spacecraft design, this camera would be also used as a
navigation camera.
4.7. Radioscience Experiment
Doppler tracking of the spacecraft during flybys
(preferably via the HGA) would provide the determi-
nation of the gravity field and the orbits of the moons
(Iess et al. 2014; Durante et al. 2019). In the Moonraker
mission concept, gravity is the only available tool to con-
strain the interior structure of the Saturnian satellites.
The precise knowledge of Enceladus’ orbit is crucial to
characterize the dissipative processes in the Saturnian
system. The Doppler data would be produced at the
ground antenna via a 2-way coherent link. The measure-
ments use the onboard Radio Communication System
(RCS), without the need for dedicated equipment. If
the RCS includes the Integrated Deep Space Transpon-
der (IDST) developed by ASI and ESA, to be flown on
13. Moonraker 13
NASA’s VERITAS mission to Venus, Ka-band tracking
becomes possible, providing a significant enhancement
of the data quality and the determination of the interior
structure. Indeed, Ka band radio links (32.5–34 GHz)
are nearly immune to plasma noise, the main limitation
to Doppler measurements in X band tracking systems
(7.2–8.4 GHz). The IDST could be a contribution of
the Italian Space Agency to Moonraker, or be provided
by ESA as the onboard transponder, a system element.
The IDST, which would be based on the digital tech-
nologies developed for BepiColombo MORE investiga-
tion, enables also range measurements accurate to 1–4
cm (Cappuccio et al. 2020), thus providing very precise
data on the orbits of the moons.
4.8. Plasma spectrometer
The instrument would be provided by a con-
sortium under the responsibility of the Univer-
sity of Toulouse (IRAP-CNRS). The formed inter-
national consortium has a solid institutional ex-
perience and outstanding mission heritage, includ-
ing BepiColombo/MEA and MSA, MAVEN/SWIA,
JUICE/JDC, and Cassini/CAPS (Young et al. 2004;
Delcourt et al. 2016; Sauvaud et al. 2010; Saito et al.
2021; Wittmann et al. 2019) to thoroughly address the
scientific objectives of the Plasma Spectrometer. The
instruments consist of an electron and negative ion spec-
trometer (1–30 keV/q) together with an ion mass spec-
trometer (1–40 keV/q, M/∆M=40 for <15 keV/q) with
shared LVPS and DPU. The current TRL for the Plasma
Spectrometer is 5 at minimum for all its elements and
would be planned to reach TRL 6 by the end of Phase
A.
5. MANAGEMENT STRUCTURE
The Moonraker mission concept is proposed as an
ESA-led mission, with a contribution to the science pay-
load by NASA. Participating in the elaboration of the
Moonraker proposal is one industrial company, Airbus
Defense and Space. The international Consortium for
the Moonraker mission concept involves the platform as
well as the science instruments and science investiga-
tions. After selection by ESA, the European industrial
partner would be responsible for developing, within the
international Consortium, the platform. The Moonraker
instrument payload is provided by instrument PI teams
from ESA’s Members states and NASA scientific com-
munities. Payload funding for ESA’s members states is
provided by National funding agencies, while the U.S.
payload contribution would be funded by NASA. The
lead-funding agency for each PI-team is either the PI
National Funding Agency for a European PI-led team
or NASA for a U.S.-led PI team.
6. CONCLUSION
The Moonraker mission concept has been submitted to
the ESA Call for a medium-size mission opportunity re-
leased in December 2021. It consists of an ESA-provided
platform, with strong heritage from JUICE and Mars
Sample Return, and carrying a suite of instruments dedi-
cated to plume and surface analysis. The nominal Moon-
raker mission concept includes a 23–flyby segment and
has a duration of ∼13.5 years, with 189 days allocated
for the science phase. It can be expanded with addi-
tional segments, if needed, to satisfy the science objec-
tives. The ESA review indicated that the needed budget
is larger than the maximum one at disposal for medium
size missions (550 millions euros), and that the mission
profile is rather tailored to match that of a large-size
missions in terms of budget (∼one billion euros) and
mission design (need of a rocket more powerful than
AR62, 12–year cruise duration, extended international
collaboration, and significant operation duration).
The submission of an extended Moonraker proposal is
currently envisaged to the next ESA Call for a large-
size mission, including science both at Enceladus and
Titan, which would fit the “Moons of the giant plan-
ets” priority defined for L-class missions in the Voyage
2050 program. The Moonraker mission concept corre-
sponds to one of the top priorities of the future New
Frontiers 6 and 7 calls proposed by the 2023–2032 US
National Academies’ Planetary Science and Astrobiol-
ogy Decadal Survey. Enceladus is also considered as
the second highest priority new Flagship mission for the
decade 2023-2032 recommended by this panel, with the
highest priority attributed to the Uranus Orbiter and
Probe (UOP).
In case Ariane 64 (AR64) could be envisaged, ad-
ditional mission capability would be considered (e.g.,
extension of the payload such as the addition of a
magnetometer, more propellant to increase the orbital
phase duration). The additional available launch mass
could be considered to piggyback an additional contribu-
tion (to explore the Saturn system) from another space
agency.
If selected, such a spacecraft would also provide im-
portant follow-up science at Titan after the Dragonfly
mission. Flybys of Titan are already a part of the initial
mission profile, although at a high altitude. The ad-
ditional fuel available could allow for closer flybys, en-
abling mass spectrometry measurements in Titan’s at-
mosphere. Such a mission concept would have to over-
come any potential contamination between the succes-
sive flybys of Titan and Enceladus. To do so, M-INMS
could contain a bake-out heater designed to heat the
ion source up to 150–300◦
C for at least 24 h. This ion
14. 14 Mousis et al.
source bake-out heater would clean the ion source from
any contaminant deposited there and originating from
the spacecraft. It would also remove any chemical her-
itage from prior measurements, such as the Titan atmo-
sphere. Such an ion source bake-out system is standard
for neutral gas mass spectrometers, as illustrated by the
ROSINA/Rosetta experiment, but also by the Neutral
Gas Mass Spectrometer (NGMS) instrument for Lunar
Resurs, and the Neutral Ion Mass Spectrometer (NIM)
on the Particle Environment Package (PEP) of JUICE.
If the ion source bake-out heater would still be consid-
ered insufficient, then a hermetically sealed instrument
could be flown, with the seal only broken at Enceladus.
In addition, the risk of contamination of the HIFI in-
strument would be almost zero given the fact that it
is more or less in a vacuum tight housing, with a tiny
aperture and a target fully isolated from the ambient at-
mosphere. The HIFI team is also currently investigating
the possibility to keep the target warm during flybys to
prevent ice grains from sticking and slowly evaporating.
A larger science payload should be considered, with
the inclusion of a radar and a magnetometer. The ad-
dition of a magnetometer would allow us to use the
reported tidal variations in plume activity to explore
Enceladus’ inductive response to the resulting time-
dependence of the background magnetic field arising
from the moon-magnetosphere interaction. This will
place a constraint on global ocean thickness and salin-
ity. This instrument would also allow for additional
science related to Saturn’s magnetosphere and Titan’s
ionosphere. An ice-penetrating radar would also allow
for further understanding of the communication of Ence-
ladus’ ocean with its surface, as well as help establishing
bathymetry maps of Titan’s lakes and seas. An addi-
tional module to be dropped at Titan, such as a small
entry probe or a minisatellite, could be considered as
well.
OM and AB acknowledge support from CNES. JIL was
supported by the JPL Distinguished Visiting Scientist
Program. ZM acknowledges funding from FEDER–
Fundo Europeu de Desenvolvimento Regional funds
through the COMPETE 2020–Operational Programme
for Competitiveness and Internationalisation (POCI),
and by Portuguese funds through FCT–Fundação
para a Ciência e Tecnologia in the framework of
the project POCI-01-0145-FEDER-029932 (PTDC/FIS-
AST/29932/2017). Centro de Quı́mica Estrutural ac-
knowledges the financial support of FCT- Fundação
para a Ciência e Tecnologia (UIDB/00100/2020 and
UIDP/00100/2020), and Institute of Molecular Sciences
acknowledges the financial support of FCT—Fundação
para a Ciência e Tecnologia (LA/P/0056/2020). Some
of this work was conducted at the Jet Propulsion Labo-
ratory, California Institute of Technology, under a con-
tract with the National Aeronautics and Space Admin-
istration (80NM0018D0004). Reference herein to any
specific commercial product, process, or service by trade
name, trademark, manufacturer, or otherwise, does not
constitute or imply its endorsement by the United States
Government or the Jet Propulsion Laboratory, Califor-
nia Institute of Technology. In Memory of Prof. Anny-
Chantal Levasseur-Regourd.
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