It has been proposed that ~3.4 billion years ago an ocean fed by enormous catastrophic floods covered
most of the Martian northern lowlands. However, a persistent problem with this hypothesis is the
lack of definitive paleoshoreline features. Here, based on geomorphic and thermal image mapping in
the circum-Chryse and northwestern Arabia Terra regions of the northern plains, in combination with
numerical analyses, we show evidence for two enormous tsunami events possibly triggered by bolide
impacts, resulting in craters ~30km in diameter and occurring perhaps a few million years apart. The
tsunamis produced widespread littoral landforms, including run-up water-ice-rich and bouldery lobes,
which extended tens to hundreds of kilometers over gently sloping plains and boundary cratered
highlands, as well as backwash channels where wave retreat occurred on highland-boundary surfaces.
The ice-rich lobes formed in association with the younger tsunami, showing that their emplacement
took place following a transition into a colder global climatic regime that occurred after the older
tsunami event. We conclude that, on early Mars, tsunamis played a major role in generating and
resurfacing coastal terrains.
-Examined features ranging from valley systems in Margaritifer Sinus to inverted topography in Aeolis/Zephyria Plana
-Studied and analyzed MOLA, THEMIS-VIS, OMEGA, MOC, CRISM, HRSC, and CTX imagery
International Refereed Journal of Engineering and Science (IRJES)irjes
The core of the vision IRJES is to disseminate new knowledge and technology for the benefit of all, ranging from academic research and professional communities to industry professionals in a range of topics in computer science and engineering. It also provides a place for high-caliber researchers, practitioners and PhD students to present ongoing research and development in these areas.
A deep groundwater origin for recurring slope lineae on MarsSérgio Sacani
The recurring slope lineae on Mars have been hypothesized to originate from snow melting, deliquescence, dry flow or shallow
groundwater. Except for the dry flow origin, these hypotheses imply the presence of surficial or near-surface volatiles, placing
the exploration and characterization of potential habitable environments within the reach of existing technology. Here we present observations from the High Resolution Imaging Science Experiment, heat-flow modelling and terrestrial analogues, which
indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers
within the cryosphere, at depths of approximately 750 m. Spatial correlation between recurring slope lineae source regions and
multi-scale fractures (such as joints and faults) in the southern mid-latitudes and in Valles Marineris suggests that recurring
slope lineae preferably emanate from tectonic and impact-related fractures. We suggest that deep groundwater occasionally
surfaces on Mars in present-day conditions.
-Examined features ranging from valley systems in Margaritifer Sinus to inverted topography in Aeolis/Zephyria Plana
-Studied and analyzed MOLA, THEMIS-VIS, OMEGA, MOC, CRISM, HRSC, and CTX imagery
International Refereed Journal of Engineering and Science (IRJES)irjes
The core of the vision IRJES is to disseminate new knowledge and technology for the benefit of all, ranging from academic research and professional communities to industry professionals in a range of topics in computer science and engineering. It also provides a place for high-caliber researchers, practitioners and PhD students to present ongoing research and development in these areas.
A deep groundwater origin for recurring slope lineae on MarsSérgio Sacani
The recurring slope lineae on Mars have been hypothesized to originate from snow melting, deliquescence, dry flow or shallow
groundwater. Except for the dry flow origin, these hypotheses imply the presence of surficial or near-surface volatiles, placing
the exploration and characterization of potential habitable environments within the reach of existing technology. Here we present observations from the High Resolution Imaging Science Experiment, heat-flow modelling and terrestrial analogues, which
indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers
within the cryosphere, at depths of approximately 750 m. Spatial correlation between recurring slope lineae source regions and
multi-scale fractures (such as joints and faults) in the southern mid-latitudes and in Valles Marineris suggests that recurring
slope lineae preferably emanate from tectonic and impact-related fractures. We suggest that deep groundwater occasionally
surfaces on Mars in present-day conditions.
First results from_the_hubble_opal_program_jupiter_in_2015Sérgio Sacani
Os cientistas usando o Telescópio Espacial Hubble da NASA/ESA produziram novos mapas de Júpiter, que mostram as contínuas mudanças que ocorrem com a famosa Grande Mancha Vermelha. As imagens também revelam uma rara estrutura em forma de onda na atmosfera do planeta que não tinha sido vista por décadas. A nova imagem é a primeira de uma série de retratos anuais dos planetas externos do Sistema Solar, que nos darão um novo olhar desses mundos remotos, e ajudarão os cientistas a estudarem como eles mudam com o passar do tempo.
Nessa nova imagem de Júpiter, uma grande quantidade de feições foi capturada incluindo ventos, nuvens e tempestades. Os cientistas por trás dessas novas imagens, as obtiveram usando a Wide Field Camera 3 do Hubble, num período de observação de mais de 10 horas e produziram assim dois mapas completos do planeta, a partir das suas observações. Esses mapas fizeram com que fosse possível determinar a velocidade dos ventos em Júpiter, com a finalidade de identificar diferentes fenômenos na sua atmosfera além de traquear as suas feições mais famosas.
As novas imagens confirmam que a grande tempestade que tem existido na superfície de nuvens de Júpiter por no mínimo 300 anos, continua a encolher, mas mesmo que desapareça, ela irá morrer lutando. A tempestade, conhecida como Grande Mancha Vermelha, é vista aqui fazendo seus movimentos em espiral no centro da imagem do planeta. Ela tem diminuído de tamanho de maneira muito rápida de ano em ano. Mas agora, a taxa de encolhimento parece ter reduzido novamente, mesmo apesar da mancha ser cerca de 240 quilômetros menor do que era em 2014.
Recent north magnetic pole acceleration towards Siberia caused by flux lobe e...Sérgio Sacani
The wandering of Earth’s north magnetic pole, the location where the magnetic field points vertically downwards, has long been
a topic of scientific fascination. Since the first in situ measurements in 1831 of its location in the Canadian arctic, the pole has
drifted inexorably towards Siberia, accelerating between 1990 and 2005 from its historic speed of 0–15 km yr−1
to its present
speed of 50–60 km yr−1
. In late October 2017 the north magnetic pole crossed the international date line, passing within 390 km
of the geographic pole, and is now moving southwards. Here we show that over the last two decades the position of the north
magnetic pole has been largely determined by two large-scale lobes of negative magnetic flux on the core–mantle boundary
under Canada and Siberia. Localized modelling shows that elongation of the Canadian lobe, probably caused by an alteration
in the pattern of core flow between 1970 and 1999, substantially weakened its signature on Earth’s surface, causing the pole
to accelerate towards Siberia. A range of simple models that capture this process indicate that over the next decade the north
magnetic pole will continue on its current trajectory, travelling a further 390–660 km towards Siberia.
A contribution to the analysis of urban erosion (Democratic Republic of Congo) ExternalEvents
Mr A. Emery Murhula, Cabinet d’expertise environnemental et social (CEE), Democratic Republic of the Congo. Global Symposium on Soil Erosion (GSER19), 15 - 17 May 2019 at FAO HQ.
Detection of intact lava tubes at Marius Hills on the Moon by SELENE (Kaguya)...Sérgio Sacani
Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon’s composition and potentially serve as secure shelters for humans and instruments. We investigated the SELENE Lunar Radar Sounder (LRS) data at locations close to the Marius Hills Hole (MHH), a skylight potentially leading to an intact lava tube, and found a distinctive echo pattern exhibiting a precipitous decrease in echo power, subsequently followed by a large second echo peak that may be evidence for the existence of a lava tube. The search area was further expanded to 13.00–15.005°N, 301.85–304.01°E around the MHH and similar LRS echo patterns were observed at several locations. Most of the locations are in regions of underground mass deficit suggested by GRAIL gravity data analysis. Some of the observed echo patterns are along rille A, where the MHH was discovered, or on the southwest underground extension of the rille.
3D Facies Modelling project using Petrel software. Msc Geology and Geophysics
Abstract
The Montserrat and Sant Llorenç del Munt fan-delta complexes were developed during the Eocene in the Ebro basin. The depositional stratigraphic record of these fan deltas has been described as a made up by a several transgressive and regressive composite sequences each made up by several fundamental sequences. Each sequence set is in turn composed by five main facies belts: proximal alluvial fan, distal alluvial fan, delta front, carbonates platforms and prodelta.
Using outcrop data from three composite sequences (Sant Vicenç, Vilomara and Manresa), a 3D facies model was built. The key sequential traces of the studied area georeferenced and digitalized on to photorealistic terrain models, were the hard data used as input to reconstruct the main surfaces, which are separating transgressive and regressive stacking patterns. Regarding the facies modelling has been achieved using a geostatistical algorithm in order to define the stacking trend and the interfingerings of adjacent facies belts, and five paleogeographyc maps to reproduce the paleogeometry of the facies belts within each system tract.
The final model has been checked, using a real cross section, and analysed in order to obtain information about the Delta Front facies which are the ones susceptible to be analogous of a reservoir. Attending to the results including eight probability maps of occurrence, the transgressive sequence set of Vilomara is the greatest accumulation of these facies explained by its agradational component.
A suppression of differential rotation in Jupiter’s deep interiorSérgio Sacani
Jupiter’s atmosphere is rotating differentially, with zones and
belts rotating at speeds that differ by up to 100 metres per
second. Whether this is also true of the gas giant’s interior has
been unknown1,2
, limiting our ability to probe the structure and
composition of the planet3,4
. The discovery by the Juno spacecraft
that Jupiter’s gravity field is north–south asymmetric5
and the
determination of its non-zero odd gravitational harmonics J3, J5, J7
and J9 demonstrates that the observed zonal cloud flow must persist
to a depth of about 3,000 kilometres from the cloud tops6
. Here we
report an analysis of Jupiter’s even gravitational harmonics J4, J6,
J8 and J10 as observed by Juno5
and compared to the predictions
of interior models. We find that the deep interior of the planet
rotates nearly as a rigid body, with differential rotation decreasing
by at least an order of magnitude compared to the atmosphere.
Moreover, we find that the atmospheric zonal flow extends to more
than 2,000 kilometres and to less than 3,500 kilometres, making
it fully consistent with the constraints obtained independently
from the odd gravitational harmonics. This depth corresponds
to the point at which the electric conductivity becomes large and
magnetic drag should suppress differential rotation7
. Given that
electric conductivity is dependent on planetary mass, we expect the
outer, differentially rotating region to be at least three times deeper
in Saturn and to be shallower in massive giant planets and brown
dwarfs.
Measurement of Jupiter’s asymmetric gravity fieldSérgio Sacani
The gravity harmonics of a fluid, rotating planet can be decomposed
into static components arising from solid-body rotation and dynamic
components arising from flows. In the absence of internal dynamics,
the gravity field is axially and hemispherically symmetric and is
dominated by even zonal gravity harmonics J2n that are approximately
proportional to qn, where q is the ratio between centrifugal
acceleration and gravity at the planet’s equator1
. Any asymmetry in the
gravity field is attributed to differential rotation and deep atmospheric
flows. The odd harmonics, J3, J5, J7, J9 and higher, are a measure of the
depth of the winds in the different zones of the atmosphere2,3
. Here
we report measurements of Jupiter’s gravity harmonics (both even
and odd) through precise Doppler tracking of the Juno spacecraft
in its polar orbit around Jupiter. We find a north–south asymmetry,
which is a signature of atmospheric and interior flows. Analysis of
the harmonics, described in two accompanying papers4,5
, provides
the vertical profile of the winds and precise constraints for the depth
of Jupiter’s dynamical atmosphere.
Clusters of cyclones encircling Jupiter’s polesSérgio Sacani
The familiar axisymmetric zones and belts that characterize
Jupiter’s weather system at lower latitudes give way to pervasive
cyclonic activity at higher latitudes1
. Two-dimensional turbulence
in combination with the Coriolis β-effect (that is, the large
meridionally varying Coriolis force on the giant planets of the Solar
System) produces alternating zonal flows2
. The zonal flows weaken
with rising latitude so that a transition between equatorial jets and
polar turbulence on Jupiter can occur3,4
. Simulations with shallowwater
models of giant planets support this transition by producing
both alternating flows near the equator and circumpolar cyclones
near the poles5–9. Jovian polar regions are not visible from Earth
owing to Jupiter’s low axial tilt, and were poorly characterized by
previous missions because the trajectories of these missions did
not venture far from Jupiter’s equatorial plane. Here we report
that visible and infrared images obtained from above each pole
by the Juno spacecraft during its first five orbits reveal persistent
polygonal patterns of large cyclones. In the north, eight circumpolar
cyclones are observed about a single polar cyclone; in the south, one
polar cyclone is encircled by five circumpolar cyclones. Cyclonic
circulation is established via time-lapse imagery obtained over
intervals ranging from 20 minutes to 4 hours. Although migration of
cyclones towards the pole might be expected as a consequence of the
Coriolis β-effect, by which cyclonic vortices naturally drift towards
the rotational pole, the configuration of the cyclones is without
precedent on other planets (including Saturn’s polar hexagonal
features). The manner in which the cyclones persist without merging
and the process by which they evolve to their current configuration
are unknown.
Solar system exploration with space resources - Aiaa asm 2014_bp_9 final paperBryan Palaszewski
Solar System Exploration Augmented by
Lunar and Outer Planet Resource Utilization:
Historical Perspectives and Future Possibilities
Bryan Palaszewski 1
NASA John H. Glenn Research Center
Lewis Field
Cleveland, OH 44135
(216) 977-7493 Voice
(216) 433-5802 FAX
bryan.a.palaszewski@nasa.gov
Fuels and Space Propellants Web Site:
http://www.grc.nasa.gov/WWW/Fuels-And-Space-Propellants/foctopsb.htm
Establishing a lunar presence and creating an industrial capability on the Moon may lead to important new discoveries for all of human kind. Historical studies of lunar exploration, in-situ resource utilization (ISRU) and industrialization all point to the vast resources on the Moon and its links to future human and robotic exploration. In the historical work, a broad range of technological innovations are described and analyzed. These studies depict program planning for future human missions throughout the solar system, lunar launched nuclear rockets, and future human settlements on the Moon, respectively. Updated analyses based on the visions presented are presented. While advanced propulsion systems were proposed in these historical studies, further investigation of nuclear options using high power nuclear thermal propulsion, nuclear surface power, as well as advanced chemical propulsion can significantly enhance these scenarios.
Robotic and human outer planet exploration options are described in many detailed and extensive studies. Nuclear propulsion options for fast trips to the outer planets are discussed. To refuel such vehicles, atmospheric mining in the outer solar system has also been investigated as a means of fuel production for high energy propulsion and power. Fusion fuels such as Helium 3 (3He) and hydrogen can be wrested from the atmospheres of Uranus and Neptune and either returned to Earth or used in-situ for energy production. Helium 3 and hydrogen (deuterium, etc.) were the primary gases of interest with hydrogen being the primary propellant for nuclear thermal solid core and gas core rocket-based atmospheric flight. A series of analyses have investigated resource capturing aspects of atmospheric mining in the outer solar system. These analyses included the gas capturing rate, storage options, and different methods of direct use of the captured gases. While capturing 3He, large amounts of hydrogen and 4He are produced. With these two additional gases, the potential for fueling small and large fleets of additional exploration and exploitation vehicles exists.
Jupiter’s atmospheric jet streams extend thousands of kilometres deepSérgio Sacani
The depth to which Jupiter’s observed east–west jet streams extend
has been a long-standing question1,2
. Resolving this puzzle has
been a primary goal for the Juno spacecraft3,4
, which has been in
orbit around the gas giant since July 2016. Juno’s gravitational
measurements have revealed that Jupiter’s gravitational field
is north–south asymmetric5
, which is a signature of the planet’s
atmospheric and interior flows6
. Here we report that the measured
odd gravitational harmonics J3, J5, J7 and J9 indicate that the
observed jet streams, as they appear at the cloud level, extend
down to depths of thousands of kilometres beneath the cloud level,
probably to the region of magnetic dissipation at a depth of about
3,000 kilometres7,8
. By inverting the measured gravity values into a
wind field9
, we calculate the most likely vertical profile of the deep
atmospheric and interior flow, and the latitudinal dependence of its
depth. Furthermore, the even gravity harmonics J8 and J10 resulting
from this flow profile also match the measurements, when taking
into account the contribution of the interior structure10. These
results indicate that the mass of the dynamical atmosphere is about
one per cent of Jupiter’s total mass
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
First results from_the_hubble_opal_program_jupiter_in_2015Sérgio Sacani
Os cientistas usando o Telescópio Espacial Hubble da NASA/ESA produziram novos mapas de Júpiter, que mostram as contínuas mudanças que ocorrem com a famosa Grande Mancha Vermelha. As imagens também revelam uma rara estrutura em forma de onda na atmosfera do planeta que não tinha sido vista por décadas. A nova imagem é a primeira de uma série de retratos anuais dos planetas externos do Sistema Solar, que nos darão um novo olhar desses mundos remotos, e ajudarão os cientistas a estudarem como eles mudam com o passar do tempo.
Nessa nova imagem de Júpiter, uma grande quantidade de feições foi capturada incluindo ventos, nuvens e tempestades. Os cientistas por trás dessas novas imagens, as obtiveram usando a Wide Field Camera 3 do Hubble, num período de observação de mais de 10 horas e produziram assim dois mapas completos do planeta, a partir das suas observações. Esses mapas fizeram com que fosse possível determinar a velocidade dos ventos em Júpiter, com a finalidade de identificar diferentes fenômenos na sua atmosfera além de traquear as suas feições mais famosas.
As novas imagens confirmam que a grande tempestade que tem existido na superfície de nuvens de Júpiter por no mínimo 300 anos, continua a encolher, mas mesmo que desapareça, ela irá morrer lutando. A tempestade, conhecida como Grande Mancha Vermelha, é vista aqui fazendo seus movimentos em espiral no centro da imagem do planeta. Ela tem diminuído de tamanho de maneira muito rápida de ano em ano. Mas agora, a taxa de encolhimento parece ter reduzido novamente, mesmo apesar da mancha ser cerca de 240 quilômetros menor do que era em 2014.
Recent north magnetic pole acceleration towards Siberia caused by flux lobe e...Sérgio Sacani
The wandering of Earth’s north magnetic pole, the location where the magnetic field points vertically downwards, has long been
a topic of scientific fascination. Since the first in situ measurements in 1831 of its location in the Canadian arctic, the pole has
drifted inexorably towards Siberia, accelerating between 1990 and 2005 from its historic speed of 0–15 km yr−1
to its present
speed of 50–60 km yr−1
. In late October 2017 the north magnetic pole crossed the international date line, passing within 390 km
of the geographic pole, and is now moving southwards. Here we show that over the last two decades the position of the north
magnetic pole has been largely determined by two large-scale lobes of negative magnetic flux on the core–mantle boundary
under Canada and Siberia. Localized modelling shows that elongation of the Canadian lobe, probably caused by an alteration
in the pattern of core flow between 1970 and 1999, substantially weakened its signature on Earth’s surface, causing the pole
to accelerate towards Siberia. A range of simple models that capture this process indicate that over the next decade the north
magnetic pole will continue on its current trajectory, travelling a further 390–660 km towards Siberia.
A contribution to the analysis of urban erosion (Democratic Republic of Congo) ExternalEvents
Mr A. Emery Murhula, Cabinet d’expertise environnemental et social (CEE), Democratic Republic of the Congo. Global Symposium on Soil Erosion (GSER19), 15 - 17 May 2019 at FAO HQ.
Detection of intact lava tubes at Marius Hills on the Moon by SELENE (Kaguya)...Sérgio Sacani
Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon’s composition and potentially serve as secure shelters for humans and instruments. We investigated the SELENE Lunar Radar Sounder (LRS) data at locations close to the Marius Hills Hole (MHH), a skylight potentially leading to an intact lava tube, and found a distinctive echo pattern exhibiting a precipitous decrease in echo power, subsequently followed by a large second echo peak that may be evidence for the existence of a lava tube. The search area was further expanded to 13.00–15.005°N, 301.85–304.01°E around the MHH and similar LRS echo patterns were observed at several locations. Most of the locations are in regions of underground mass deficit suggested by GRAIL gravity data analysis. Some of the observed echo patterns are along rille A, where the MHH was discovered, or on the southwest underground extension of the rille.
3D Facies Modelling project using Petrel software. Msc Geology and Geophysics
Abstract
The Montserrat and Sant Llorenç del Munt fan-delta complexes were developed during the Eocene in the Ebro basin. The depositional stratigraphic record of these fan deltas has been described as a made up by a several transgressive and regressive composite sequences each made up by several fundamental sequences. Each sequence set is in turn composed by five main facies belts: proximal alluvial fan, distal alluvial fan, delta front, carbonates platforms and prodelta.
Using outcrop data from three composite sequences (Sant Vicenç, Vilomara and Manresa), a 3D facies model was built. The key sequential traces of the studied area georeferenced and digitalized on to photorealistic terrain models, were the hard data used as input to reconstruct the main surfaces, which are separating transgressive and regressive stacking patterns. Regarding the facies modelling has been achieved using a geostatistical algorithm in order to define the stacking trend and the interfingerings of adjacent facies belts, and five paleogeographyc maps to reproduce the paleogeometry of the facies belts within each system tract.
The final model has been checked, using a real cross section, and analysed in order to obtain information about the Delta Front facies which are the ones susceptible to be analogous of a reservoir. Attending to the results including eight probability maps of occurrence, the transgressive sequence set of Vilomara is the greatest accumulation of these facies explained by its agradational component.
A suppression of differential rotation in Jupiter’s deep interiorSérgio Sacani
Jupiter’s atmosphere is rotating differentially, with zones and
belts rotating at speeds that differ by up to 100 metres per
second. Whether this is also true of the gas giant’s interior has
been unknown1,2
, limiting our ability to probe the structure and
composition of the planet3,4
. The discovery by the Juno spacecraft
that Jupiter’s gravity field is north–south asymmetric5
and the
determination of its non-zero odd gravitational harmonics J3, J5, J7
and J9 demonstrates that the observed zonal cloud flow must persist
to a depth of about 3,000 kilometres from the cloud tops6
. Here we
report an analysis of Jupiter’s even gravitational harmonics J4, J6,
J8 and J10 as observed by Juno5
and compared to the predictions
of interior models. We find that the deep interior of the planet
rotates nearly as a rigid body, with differential rotation decreasing
by at least an order of magnitude compared to the atmosphere.
Moreover, we find that the atmospheric zonal flow extends to more
than 2,000 kilometres and to less than 3,500 kilometres, making
it fully consistent with the constraints obtained independently
from the odd gravitational harmonics. This depth corresponds
to the point at which the electric conductivity becomes large and
magnetic drag should suppress differential rotation7
. Given that
electric conductivity is dependent on planetary mass, we expect the
outer, differentially rotating region to be at least three times deeper
in Saturn and to be shallower in massive giant planets and brown
dwarfs.
Measurement of Jupiter’s asymmetric gravity fieldSérgio Sacani
The gravity harmonics of a fluid, rotating planet can be decomposed
into static components arising from solid-body rotation and dynamic
components arising from flows. In the absence of internal dynamics,
the gravity field is axially and hemispherically symmetric and is
dominated by even zonal gravity harmonics J2n that are approximately
proportional to qn, where q is the ratio between centrifugal
acceleration and gravity at the planet’s equator1
. Any asymmetry in the
gravity field is attributed to differential rotation and deep atmospheric
flows. The odd harmonics, J3, J5, J7, J9 and higher, are a measure of the
depth of the winds in the different zones of the atmosphere2,3
. Here
we report measurements of Jupiter’s gravity harmonics (both even
and odd) through precise Doppler tracking of the Juno spacecraft
in its polar orbit around Jupiter. We find a north–south asymmetry,
which is a signature of atmospheric and interior flows. Analysis of
the harmonics, described in two accompanying papers4,5
, provides
the vertical profile of the winds and precise constraints for the depth
of Jupiter’s dynamical atmosphere.
Clusters of cyclones encircling Jupiter’s polesSérgio Sacani
The familiar axisymmetric zones and belts that characterize
Jupiter’s weather system at lower latitudes give way to pervasive
cyclonic activity at higher latitudes1
. Two-dimensional turbulence
in combination with the Coriolis β-effect (that is, the large
meridionally varying Coriolis force on the giant planets of the Solar
System) produces alternating zonal flows2
. The zonal flows weaken
with rising latitude so that a transition between equatorial jets and
polar turbulence on Jupiter can occur3,4
. Simulations with shallowwater
models of giant planets support this transition by producing
both alternating flows near the equator and circumpolar cyclones
near the poles5–9. Jovian polar regions are not visible from Earth
owing to Jupiter’s low axial tilt, and were poorly characterized by
previous missions because the trajectories of these missions did
not venture far from Jupiter’s equatorial plane. Here we report
that visible and infrared images obtained from above each pole
by the Juno spacecraft during its first five orbits reveal persistent
polygonal patterns of large cyclones. In the north, eight circumpolar
cyclones are observed about a single polar cyclone; in the south, one
polar cyclone is encircled by five circumpolar cyclones. Cyclonic
circulation is established via time-lapse imagery obtained over
intervals ranging from 20 minutes to 4 hours. Although migration of
cyclones towards the pole might be expected as a consequence of the
Coriolis β-effect, by which cyclonic vortices naturally drift towards
the rotational pole, the configuration of the cyclones is without
precedent on other planets (including Saturn’s polar hexagonal
features). The manner in which the cyclones persist without merging
and the process by which they evolve to their current configuration
are unknown.
Solar system exploration with space resources - Aiaa asm 2014_bp_9 final paperBryan Palaszewski
Solar System Exploration Augmented by
Lunar and Outer Planet Resource Utilization:
Historical Perspectives and Future Possibilities
Bryan Palaszewski 1
NASA John H. Glenn Research Center
Lewis Field
Cleveland, OH 44135
(216) 977-7493 Voice
(216) 433-5802 FAX
bryan.a.palaszewski@nasa.gov
Fuels and Space Propellants Web Site:
http://www.grc.nasa.gov/WWW/Fuels-And-Space-Propellants/foctopsb.htm
Establishing a lunar presence and creating an industrial capability on the Moon may lead to important new discoveries for all of human kind. Historical studies of lunar exploration, in-situ resource utilization (ISRU) and industrialization all point to the vast resources on the Moon and its links to future human and robotic exploration. In the historical work, a broad range of technological innovations are described and analyzed. These studies depict program planning for future human missions throughout the solar system, lunar launched nuclear rockets, and future human settlements on the Moon, respectively. Updated analyses based on the visions presented are presented. While advanced propulsion systems were proposed in these historical studies, further investigation of nuclear options using high power nuclear thermal propulsion, nuclear surface power, as well as advanced chemical propulsion can significantly enhance these scenarios.
Robotic and human outer planet exploration options are described in many detailed and extensive studies. Nuclear propulsion options for fast trips to the outer planets are discussed. To refuel such vehicles, atmospheric mining in the outer solar system has also been investigated as a means of fuel production for high energy propulsion and power. Fusion fuels such as Helium 3 (3He) and hydrogen can be wrested from the atmospheres of Uranus and Neptune and either returned to Earth or used in-situ for energy production. Helium 3 and hydrogen (deuterium, etc.) were the primary gases of interest with hydrogen being the primary propellant for nuclear thermal solid core and gas core rocket-based atmospheric flight. A series of analyses have investigated resource capturing aspects of atmospheric mining in the outer solar system. These analyses included the gas capturing rate, storage options, and different methods of direct use of the captured gases. While capturing 3He, large amounts of hydrogen and 4He are produced. With these two additional gases, the potential for fueling small and large fleets of additional exploration and exploitation vehicles exists.
Jupiter’s atmospheric jet streams extend thousands of kilometres deepSérgio Sacani
The depth to which Jupiter’s observed east–west jet streams extend
has been a long-standing question1,2
. Resolving this puzzle has
been a primary goal for the Juno spacecraft3,4
, which has been in
orbit around the gas giant since July 2016. Juno’s gravitational
measurements have revealed that Jupiter’s gravitational field
is north–south asymmetric5
, which is a signature of the planet’s
atmospheric and interior flows6
. Here we report that the measured
odd gravitational harmonics J3, J5, J7 and J9 indicate that the
observed jet streams, as they appear at the cloud level, extend
down to depths of thousands of kilometres beneath the cloud level,
probably to the region of magnetic dissipation at a depth of about
3,000 kilometres7,8
. By inverting the measured gravity values into a
wind field9
, we calculate the most likely vertical profile of the deep
atmospheric and interior flow, and the latitudinal dependence of its
depth. Furthermore, the even gravity harmonics J8 and J10 resulting
from this flow profile also match the measurements, when taking
into account the contribution of the interior structure10. These
results indicate that the mass of the dynamical atmosphere is about
one per cent of Jupiter’s total mass
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
Detection of lyman_alpha_emission_from_a_triply_imaged_z_6_85_galaxy_behind_m...Sérgio Sacani
We report the detection of Ly emission at 9538A
in the Keck/DEIMOS and HST WFC3
G102 grism data from a triply-imaged galaxy at z = 6:846 0:001 behind galaxy cluster MACS
J2129.4 0741. Combining the emission line wavelength with broadband photometry, line ratio upper
limits, and lens modeling, we rule out the scenario that this emission line is [O II] at z = 1:57. After
accounting for magnication, we calculate the weighted average of the intrinsic Ly luminosity to be
1:31042 erg s 1 and Ly equivalent width to be 7415A. Its intrinsic UV absolute magnitude at
1600A
is 18:60:2 mag and stellar mass (1:50:3)107 M, making it one of the faintest (intrinsic
LUV 0:14 L
UV) galaxies with Ly detection at z 7 to date. Its stellar mass is in the typical range
for the galaxies thought to dominate the reionization photon budget at z & 7; the inferred Ly escape
fraction is high (& 10%), which could be common for sub-L z & 7 galaxies with Ly emission. This
galaxy oers a glimpse of the galaxy population that is thought to drive reionization, and it shows
that gravitational lensing is an important avenue to probe the sub-L galaxy population.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
First identification of_direct_collapse_black_holes_candidates_in_the_early_u...Sérgio Sacani
The first black hole seeds, formed when the Universe was younger than ⇠ 500Myr, are recognized
to play an important role for the growth of early (z ⇠ 7) super-massive black holes.
While progresses have been made in understanding their formation and growth, their observational
signatures remain largely unexplored. As a result, no detection of such sources has been
confirmed so far. Supported by numerical simulations, we present a novel photometric method
to identify black hole seed candidates in deep multi-wavelength surveys.We predict that these
highly-obscured sources are characterized by a steep spectrum in the infrared (1.6−4.5μm),
i.e. by very red colors. The method selects the only 2 objects with a robust X-ray detection
found in the CANDELS/GOODS-S survey with a photometric redshift z & 6. Fitting their
infrared spectra only with a stellar component would require unrealistic star formation rates
(& 2000M# yr−1). To date, the selected objects represent the most promising black hole seed
candidates, possibly formed via the direct collapse black hole scenario, with predicted mass
> 105M#. While this result is based on the best photometric observations of high-z sources
available to date, additional progress is expected from spectroscopic and deeper X-ray data.
Upcoming observatories, like the JWST, will greatly expand the scope of this work.
A 17 billion_solar_mass_black_hole_in_a_group_galaxy_with_a_difuse_coreSérgio Sacani
Quasars are associated with and powered by the accretion of
material onto massive black holes; the detection of highly luminous
quasars with redshifts greater than z = 6 suggests that black holes of
up to ten billion solar masses already existed 13 billion years ago1.
Two possible present-day ‘dormant’ descendants of this population
of ‘active’ black holes have been found2 in the galaxies NGC 3842
and NGC 4889 at the centres of the Leo and Coma galaxy clusters,
which together form the central region of the Great Wall3—the
largest local structure of galaxies. The most luminous quasars,
however, are not confined to such high-density regions of the
early Universe4,5; yet dormant black holes of this high mass have
not yet been found outside of modern-day rich clusters. Here we
report observations of the stellar velocity distribution in the galaxy
NGC 1600—a relatively isolated elliptical galaxy near the centre
of a galaxy group at a distance of 64 megaparsecs from Earth. We
use orbit superposition models to determine that the black hole at
the centre of NGC 1600 has a mass of 17 billion solar masses. The
spatial distribution of stars near the centre of NGC 1600 is rather
diffuse. We find that the region of depleted stellar density in the
cores of massive elliptical galaxies extends over the same radius as
the gravitational sphere of influence of the central black holes, and
interpret this as the dynamical imprint of the black holes.
We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part
of the Survey of H I in Extremely Low-Mass Dwarfs (SHIELD) project, which is a multi-wavelength
study of galaxies with H I masses in the range of 106-107:2 M discovered by the ALFALFA survey.
We have obtained spectra of the lone H II region in AGC 198691 with the new high-throughput
KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m as well as with the Blue
Channel spectrograph on the MMT 6.5-m telescope. These observations enable the measurement of the
temperature-sensitive [O III]4363 line and hence the determination of a \direct" oxygen abundance
for AGC 198691. We nd this system to be an extremely metal-decient (XMD) system with an
oxygen abundance of 12+log(O/H) = 7.02 0.03, making AGC 198691 the lowest-abundance starforming
galaxy known in the local universe. Two of the ve lowest-abundance galaxies known have
been discovered by the ALFALFA blind H I survey; this high yield of XMD galaxies represents a
paradigm shift in the search for extremely metal-poor galaxies.
A statistical analysis_of_the_accuracy_of_the_digitized_magnitudes_of_photome...Sérgio Sacani
We present a statistical analysis of the accuracy of the digitized magnitudes of photometric plates on
the time scale of decades. In our examination of archival Johnson B photometry from the Harvard
DASCH archive, we nd a median RMS scatter of lightcurves of order 0.15mag over the range B
9 17 for all calibrations. Slight underlying systematics (trends or
ux discontinuities) are on a level
of . 0:2mag per century (1889{1990) for the majority of constant stars. These historic data can
be unambiguously used for processes that happen on scales of magnitudes, and need to be carefully
examined in cases approaching the noise
oor. The characterization of these limits in photometric
stability may guide future studies in their use of plate archives. We explain these limitations for the
example case of KIC8462852, which has been claimed to dim by 0:16mag per century, and show that
this trend cannot be considered as signicant.
We describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This
satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the
Hubble Space Telescope’s Wide Field Camera 3 on UTC April 27, 2015 at 7.80±0.04 magnitudes
fainter than Makemake. It likely evaded detection in previous satellite searches due to a nearly edgeon
orbital configuration, placing it deep within the glare of Makemake during a substantial fraction
of its orbital period. This configuration would place Makemake and its satellite near a mutual event
season. Insufficient orbital motion was detected to make a detailed characterization of its orbital
properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary
analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days, and
must have a semi-major axis &21,000 km. We find that the properties of Makemake’s moon suggest
that the majority of the dark material detected in the system by thermal observations may not reside
on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform
dark surface. This “dark moon hypothesis” can be directly tested with future JWST observations.
We discuss the implications of this discovery for the spin state, figure, and thermal properties of
Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
The fornax deep_survey_with_vst_i_the_extended_and_diffuse_stellar_halo_of_ng...Sérgio Sacani
We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep
Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside
two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that
the core of the Fornax cluster is characterised by a very extended and diffuse envelope surrounding
the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼ 192 kpc)
from the galaxy center and down to μg ∼ 31 mag arcsec−2 in the g band. The deep photometry
allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399
and towards NGC 1387. By analyzing the integrated colors of this feature, we argue that it
could be due to the ongoing interaction between the two galaxies, where the outer envelope of
NGC 1387 on its east side is stripped away. By fitting the light profile, we found that exists a
physical break radius in the total light distribution at R = 10 arcmin (∼ 58 kpc) that sets the
transition region between the bright central galaxy and the outer exponential halo, and that the
stellar halo contributes for 60% of the total light of the galaxy (Sec. 3.5). We discuss the main
implications of this work on the build-up of the stellar halo at the center of the Fornax cluster.
By comparing with the numerical simulations of the stellar halo formation for the most massive
BCGs (i.e. 13 < logM200/M⊙ < 14), we find that the observed stellar halo mass fraction is
consistent with a halo formed through the multiple accretion of progenitors with stellar mass in
the range 108 − 1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through
a major merging event. The absence of a significant number of luminous stellar streams and
tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early
formation epoch. Therefore, differently from the Virgo cluster, the extended stellar halo around
NGC 1399 is characterised by a more diffuse and well-mixed component, including the ICL.
Magnetic interaction of_a_super_cme_with_the_earths_magnetosphere_scenario_fo...Sérgio Sacani
Solar eruptions, known as Coronal Mass Ejections (CMEs), are
frequently observed on our Sun. Recent Kepler observations of super
ares
on G-type stars have implied that so called super-CMEs, possessing kinetic
energies 10 times of the most powerful CME event ever observed on the Sun,
could be produced with a frequency of 1 event per 800-2000 yr on solar-
like slowly rotating stars. We have performed a 3D time-dependent global
magnetohydrodynamic simulation of the magnetic interaction of such a CME
cloud with the Earth's magnetosphere. We calculated the global structure
of the perturbed magnetosphere and derive the latitude of the open-closed
magnetic eld boundary. We also estimated energy
uxes penetrating the
Earth's ionosphere and discuss the consequences of energetic particle
uxes
on biological systems on early Earth.
Stellar-like objects with effective temperatures of 2700K and below are referred to as
20 "ultracool dwarfs"1. This heterogeneous group includes both extremely low-mass stars
21 and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion),
22 and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on
23 the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for
24 ultracool dwarfs predicts a large, but heretofore undetected, population of close-in
25 terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable
26 volatile-rich Earth-sized planets7. Here we report the discovery of three short-period
27 Earth-sized planets transiting an ultracool dwarf star 12 parsecs away. The inner two
28 planets receive four and two times the irradiation of Earth, respectively, placing them
29 close to the inner edge of the habitable zone of the star8. Eleven orbits remain possible
30 for the third planet based on our data, the most likely resulting in an irradiation
31 significantly smaller than Earth's. The infrared brightness of the host star combined
32 with its Jupiter-like size offer the possibility of constraining the composition and
33 thoroughly characterizing the atmospheric properties of the components of this nearby
34 planetary system, notably to detect potential biosignatures.
Direct Measure of Radiative And Dynamical Properties Of An Exoplanet AtmosphereSérgio Sacani
Two decades after the discovery of 51Pegb, the formation processes and atmospheres of short-period gas giants
remain poorly understood. Observations of eccentric systems provide key insights on those topics as they can
illuminate how a planet’s atmosphere responds to changes in incident flux. We report here the analysis of multi-day
multi-channel photometry of the eccentric (e ~ 0.93) hot Jupiter HD80606b obtained with the Spitzer Space
Telescope. The planet’s extreme eccentricity combined with the long coverage and exquisite precision of new
periastron-passage observations allow us to break the degeneracy between the radiative and dynamical timescales
of HD80606b’s atmosphere and constrain its global thermal response. Our analysis reveals that the atmospheric
layers probed heat rapidly (∼4 hr radiative timescale) from<500 to 1400 K as they absorb ~20% of the incoming
stellar flux during the periastron passage, while the planet’s rotation period is 93 35
85
-
+ hr, which exceeds the predicted
pseudo-synchronous period (40 hr).
Key words: methods: numerical – planet–star interactions – planets and satellites: atmospheres – planets and
satellites: dynamical evolution and stability – planets and satellites: individual (HD 80606 b) – techniques:
photometric
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
Young remmants of_type_ia_supernovae_and_their_progenitors_a_study_of_snr_g19_03Sérgio Sacani
Type Ia supernovae, with their remarkably homogeneous light curves and spectra, have been used as
standardizable candles to measure the accelerating expansion of the Universe. Yet, their progenitors
remain elusive. Common explanations invoke a degenerate star (white dwarf) which explodes upon
reaching close to the Chandrasekhar limit, by either steadily accreting mass from a companion star
or violently merging with another degenerate star. We show that circumstellar interaction in young
Galactic supernova remnants can be used to distinguish between these single and double degenerate
progenitor scenarios. Here we propose a new diagnostic, the Surface Brightness Index, which can
be computed from theory and compared with Chandra and VLA observations. We use this method
to demonstrate that a double degenerate progenitor can explain the decades-long
ux rise and size
increase of the youngest known Galactic SNR G1.9+0.3. We disfavor a single degenerate scenario.
We attribute the observed properties to the interaction between a steep ejecta prole and a constant
density environment. We suggest using the upgraded VLA to detect circumstellar interaction in
the remnants of historical Type Ia supernovae in the Local Group of galaxies. This may settle the
long-standing debate over their progenitors.
Subject headings: ISM: supernova remnants | radio continuum: general | X-rays: general | bi-
naries: general | circumstellar matter | supernovae: general | ISM: individual
objects(SNR G1.9+0.3)
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
As lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant
effects on climate and habitability over long timescales. Here we explore a specific case, Kepler-62f (Borucki et al.,
2013), a potentially habitable planet in a five-planet system with a K2V host star. N-body integrations reveal the
stable range of initial eccentricities for Kepler-62f is 0.00 £ e £ 0.32, absent the effect of additional, undetected
planets. We simulate the tidal evolution of Kepler-62f in this range and find that, for certain assumptions, the planet
can be locked in a synchronous rotation state. Simulations using the 3-D Laboratoire de Me´te´orologie Dynamique
(LMD) Generic global climate model (GCM) indicate that the surface habitability of this planet is sensitive to
orbital configuration.With 3 bar of CO2 in its atmosphere, we find that Kepler-62f would only be warm enough for
surface liquid water at the upper limit of this eccentricity range, providing it has a high planetary obliquity
(between 60 and 90). A climate similar to that of modern-day Earth is possible for the entire range of stable
eccentricities if atmospheric CO2 is increased to 5 bar levels. In a low-CO2 case (Earth-like levels), simulations
with version 4 of the Community Climate System Model (CCSM4) GCM and LMD Generic GCM indicate that
increases in planetary obliquity and orbital eccentricity coupled with an orbital configuration that places the
summer solstice at or near pericenter permit regions of the planet with above-freezing surface temperatures. This
may melt ice sheets formed during colder seasons. If Kepler-62f is synchronously rotating and has an ocean, CO2
levels above 3 bar would be required to distribute enough heat to the nightside of the planet to avoid atmospheric
freeze-out and permit a large enough region of open water at the planet’s substellar point to remain stable. Overall,
we find multiple plausible combinations of orbital and atmospheric properties that permit surface liquid water on
Kepler-62f. Key Words: Extrasolar planets—Habitability—Planetary environments. Astrobiology 16, xxx–xxx.
The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are
key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it
is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the
Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found
together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples,
a cometary origin was deduced from the 13C isotopic signature. We report the presence of volatile glycine
accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by
the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the
Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result
demonstrates that comets could have played a crucial role in the emergence of life on Earth.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
Extensive Noachian fluvial systems in Arabia Terra: Implications for early Ma...Sérgio Sacani
Valley networks are some of the strongest lines of evidence for
extensive fluvial activity on early (Noachian; >3.7 Ga) Mars. However,
their purported absence on certain ancient terrains, such as
Arabia Terra, is at variance with patterns of precipitation as predicted
by “warm and wet” climate models. This disagreement has contributed
to the development of an alternative “icy highlands” scenario,
whereby valley networks were formed by the melting of highland ice
sheets. Here, we show through regional mapping that Arabia Terra
shows evidence for extensive networks of sinuous ridges. We interpret
these ridge features as inverted fluvial channels that formed in
the Noachian, before being subject to burial and exhumation. The
inverted channels developed on extensive aggrading flood plains. As
the inverted channels are both sourced in, and traverse across, Arabia
Terra, their formation is inconsistent with discrete, localized sources
of water, such as meltwater from highland ice sheets. Our results are
instead more consistent with an early Mars that supported widespread
precipitation and runoff.
Martian soil as revealed by ground-penetrating radar at the Tianwen-1 landing...Sérgio Sacani
Much of the Martian surface is covered by a weathering layer (regolith or soil) produced
by long-term surface processes such as impact gardening, eolian erosion, water weathering,
and glacial modifications. China’s first Martian mission, Tianwen-1, employed the Mars
Rover Penetrating Radar (RoPeR) to unveil the detailed structure of the regolith layer and
assess its loss tangent. The RoPeR radargram revealed the local regolith layer to be highly
heterogeneous and geologically complex and characterized by structures that resemble partial
or complete crater walls and near-surface impact lenses at a very shallow depth. However,
comparable radar data from the Lunar far side are rather uniform, despite the two surfaces
being geologically contemporary. The close-to-surface crater presented in this study shows
no detectable surface expression, which suggests an accelerated occultation rate for small
craters on the surface of Mars as compared to the rate on the Moon. This is probably due to
the relentless eolian processes on the Martian surface that led to the burial of the crater and
thus shielded it from further erosion. The high loss tangent indicates that the regolith at the
Tianwen-1 landing site is not dominated by water ice.
Modern water at low latitudes on Mars: Potential evidence from dune surfacesSérgio Sacani
Landforms on the Martian surface are critical to understanding the nature of surface processes in the recent
past. However, modern hydroclimatic conditions on Mars remain enigmatic, as explanations for the formation
of observed landforms are ambiguous. We report crusts, cracks, aggregates, and bright polygonal ridges on the
surfaces of hydrated salt-rich dunes of southern Utopia Planitia (~25°N) from in situ exploration by the Zhurong
rover. These surface features were inferred to form after 1.4 to 0.4 million years ago. Wind and CO2 frost processes can be ruled out as potential mechanisms. Instead, involvement of saline water from thawed frost/snow is
the most likely cause. This discovery sheds light on more humid conditions of the modern Martian climate and
provides critical clues to future exploration missions searching for signs of extant life, particularly at low latitudes with comparatively warmer, more amenable surface temperatures.
Different Martian Crustal Seismic Velocities across the Dichotomy Boundary fr...Sérgio Sacani
Article This article is protected by copyright. All rights reserved.
Abstract
We have observed both minor-arc (R1) and major-arc (R2) Rayleigh waves for the largest marsquake (magnitude
of 4.7 ± 0.2) ever recorded. Along the R1 path (in the lowlands), inversion results show that a simple, two-layer
model with an interface located at 21 - 29 km and an upper crustal shear-wave velocity of 3.05 - 3.17 km/s can fit the
group velocity measurements. Along the R2 path, observations can be explained by upper crustal thickness models
constrained from gravity data and upper crustal shear-wave velocities of 2.61 - 3.27 km/s and 3.28 - 3.52 km/s in the
lowlands and highlands, respectively. The shear-wave velocity being faster in the highlands than in the lowlands
indicates the possible existence of sedimentary rocks, and relatively higher porosity in the lowlands.
The surface of Pluto is more geologically diverse and dynamic than had been expected,
but the role of its tenuous atmosphere in shaping the landscape remains unclear. We
describe observations from the New Horizons spacecraft of regularly spaced, linear ridges
whose morphology, distribution, and orientation are consistent with being transverse
dunes. These are located close to mountainous regions and are orthogonal to nearby wind
streaks. We demonstrate that the wavelength of the dunes (~0.4 to 1 kilometer) is best
explained by the deposition of sand-sized (~200 to ~300 micrometer) particles of methane
ice in moderate winds (<10 meters per second). The undisturbed morphology of the dunes,
and relationships with the underlying convective glacial ice, imply that the dunes have
formed in the very recent geological past.
Timing of oceans on Mars from shoreline deformationSérgio Sacani
Widespread evidence points to the existence of an ancient Martian
ocean1–8. Most compelling are the putative ancient shorelines in
the northern plains2,7
. However, these shorelines fail to follow
an equipotential surface, and this has been used to challenge the
notion that they formed via an early ocean9
and hence to question
the existence of such an ocean. The shorelines’ deviation from a
constant elevation can be explained by true polar wander occurring
after the formation of Tharsis10, a volcanic province that dominates
the gravity and topography of Mars. However, surface loading from
the oceans can drive polar wander only if Tharsis formed far from
the equator10, and most evidence indicates that Tharsis formed near
the equator11–15, meaning that there is no current explanation for
the shorelines’ deviation from an equipotential that is consistent
with our geophysical understanding of Mars. Here we show that
variations in shoreline topography can be explained by deformation
caused by the emplacement of Tharsis. We find that the shorelines
must have formed before and during the emplacement of Tharsis,
instead of afterwards, as previously assumed. Our results imply that
oceans on Mars formed early, concurrent with the valley networks15,
and point to a close relationship between the evolution of oceans
on Mars and the initiation and decline of Tharsis volcanism, with
broad implications for the geology, hydrological cycle and climate
of early Mars.
The habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
Artigo relata como a Terra sofreu com os impactos de ateroides a 4 bilhões de anos atrás, e como a superfície do planeta foi remodelada e os oceanos formados.
A large impact crater beneath Hiawatha Glacier in northwest GreenlandSérgio Sacani
We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impact- related grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron aster- oid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet.
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
Venus and Earth have remarkably diferent
surface conditions, yet the lithospheric
thickness and heat fow on Venus may be
Earth-like. This fnding supports a tectonic
regime with limited surface mobility and
dominated by intrusive magmatism.
Similar to Tsunami wave extensively_resurfaced_the_shorelines_of_an_early_martian_ocean (20)
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.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
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.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
This pdf is about the Schizophrenia.
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A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
1. 1Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
www.nature.com/scientificreports
Tsunami waves extensively
resurfaced the shorelines of an
early Martian ocean
J. Alexis P. Rodriguez1,2
,Alberto G. Fairén3,4
, Kenneth L. Tanaka5
, Mario Zarroca6
,
Rogelio Linares6
,Thomas Platz1,7,#
,Goro Komatsu8
, Hideaki Miyamoto9
, Jeffrey S. Kargel10
,
Jianguo Yan11
,Virginia Gulick2,12
, Kana Higuchi3
,Victor R. Baker10
& Natalie Glines2,12
It has been proposed that ~3.4 billion years ago an ocean fed by enormous catastrophic floods covered
most of the Martian northern lowlands. However, a persistent problem with this hypothesis is the
lack of definitive paleoshoreline features. Here, based on geomorphic and thermal image mapping in
the circum-Chryse and northwesternArabiaTerra regions of the northern plains, in combination with
numerical analyses, we show evidence for two enormous tsunami events possibly triggered by bolide
impacts, resulting in craters ~30 km in diameter and occurring perhaps a few million years apart.The
tsunamis produced widespread littoral landforms, including run-up water-ice-rich and bouldery lobes,
which extended tens to hundreds of kilometers over gently sloping plains and boundary cratered
highlands, as well as backwash channels where wave retreat occurred on highland-boundary surfaces.
The ice-rich lobes formed in association with the younger tsunami, showing that their emplacement
took place following a transition into a colder global climatic regime that occurred after the older
tsunami event.We conclude that, on early Mars, tsunamis played a major role in generating and
resurfacing coastal terrains.
The existence of an early Mars northern ocean1–7
remains a fundamental mystery8,9
. During the Hesperian
Period (~3.71 to 3.37 Ga; ages herein based on Neukum chronology as given in Michael)10
, Mars’ ancient hydro-
sphere was apparently cold-trapped within vast systems of subsurface aquifers underneath a thick, ice-rich
permafrost zone7
. Groundwater outbursts at the end of the Hesperian may have generated catastrophic floods
that produced an ocean in the northern lowlands, as evidenced by a deposit that covers most of this region
and generally exhibits a roughly topographically equipotential margin1–7,11,12
. Radar-sounding data are con-
sistent with the deposit being comprised of mostly water-ice13
. This deposit is identified as the Late Hesperian
lowland unit (lHl) on the latest geologic map of Mars14
. However, until now, the lack of wave-cut paleoshore-
line features9
and the presence of lobate margins8,12
appeared to be inconsistent with the Late Hesperian
paleo-ocean hypothesis. Our new geologic mapping in Chryse Planitia and northwestern Arabia Terra regions
reveals previously undistinguished, older and younger members of the unit (lHl1 and lHl2, respectively,
Fig. 1A). Both members are bounded by south-facing lobes that are typically tens of kilometers in length and
width; however, in Chryse Planitia these dimensions reach a few hundred kilometers in scale (Fig. 1B, Fig. S1).
The lobes reach upland boundary surfaces distributed between approximately − 4087 m and − 3191 m of elevation
1
Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ 85719-2395, USA. 2
NASA Ames
Research Center, Mail Stop 239-20, Moffett Field, CA, 94035, USA. 3
Department of Planetology and Habitability,
Centro de Astrobiología (CSIC-INTA), Madrid 28850, Spain. 4
Department of Astronomy, Cornell University, Ithaca,
NY 14850, USA. 5
Astrogeology Science Center, U.S. Geological Survey, Flagstaff, AZ 86001, USA. 6
External
Geodynamics and Hydrogeology Group, Department of Geology, Autonomous University of Barcelona, 08193
Bellaterra, Barcelona, Spain. 7
Planetary Sciences and Remote Sensing, Institute of Geological Sciences, Freie
Universität Berlin, 12249 Berlin, Germany. 8
International Research School of Planetary Sciences, Università
d’Annunzio, Viale Pindaro 42, 65127 Pescara, Italy. 9
The University Museum, University of Tokyo, 113-0033,
Japan. 10
Department of Hydrology & Water Resources, University of Arizona,Tucson, AZ 85721, USA. 11
State Key
Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan
430070,China. 12
SETI Institute, 189 BernardoAvenue, MountainView,CA 94043,USA. #
Present address: Max Planck
Institute forSolarSystem Research, Department “Planets andComets”,Justus-von-Liebig-Weg 3, 37077Göttingen,
Germany.Correspondence and requests for materials should be addressed to J.A.P.R. (email: alexis@psi.edu)
received: 27 November 2015
accepted: 08April 2016
Published: 19 May 2016
OPEN
2. www.nature.com/scientificreports/
2Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
(Fig. S2). These deposits embay dozens of streamlined promontories scattered over a surface area of ~570,000 km2
(Fig. 1B,C).
In THEMIS night-time infrared images, the upper reaches of the older deposit that were emplaced along
Arabia and Tempe Terrae (member lHl1 (Fig. 1A)) appear thermally bright (i.e., rocky exposures)15
and abruptly
transition upland-ward into thermally dark (i.e., fine-grained sediments)15
surfaces (e.g., Figs 2A,B and 3B).
Close-up views show that the bright surfaces consist of boulder deposits, with individual boulders typically meters
in diameter (Figs 2C and 3E, Fig. S3D). Exhumation of the boulder deposit from beneath ejecta blanket mate-
rials along impact crater rims (black arrows in Fig. 2B,C), as well as distinct onlapping contacts (e.g., Fig. S3C),
show that the deposit overlies the thermally dark surfaces consisting of finer-grained materials (e.g., Figs 2A,B
and 3B). Throughout spatially disconnected locations in the eastern part of northwestern Arabia Terra, the mar-
ginal parts of member lHl1 cover low-slope ramps that are extensively dissected by NNW-trending (Fig. S4A) sets
of aligned channels (e.g., Fig. 3A–D). These channels were first identified in Viking data (but only locally along
Arabia Terra in association with an older “lowland unit A”)1
.
Upslope flows leading to the emplacement of the lHl unit are implied by the highland-facing orientation of the
deposits’ lobes as well as their relief gains, which commonly are a few hundred meters (e.g., Fig. 1A,B, Figs. S5,
S6). These characteristics rule out emplacement by gravity-driven downslope moving flows such as debris, flood,
glacier and lava flows. Uphill unidirectional winds can generate elongate aeolian deposits known as wind streaks.
However, these deposits are largely composed of saltating sand-sized lithic particles that are deposited in scattered
patches on the lee sides of topographic obstacles (typically impact craters), exhibit surface bedforms, generally
cover hills and mesas situated along their paths, and mostly have length-to-width ratios >1 (ref. 16). In contrast,
the lobes of member lHl1 include boulders several meters in diameter (Figs 2C and 3E, Fig. S3D), and those of
member lHl2 appear to be mostly composed of water-ice6,12–14
. In addition, the lobes in both members diverge
around numerous mesas (e.g., Fig. 1C) as well as broad rises (e.g., Fig. S3), and have length-to-width ratios mostly
<1 (Fig. S1) (which is consistent with uphill flow along with substantial lateral spreading). Therefore, we propose
that the two unit lHl members represent deposits emplaced by highly energetic, sediment-rich tsunami waves that
originated from a Late Hesperian paleo-ocean.
In Deuteronilus Mensae, extensive troughs cut the boundary scarps covered by member lHl1. The troughs are
locally intruded by member lHl2 run-up lobes (e.g., Fig. 2D), indicating that they formed during the time interval
separating the two tsunami events. Active resurfacing leading to the formation of these troughs likely lasted a few
million years and could have been the result of Late Hesperian glacial erosion17
. Crater-count statistics show that,
Figure 1. (A) View of the circum-Chryse highland-lowland boundary region, which is made up of the Chryse
and Acidalia Planitiae lowlands and the Tempe, Xanthe, and Arabia Terrae highlands (inset shows region within
the planetwide context). The boundary is breached by the planet’s largest outflow channels (blue arrows). The
red and black lines trace the margins of Late Hesperian lowland members lHl1 and lHl2, respectively. (B) View
of Chryse and Acidalia Planitiae showing the distribution of streamlined promontories (green) buried by
these deposits. The base images for panels (A,B) are color-coded shaded-relief MOLA digital elevation models
(460 m/pixel). Credit: MOLA Science Team, MSS, JPL, NASA. (C) View of a streamlined promontory that is
embayed, and partly buried (e.g., black arrows), by member lHl2 materials. Part of HRSC image H1436_0000_
ND3 (12.5 m/pixel) centered at 30.3°N, 35.9°W, (http://hrscview.fu-berlin.de/cgi-bin/ion-p?page= product.
ion&image= 1436_0000), which is licensed under Attribution-ShareAlike 3.0 IGO license. The license terms
can be found on the following link: https://creativecommons.org/licenses/by-sa/3.0/igo/. Credit: ESA/DLR/FU
Berlin. We produced the mosaics and maps in this figure using Esri’s ArcGIS®10.3 software (http://www.esri.
com/software/arcgis).
3. www.nature.com/scientificreports/
3Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
Figure 2. (A) View of highland surfaces along the highland-lowland boundary in northwestern Arabia Terra,
which are embayed by the upper reaches of members lHl1 and lHl2. The red (lHl1) and orange (lHl2) lines show
contact sections mapped as certain. The yellow lines are zones where the contacts are obscured due to localized
resurfacing or mantling. Out of the total 4124 km length of these mapped contacts, 76% is certain and 23% is
uncertain. Part of THEMIS night-time infrared image mosaic (100 m/pixel) centered at 43°26′ N, 12°29′ E. Credit:
Christensen et al.32
. (B) Perspective close-up view on a system of mesas, which are partly covered by the upper
reaches of member lHl1. These deposits consist of thermally bright materials that pass upland-wards into thermally
dark surfaces. The black arrows show locations where the thermally dark materials are exhumed from beneath
the thermally bright materials by impact craters. Center location indicated by dot in panel A. Part of THEMIS
night-time infrared mosaic (100 m/pixel) centered at 45°45′N, 16°41′E. Credit: Christensen et al.32
. (C) Visible
light close-up view on one of the craters identified in panel (B). The impact crater’s inner wall shows the boulder
deposit (member lHl1) overlying an exhumed non-bouldery upper stratigraphy. The boulder deposit is also locally
covered by a non-bouldery ejecta blanket. The inset shows the view’s location along the crater’s northern margin.
Part of HiRISE image ESP_017355_2260 centered at 45.82°N 16.47°E (50 cm/pixel). Credit: NASA/JPL/University
of Arizona. (D) Close-up view of northeast Deuteronilus Mensae showing a low-angle ramp marked by backwash
channels (part of member lHl1), which is cut by a shallow trough. A lobe of member lHl2 can be observed to run up
the trough’s surface. The black arrow identifies a marginal compressional fold. Location is shown in panel (A). Part
of a CTX mosaic centered at 44°49′ N, 11°10′ E. Credit: NASA/JPL. The license terms can be found on the following
link: pds-imaging.jpl.nasa.gov/portal/mro_mission.html. We produced the mosaics and maps in this figure using
Esri’s ArcGIS®10.3 software (http://www.esri.com/software/arcgis).
4. www.nature.com/scientificreports/
4Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
while the deposits formed during the Late Hesperian Epoch, their absolute ages could differ as much as several
tens of millions of years (see supplementary crater statistics).
The boulder deposits of member lHl1 drape over, and therefore postdate, the incision of adjoining highland
channels (e.g., orange arrow in Fig. S3A), ruling out upland fluvial systems as possible discharge sources. Highly
energetic, boulder-rich tsunami fronts on Earth show diversion around topographic obstacles as they propagate
onshore18
. Similarly, member lHl1 boulder deposits exhibit well-defined landward lobate margins around broad
promontories (Fig. S3A–C). Member lHl1 boulders range from rounded to angular and are as much as ~10 m in
diameter (Figs 2C and 3E, Fig. S3D), which are also characteristics of some terrestrial tsunami deposits18
. Thus,
Figure 3. (A) View of Deuteronilus Mensae in northwestern Arabia Terra showing the distribution and
elevation ranges of ramp surfaces marked by backwash channels as well as the reconstructed location of the
paleoshoreline from which the older tsunami (member lHl1) propagated (see Fig. 4 and Fig. S4 for details on
paleoshoreline reconstructions). Shaded-relief MOLA digital elevation model (460 m/pixel). Credit: MOLA
Science Team, MSS, JPL, NASA. (B) Close-up view on panel (A) showing the distribution of some of the
channel-scoured, north-sloping highland mesas (blue areas). Channels occur on bright (i.e., higher thermal
inertia) surfaces, which abruptly transition (red line) in lower part of image to uplands covered by dark (lower
thermal inertia) materials. THEMIS night-time infrared image mosaic, context and location in panel A. Credit:
Christensen et al.32
. Example of channeled surface (C) displaying streamlined bars (D) made up of rounded
to angular boulders as much as ~10 m in diameter (yellow bars are 10 m in length) (E). (C–E), Parts of HiRISE
image ESP_028537_2270, 25 cm/pixel. Credit: NASA/JPL/University of Arizona.) We produced the mosaics and
maps in this figure using Esri’s ArcGIS®10.3 software (http://www.esri.com/software/arcgis).
5. www.nature.com/scientificreports/
5Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
we interpret the member lHl1 lobes as made up of lowland and boundary clastic materials that were captured and
transported by a tsunami wave, then beached farther inland as the wave lost its momentum.
Subsequently, we suggest that rapid gravity-forced backwash of the tsunami wave into the paleo-ocean dis-
sected the channel systems on the marginal parts of member lHl1 in the eastern part of northwestern Arabia Terra
(Fig. 3A–D). These channels have remarkable similarities to terrestrial tsunami backwash channels; including the
presence of aligned channel heads19
(black arrows in Fig. 3C), perpendicular orientations to the reconstructed
paleoshoreline19
(Fig. S4A), streamlined bars composed of reworked boulders20,21
(Fig. 3D,E), and widths ranging
between ~50 and ~200 m (refs 19,22) (Fig. 3C,D). Parker et al.23
observed a few of these parallel channel systems
in Arabia Terra using lower-resolution image data, and they also interpreted them as tsunami backwash channels.
The lower terminations of the proposed backwash channels are generally truncated by younger scarps
(Figs 2D and 3C, Fig. S4A). However, the identification of a possibly subaqueously emplaced sedimentary lobe
adjoining the lower reaches of a set of these channels located at ~− 3795 m in elevation (Fig. S4B) provides an
approximate upper boundary to the paleoshoreline from which the older tsunami propagated (Fig. 4A). The
lowest margins of the mapped lHl2 lobes are at ~− 4100 m in elevation (Fig. S2), which we have used as an upper
bound to the paleoshoreline elevation from which the younger tsunami propagated (Fig. 4B). The elevation differ-
ence between the two paleoshorelines implies a decrease in ocean level of ~300 m, which could have taken place
via evaporation/sublimation within several million years6
.
Based on these paleo-oceanographic reconstructions, we estimate that the areas inundated by the older and
younger tsunamis within the study region were ~8 × 105
km2
and ~1 × 106
km2
, respectively (Fig. S5). Measured
typical run-up distances are tens to a few hundred kilometers for both the older and younger tsunamis, and their
respective maxima reach ~529 km and ~650 km (Fig. S6). Overall, the morphometric characterizations of both
tsunamis are strikingly similar. The slightly larger inundation area that was apparently covered during the younger
event is consistent with the tsunami extending from a lower shoreline, and therefore, flowing over relatively smooth,
older ocean and tsunami deposits. These run-up distances and inundation areas are enormous by terrestrial stand-
ards, which explain why the backwash channels exhibit lengths of ~20 km, while some terrestrial examples of back-
wash channel lengths produced by much smaller tsunamis range between ~200 and ~300 m in length22
.
Our mapping (Fig. 1, Fig. S6) shows comparatively shorter run-up distances along the rougher and steeper cra-
tered topography of the Arabia Terra boundary terrains, indicative of relatively lower wave heights and velocities,
Figure 4. (A) Late Hesperian ocean with a paleoshoreline elevation close to − 3795 m (light blue), and
estimated extent of the older tsunami (dotted surface). (B) Late Hesperian ocean with a paleoshoreline elevation
close to − 4100 m (dark blue), and estimated extent of the younger tsunami (dotted surface). The ocean margins
were reconstructed by tracing the estimated paleoshoreline elevations, while carefully interpolating across
topography generated by clearly younger resurfacing processes. The tsunami margins were produced using
the lHl unit’s lobes extending from the projected paleoshoreline elevations. Areas marked in red represent the
locations of streamlined promontories in Chryse Planitia, which were embayed, and/or buried, by materials
emplaced during each of the tsunami events. Topography in (A,B) from shaded-relief MOLA digital elevation
model (460 m/pixel). Credit: MOLA Science Team, MSS, JPL, NASA. We produced the mosaics and maps in
this figure using Esri’s ArcGIS®10.3 software (http://www.esri.com/software/arcgis).
6. www.nature.com/scientificreports/
6Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
as predicted by tsunami numerical simulations24
. These simulations also indicate that as the waves overflowed
the Arabia Terra cratered boundary, their velocities would have abruptly dropped below the ~1 m/s threshold
required to move multi-meter-scale boulders, explaining the occurrence of the boulder deposits in the region
(Figs 2C and 3E, Fig. S3D). On the other hand, the more gentle slopes in Chryse Planitia would have resulted in
a more gradual decrease in wave velocity, leading to the emplacement of more sorted sedimentary lobes, with
their distal-most areas primarily consisting of finer-grained sediments. In addition, prior to their inundation
by tsunami waves, the highland boundary surfaces were likely covered by extensive boulder fields, which would
have been captured and redistributed by the waves, which is also another important factor accounting for the
regional prevalence of boulder-rich lobes. In Chryse Planitia the tsunamis would have mostly propagated over
gently-sloping plains that were largely made up of less bouldery outflow channel sedimentary deposits14
.
The simulations also show that bolide impacts causing craters ~30 km in diameter would have generated tsu-
nami waves with typical onshore heights of ~50 m and local variations from ~10 m to as much as ~120 m (ref. 24).
Using run-up distances measured in 71 topographic profiles (Fig. S6), we have calculated the tsunami wave
heights and find that they reasonably match the simulations’ predicted ranges24
(see supplementary calculations).
In addition, whereas the simulations do not describe the hydrodynamic behavior of the backwash stage, the for-
mation of several marine impact craters on Earth has also resulted in documented tsunami backwash channels25
.
Using the surface area of the paleo-ocean’s region included in the numerical simulation by Iijima et al.24
(i.e.,
~4.5 × 106
km2
) and the crater production function of Ivanov26
, we find that ~23 marine impact craters ≥ 30 km
in diameter would have formed within this part of Mars during the Late Hesperian Epoch (3.61–3.37 Ga)10,27
. Of
these, 7 fit in the diameter range of 30–35 km, which was used in the tsunami simulations24
. The prediction is that,
within the particular region of the ocean analyzed here, on average about 2 impact craters ~30 km in diameter
formed every 30 million years during this time period. Therefore, within statistical constraints for the deposits’
surface ages and for crater production rates, impacts can account for generation of both lHl members as tsunami
deposits (see supplementary crater statistics).
Briny aqueous chemistry models show that the ocean could have remained in liquid form over millions of
years, and consequently mostly free of an ice cover even during cryogenic climatic conditions28
. Another geo-
logic scenario invokes the formation of an ice-covered ocean soon after the ocean’s emplacement6
. However, no
numerical simulations have been performed to detail the behavior of impact-related tsunamis24
on these types of
Martian marine environments.
High rates of marine, and subsequent periglacial6,12,14
resurfacing, likely reduced the topography of the
tsunami-generating crater structures. Such resurfacing can also explain the lack of well-preserved impact craters
predating the Amazonian Period in the northern lowlands12
. The frequency rate of ~30 km in diameter impact
craters for the entire ocean’s surface area (~24 × 106
km2
, as determined by Head et al.3
) is one every 2.7 million
years during the Late Hesperian. Although we have only identified evidence for two tsunami events in our study
area, other regions in the northern plains likely experienced similar tsunami-related coastal resurfacing, perhaps
associated with other impacts, huge landslides, or large marsquakes. Older but less extensive tsunami deposits
may have been completely resurfaced by more recent events with similar run-up distances. Thus, the mapped
tsunami margins comprise only the largest magnitude tsunami events located at the highest elevations.
Many of the lHl1 lobes are mostly made up of lithic deposits and exhibit backwash modifications. In contrast,
the landward-facing lobate termini of unit lHl2 lack evidence indicative of a backwash phase subsequent to their
emplacement. Like on Earth, the absence of backwash features associated with these flows could have been the
result of the waves transitioning into sub-aerial sediment-laden slurry flows extending over low gradient sur-
faces29,30
(supplementary calculations), which can also explain the presence of possible contractional folds along
the margins of some of the member’s lobes (e.g., black arrow in Fig. 2D). However, the lHl2 lobes appear to be
mostly composed of water-ice6,12–14
, suggesting that the transition into slurry likely involved the formation and
incorporation of a significant proportion of ice particles. In May 2013, the Saskatchewan Water Security Agency
filmed an ice surge in the Codette Reservoir near Nipawin, Saskatchewan, Canada. The surge comprises a spec-
tacular terrestrial analog of rarely observed catastrophic ice-rich flows leading to the emplacement of enormous
lobate fronts, which are remarkably similar to those of member lHl2 (video link included in ref. 31).We propose
that these morphologic differences might be linked to colder environmental conditions following the first tsu-
nami event.
Our mapping of two unit lHl members as tsunami lobes is consistent with the occurrence of two paleoshore-
line levels of a receding Martian northern plains ocean during the Late Hesperian ( Fig. 4, Fig. S5). However,
resurfacing by the tsunami waves has obscured the paleoshorelines, thus making rigorous testing of their equi-
potentiality impossible.
Mapping Methodology
Mapping in this investigation was performed using Esri’s ArcGIS®10.3 software (http://www.esri.com/software/
arcgis). Embayment and overlapping relationships leading to the recognition of the outer margins of members
lHl1 and lHl2 involved an integrated analysis of (1) thermal infrared image data (i.e., Mars Odyssey Thermal
Emission Imaging System (THEMIS) night-time and day-time infrared image mosaics (100 m per pixel)), (2)
visible image data (i.e., Mars Reconnaissance Orbiter Context Camera (CTX, (5.15–5.91 m/pixel)) images, and
(3) Mars Global Surveyor Mars Orbital Laser Altimeter (MOLA, ~460 m/pixel horizontal and ~1 m vertical res-
olution) digital elevation models. In some areas, contacts are buried underneath ejecta blanket materials or are
locally resurfaced; we mapped these sections as uncertain contacts (Fig. 2A).
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Acknowledgements
Funding for JAPR was provided by NASA’s Planetary Geologic and Geophysics Program, NASA NPP and
KAKENHI 25120006. KLT was also funded by NASA’s Planetary Geologic and Geophysics Program. AGF was
supported by the Project “icyMARS”, funded by the European Research Council, Starting Grant No. 307496.
TP was supported by a DFG Grant (PL613/2-1). VCG was funded by MRO HiRISE Co-Investigator funds. HM
was funded by KAKENHI 25120006. Publications costs were covered by the Project “icyMARS”, funded by the
European Research Council, Starting Grant No. 307496. We are thankful to Alexander Cox for his valuable
editing.
AuthorContributions
J.A.P.R. developed the core hypotheses, wrote most of the main text, prepared Figures 1–4, and the supplementary
Figures. A.G.F. and K.L.T. contributed to the overall design and structure of the manuscript. A.G.F. conceived and
wrote text related to ocean liquid stability under freezing climatic conditions. K.L.T. produced the supplementary
crater statistics. M.Z., R.L., H.M. and J.Y. developed the numerical supplement. T.P. estimated the production
rates for impact craters ≥ 30 km in diameter. G.K. contributed to the comparative planetology and tsunami wave
propagation discussions. J.S.K., V.G., V.R.B. and N.G. contributed to the development of specific aspects of the
proposed hypotheses. K.H. produced GIS analyses used in the supplementary figures. All authors discussed the data
and reviewed the manuscript.
8. www.nature.com/scientificreports/
8Scientific Reports | 6:25106 | DOI: 10.1038/srep25106
Additional Information
Supplementary information accompanies this paper at http://www.nature.com/srep
Competing financial interests: The authors declare no competing financial interests.
How to cite this article: Rodriguez, J. A. P. et al. Tsunami waves extensively resurfaced the shorelines of an early
Martian ocean. Sci. Rep. 6, 25106; doi: 10.1038/srep25106 (2016).
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