The era of helicopter-based surveys on Mars has already begun, creating opportunities for future aerial science
investigations with a range of instruments. We argue that magnetometer-based studies can make use of aerial
technology to answer some of the key questions regarding early Mars evolution. As such, we discuss mission
concepts for a helicopter equipped with a magnetometer on Mars, measurements it would provide, and survey
designs that could be implemented. For a range of scenarios, we build magnetization models and test how well
structures can be resolved using a range of different inversion approaches. With this work, we provide modeling
ground work and recommendations to plan the future of aerial Mars exploration.
An ESA Study For The Search For Life On MarsFaith Brown
This document proposes a hypothetical strategy to search for life on Mars using robotic missions. It discusses the following key points:
1. Mars and early Earth had similar environments that could have supported the development of life, so life may have arisen on Mars as well in a primitive prokaryotic form.
2. A robotic mission should carefully select landing sites with good exobiological potential to find chemical or morphological biosignatures. Samples would be collected and analyzed using integrated instruments on a lander and rover.
3. The goal is to obtain environmental data, look for microscopic evidence of life, analyze biogeochemistry, and identify potential niches for extant life to increase the chances of detecting past or present
Beyond the Drake Equation: A Time-Dependent Inventory of Habitable Planets an...Sérgio Sacani
We introduce a mathematical framework for statistical exoplanet population and astrobiology studies
that may help directing future observational efforts and experiments. The approach is based on a
set of differential equations and provides a time-dependent mapping between star formation, metal
enrichment, and the occurrence of exoplanets and potentially life-harboring worlds over the chemopopulation history of the solar neighborhood. Our results are summarized as follows: 1) the formation
of exoplanets in the solar vicinity was episodic, starting with the emergence of the thick disk about
11 Gyr ago; 2) within 100 pc from the Sun, there are as many as 11, 000 (η⊕/0.24) Earth-size planets
in the habitable zone (“temperate terrestrial planets” or TTPs) of K-type stars. The solar system is
younger than the median TTP, and was created in a star formation surge that peaked 5.5 Gyr ago and
was triggered by an external agent; 3) the metallicity modulation of the giant planet occurrence rate
results in a later typical formation time, with TTPs outnumbering giant planets at early times; 4) the
closest, life-harboring Earth-like planet would be ∼
< 20 pc away if microbial life arose as soon as it did
on Earth in ∼
> 1% of the TTPs around K stars. If simple life is abundant (fast abiogenesis), it is also
old, as it would have emerged more than 8 Gyr ago in about one third of all life-bearing planets today.
Older Earth analogs are more likely to have developed sufficiently complex life capable of altering the
environment and producing detectable oxygenic biosignatures.
The Dynamical Consequences of a Super-Earth in the Solar SystemSérgio Sacani
Placing the architecture of the solar system within the broader context of planetary architectures is one of the
primary topics of interest within planetary science. Exoplanet discoveries have revealed a large range of system
architectures, many of which differ substantially from the solar system’s model. One particular feature of exoplanet
demographics is the relative prevalence of super-Earth planets, for which the solar system lacks a suitable analog,
presenting a challenge to modeling their interiors and atmospheres. Here we present the results of a large suite of
dynamical simulations that insert a hypothetical planet in the mass range 1–10 M⊕ within the semimajor axis range
2–4 au, between the orbits of Mars and Jupiter. We show that, although the system dynamics remain largely
unaffected when the additional planet is placed near 3 au, Mercury experiences substantial instability when the
additional planet lies in the range 3.1–4.0 au, and perturbations to the Martian orbit primarily result when the
additional planet lies in the range 2.0–2.7 au. We further show that, although Jupiter and Saturn experience
relatively small orbital perturbations, the angular momentum transferred to the ice giants can result in their ejection
from the system at key resonance locations of the additional planet. We discuss the implications of these results for
the architecture of the inner and outer solar system planets, and for exoplanetary systems
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
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.
The MESSENGER mission aims to study Mercury through flybys in 2008-2009 and orbital observations beginning in 2011. It launched in 2004 and will use gravity assists at Earth and Venus to reach Mercury's orbit. The spacecraft faces challenges from Mercury's intense solar radiation and requires a large velocity change to achieve orbit. It carries 7 miniaturized instruments to characterize Mercury's composition, geology, magnetic field, exosphere, and magnetosphere. The flybys and orbital phase aim to address outstanding questions about Mercury's formation and evolution.
Digital and global lithologic mapping of the Moon at a 1:2,500,000 scaleSérgio Sacani
This document summarizes a new 1:2,500,000 scale lithologic map of the Moon created by researchers in China. The map was created using data from Chinese lunar exploration missions, other international missions, and samples returned by Apollo, Luna and Chinese missions. It represents an improvement over previous maps by distinguishing new lithological units and clarifying relationships between different rock types observed on the lunar surface and in samples. The mapping effort provides a comprehensive database of lunar surface compositions to further the understanding of the Moon's geological evolution.
An ESA Study For The Search For Life On MarsFaith Brown
This document proposes a hypothetical strategy to search for life on Mars using robotic missions. It discusses the following key points:
1. Mars and early Earth had similar environments that could have supported the development of life, so life may have arisen on Mars as well in a primitive prokaryotic form.
2. A robotic mission should carefully select landing sites with good exobiological potential to find chemical or morphological biosignatures. Samples would be collected and analyzed using integrated instruments on a lander and rover.
3. The goal is to obtain environmental data, look for microscopic evidence of life, analyze biogeochemistry, and identify potential niches for extant life to increase the chances of detecting past or present
Beyond the Drake Equation: A Time-Dependent Inventory of Habitable Planets an...Sérgio Sacani
We introduce a mathematical framework for statistical exoplanet population and astrobiology studies
that may help directing future observational efforts and experiments. The approach is based on a
set of differential equations and provides a time-dependent mapping between star formation, metal
enrichment, and the occurrence of exoplanets and potentially life-harboring worlds over the chemopopulation history of the solar neighborhood. Our results are summarized as follows: 1) the formation
of exoplanets in the solar vicinity was episodic, starting with the emergence of the thick disk about
11 Gyr ago; 2) within 100 pc from the Sun, there are as many as 11, 000 (η⊕/0.24) Earth-size planets
in the habitable zone (“temperate terrestrial planets” or TTPs) of K-type stars. The solar system is
younger than the median TTP, and was created in a star formation surge that peaked 5.5 Gyr ago and
was triggered by an external agent; 3) the metallicity modulation of the giant planet occurrence rate
results in a later typical formation time, with TTPs outnumbering giant planets at early times; 4) the
closest, life-harboring Earth-like planet would be ∼
< 20 pc away if microbial life arose as soon as it did
on Earth in ∼
> 1% of the TTPs around K stars. If simple life is abundant (fast abiogenesis), it is also
old, as it would have emerged more than 8 Gyr ago in about one third of all life-bearing planets today.
Older Earth analogs are more likely to have developed sufficiently complex life capable of altering the
environment and producing detectable oxygenic biosignatures.
The Dynamical Consequences of a Super-Earth in the Solar SystemSérgio Sacani
Placing the architecture of the solar system within the broader context of planetary architectures is one of the
primary topics of interest within planetary science. Exoplanet discoveries have revealed a large range of system
architectures, many of which differ substantially from the solar system’s model. One particular feature of exoplanet
demographics is the relative prevalence of super-Earth planets, for which the solar system lacks a suitable analog,
presenting a challenge to modeling their interiors and atmospheres. Here we present the results of a large suite of
dynamical simulations that insert a hypothetical planet in the mass range 1–10 M⊕ within the semimajor axis range
2–4 au, between the orbits of Mars and Jupiter. We show that, although the system dynamics remain largely
unaffected when the additional planet is placed near 3 au, Mercury experiences substantial instability when the
additional planet lies in the range 3.1–4.0 au, and perturbations to the Martian orbit primarily result when the
additional planet lies in the range 2.0–2.7 au. We further show that, although Jupiter and Saturn experience
relatively small orbital perturbations, the angular momentum transferred to the ice giants can result in their ejection
from the system at key resonance locations of the additional planet. We discuss the implications of these results for
the architecture of the inner and outer solar system planets, and for exoplanetary systems
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
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.
The MESSENGER mission aims to study Mercury through flybys in 2008-2009 and orbital observations beginning in 2011. It launched in 2004 and will use gravity assists at Earth and Venus to reach Mercury's orbit. The spacecraft faces challenges from Mercury's intense solar radiation and requires a large velocity change to achieve orbit. It carries 7 miniaturized instruments to characterize Mercury's composition, geology, magnetic field, exosphere, and magnetosphere. The flybys and orbital phase aim to address outstanding questions about Mercury's formation and evolution.
Digital and global lithologic mapping of the Moon at a 1:2,500,000 scaleSérgio Sacani
This document summarizes a new 1:2,500,000 scale lithologic map of the Moon created by researchers in China. The map was created using data from Chinese lunar exploration missions, other international missions, and samples returned by Apollo, Luna and Chinese missions. It represents an improvement over previous maps by distinguishing new lithological units and clarifying relationships between different rock types observed on the lunar surface and in samples. The mapping effort provides a comprehensive database of lunar surface compositions to further the understanding of the Moon's geological evolution.
High-altitude nuclear explosions in the late 1950s and early 1960s produced unintended effects on space weather through the creation of artificial radiation belts and electromagnetic pulses (EMPs). These explosions generated radiation that damaged satellites and could potentially damage modern electronics over large areas. Other anthropogenic impacts on space weather discussed include chemical releases, ionosphere heating experiments, and interactions between VLF radio waves and radiation belts. While the effects of human activities are difficult to separate from natural space weather drivers, modern technology has increased humanity's influence on the near-Earth space environment.
The hazardous km-sized NEOs of the next thousands of yearsSérgio Sacani
This document discusses methods for assessing the long-term impact risk of km-sized near-Earth objects (NEOs) over thousands of years. It analyzes the evolution of the Minimum Orbit Intersection Distance (MOID) between NEOs and Earth to identify objects that remain in close proximity for extended periods. It then estimates the probability of a deep Earth encounter during these low-MOID periods based on the growth of orbital uncertainties over time. This allows the authors to rank km-sized NEOs by their long-term impact hazard and identify targets that warrant further observation and analysis.
This document discusses how geomagnetic storms can affect marine archaeological surveys by introducing noise and masking spatial variations in Earth's magnetic field that are used to identify archaeological anomalies. The study analyzed 34 geomagnetic storms and found that their sudden onset signatures were indistinguishable from archaeological anomalies. Based on this, it is estimated that 89.7-100% of strong geomagnetic storms will generate signatures that could be misinterpreted as archaeological sites. The document recommends improved data collection and processing methods to better account for geomagnetic storms and improve precision in identifying archaeological resources.
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.
The Expansion of the X-Ray Nebula Around η CarSérgio Sacani
1. The author analyzes over 20 years of Chandra X-ray images to measure for the first time the expansion of the X-ray nebula around η Carinae.
2. A combined Chandra image reveals a faint, nearly uniform elliptical shell surrounding the X-ray bright ring, with a similar orientation and shape as the Homunculus nebula but about 3 times larger.
3. The author measures proper motions of brighter regions associated with the X-ray emitting ring, such as the S-ridge and W-arc. Motions are consistent with optical studies of ejecta from the 1840s Great Eruption.
In Situ Geophysical Exploration by Humans in Mars Analog EnvironmentsBrian Shiro
Presented on May 13, 2010 at the University of North Dakota's 997 symposium. Summarizes the research projects I carried out on two analog Mars missions in 2009 and 2010.
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU...Sérgio Sacani
This document summarizes observations from the Hubble Space Telescope of the young hot Neptune exoplanet AU Mic b, which orbits the nearby M dwarf star AU Mic. The observations aimed to detect atmospheric escape of neutral hydrogen through absorption in the stellar Lyman-alpha emission line. Two visits were obtained, one in 2020 and one in 2021, corresponding to transits of the planet. A stellar flare was observed and removed from the first visit data. In the second visit, absorption was detected in the blue wing of the Lyman-alpha line 2.5 hours before the white light transit, indicating the presence of high-velocity neutral hydrogen escaping the planet's atmosphere and traveling toward the observer. Estimates place the column density of this material
1) New data from the GRAIL gravity mission and LOLA altimetry is helping to determine the structure of the lunar highlands crust.
2) Preliminary GRAIL gravity models show noise levels are lower than expected, indicating signals exist at even shorter wavelengths than planned.
3) Combined analysis of gravity and topography data can provide insights into crustal thickness, elastic properties of the lithosphere, and the thermal state during and after bombardment.
Transit photometry has been the most successful exoplanet discovery method to date. It works by detecting the dimming of a star's light as a planet passes in front of it. From the transit light curve, properties of the planet like its radius and orbital parameters can be derived. However, transits have a low probability of being aligned with our line of sight. False positives from eclipsing binaries can also mimic transits, so follow-up observations are needed to confirm planetary discoveries. Past and current transit surveys have found over a hundred planets, and future surveys aim to detect smaller planets orbiting brighter stars.
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
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
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
La historia de la vida en la Tierra y en otras plataformas planetarios potenciales portadoras de vida están profundamente ligadas a la historia del Universo. Puesto que la vida, tal como la conocemos, se basa en elementos químicos forjados en estrellas pesadas moribundas, el Universo tiene que ser lo suficientemente antiguo para que las estrellas se formaran y evolucionaran. La teoría cosmológica actual indica que el Universo es de 13,7 ± 0,13 mil millones de años y que las primeras estrellas se formaron cientos de millones de años después del Big Bang. En este trabajo, se argumenta que podemos dividir la historia cosmológica en cuatro edades, desde el Big Bang a la vida inteligente.
Observation of large scale precursor correlations between cosmic rays and ear...Sérgio Sacani
The search for correlations between secondary cosmic ray detection rates and seismic
effects has long been a subject of investigation motivated by the hope of identifying a new
precursor type that could feed a global early warning system against earthquakes. Here we show
for the first time that the average variation of the cosmic ray detection rates correlates with the
global seismic activity to be observed with a time lag of approximately two weeks, and that the
significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a
shift in phase of around three years, exceeding 6 𝜎 at local maxima. The precursor characteristics
of the observed correlations point to a pioneer perspective of an early warning system against
earthquakes.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Artigo descreve como os cientistas utilizaram o Telescópio Espacial Hubble para descobrir a estratosfera num exoplaneta classificado como um Júpiter quente. Descoberta essa que pode ajudar a descobrir como os exoplanetas se formam e qual a composição de suas atmosferas.
1) Gale Crater is a potential landing site for the Mars Science Laboratory rover. It contains a large mound of layered sediment in the crater's center over 5 km thick.
2) Previous studies have proposed various origins for the mound materials, including lacustrine, aeolian, pyroclastic, and spring deposits. However, the exact origin remains uncertain.
3) This study uses high-resolution imagery and spectral data to characterize the geomorphology and stratigraphy of the mound and crater in order to better understand the depositional environment(s) and evaluate hypotheses for the mound's origin.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
This document describes a model of crater formation on the Moon and terrestrial planets based on the current understanding of the impactor population in the inner Solar System. The model calculates impact rates spatially across planetary surfaces to account for nonuniform cratering. It finds that the lunar cratering rate varies with latitude and longitude, being about 25% lower in some regions and higher in others. The model reconciles measured lunar crater size-frequency distributions with observations of near-Earth objects, assuming the presence of a porous lunar megaregolith affects the size of small craters. It provides revised estimates of the ages of some lunar and planetary geological features based on crater counts and the derived crater chronology.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
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High-altitude nuclear explosions in the late 1950s and early 1960s produced unintended effects on space weather through the creation of artificial radiation belts and electromagnetic pulses (EMPs). These explosions generated radiation that damaged satellites and could potentially damage modern electronics over large areas. Other anthropogenic impacts on space weather discussed include chemical releases, ionosphere heating experiments, and interactions between VLF radio waves and radiation belts. While the effects of human activities are difficult to separate from natural space weather drivers, modern technology has increased humanity's influence on the near-Earth space environment.
The hazardous km-sized NEOs of the next thousands of yearsSérgio Sacani
This document discusses methods for assessing the long-term impact risk of km-sized near-Earth objects (NEOs) over thousands of years. It analyzes the evolution of the Minimum Orbit Intersection Distance (MOID) between NEOs and Earth to identify objects that remain in close proximity for extended periods. It then estimates the probability of a deep Earth encounter during these low-MOID periods based on the growth of orbital uncertainties over time. This allows the authors to rank km-sized NEOs by their long-term impact hazard and identify targets that warrant further observation and analysis.
This document discusses how geomagnetic storms can affect marine archaeological surveys by introducing noise and masking spatial variations in Earth's magnetic field that are used to identify archaeological anomalies. The study analyzed 34 geomagnetic storms and found that their sudden onset signatures were indistinguishable from archaeological anomalies. Based on this, it is estimated that 89.7-100% of strong geomagnetic storms will generate signatures that could be misinterpreted as archaeological sites. The document recommends improved data collection and processing methods to better account for geomagnetic storms and improve precision in identifying archaeological resources.
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.
The Expansion of the X-Ray Nebula Around η CarSérgio Sacani
1. The author analyzes over 20 years of Chandra X-ray images to measure for the first time the expansion of the X-ray nebula around η Carinae.
2. A combined Chandra image reveals a faint, nearly uniform elliptical shell surrounding the X-ray bright ring, with a similar orientation and shape as the Homunculus nebula but about 3 times larger.
3. The author measures proper motions of brighter regions associated with the X-ray emitting ring, such as the S-ridge and W-arc. Motions are consistent with optical studies of ejecta from the 1840s Great Eruption.
In Situ Geophysical Exploration by Humans in Mars Analog EnvironmentsBrian Shiro
Presented on May 13, 2010 at the University of North Dakota's 997 symposium. Summarizes the research projects I carried out on two analog Mars missions in 2009 and 2010.
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU...Sérgio Sacani
This document summarizes observations from the Hubble Space Telescope of the young hot Neptune exoplanet AU Mic b, which orbits the nearby M dwarf star AU Mic. The observations aimed to detect atmospheric escape of neutral hydrogen through absorption in the stellar Lyman-alpha emission line. Two visits were obtained, one in 2020 and one in 2021, corresponding to transits of the planet. A stellar flare was observed and removed from the first visit data. In the second visit, absorption was detected in the blue wing of the Lyman-alpha line 2.5 hours before the white light transit, indicating the presence of high-velocity neutral hydrogen escaping the planet's atmosphere and traveling toward the observer. Estimates place the column density of this material
1) New data from the GRAIL gravity mission and LOLA altimetry is helping to determine the structure of the lunar highlands crust.
2) Preliminary GRAIL gravity models show noise levels are lower than expected, indicating signals exist at even shorter wavelengths than planned.
3) Combined analysis of gravity and topography data can provide insights into crustal thickness, elastic properties of the lithosphere, and the thermal state during and after bombardment.
Transit photometry has been the most successful exoplanet discovery method to date. It works by detecting the dimming of a star's light as a planet passes in front of it. From the transit light curve, properties of the planet like its radius and orbital parameters can be derived. However, transits have a low probability of being aligned with our line of sight. False positives from eclipsing binaries can also mimic transits, so follow-up observations are needed to confirm planetary discoveries. Past and current transit surveys have found over a hundred planets, and future surveys aim to detect smaller planets orbiting brighter stars.
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
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
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
La historia de la vida en la Tierra y en otras plataformas planetarios potenciales portadoras de vida están profundamente ligadas a la historia del Universo. Puesto que la vida, tal como la conocemos, se basa en elementos químicos forjados en estrellas pesadas moribundas, el Universo tiene que ser lo suficientemente antiguo para que las estrellas se formaran y evolucionaran. La teoría cosmológica actual indica que el Universo es de 13,7 ± 0,13 mil millones de años y que las primeras estrellas se formaron cientos de millones de años después del Big Bang. En este trabajo, se argumenta que podemos dividir la historia cosmológica en cuatro edades, desde el Big Bang a la vida inteligente.
Observation of large scale precursor correlations between cosmic rays and ear...Sérgio Sacani
The search for correlations between secondary cosmic ray detection rates and seismic
effects has long been a subject of investigation motivated by the hope of identifying a new
precursor type that could feed a global early warning system against earthquakes. Here we show
for the first time that the average variation of the cosmic ray detection rates correlates with the
global seismic activity to be observed with a time lag of approximately two weeks, and that the
significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a
shift in phase of around three years, exceeding 6 𝜎 at local maxima. The precursor characteristics
of the observed correlations point to a pioneer perspective of an early warning system against
earthquakes.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Artigo descreve como os cientistas utilizaram o Telescópio Espacial Hubble para descobrir a estratosfera num exoplaneta classificado como um Júpiter quente. Descoberta essa que pode ajudar a descobrir como os exoplanetas se formam e qual a composição de suas atmosferas.
1) Gale Crater is a potential landing site for the Mars Science Laboratory rover. It contains a large mound of layered sediment in the crater's center over 5 km thick.
2) Previous studies have proposed various origins for the mound materials, including lacustrine, aeolian, pyroclastic, and spring deposits. However, the exact origin remains uncertain.
3) This study uses high-resolution imagery and spectral data to characterize the geomorphology and stratigraphy of the mound and crater in order to better understand the depositional environment(s) and evaluate hypotheses for the mound's origin.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
This document describes a model of crater formation on the Moon and terrestrial planets based on the current understanding of the impactor population in the inner Solar System. The model calculates impact rates spatially across planetary surfaces to account for nonuniform cratering. It finds that the lunar cratering rate varies with latitude and longitude, being about 25% lower in some regions and higher in others. The model reconciles measured lunar crater size-frequency distributions with observations of near-Earth objects, assuming the presence of a porous lunar megaregolith affects the size of small craters. It provides revised estimates of the ages of some lunar and planetary geological features based on crater counts and the derived crater chronology.
Similar to Exploring Martian Magnetic Fields with a Helicopter (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
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.
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.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
Nucleophilic Addition of carbonyl compounds.pptxSSR02
Nucleophilic addition is the most important reaction of carbonyls. Not just aldehydes and ketones, but also carboxylic acid derivatives in general.
Carbonyls undergo addition reactions with a large range of nucleophiles.
Comparing the relative basicity of the nucleophile and the product is extremely helpful in determining how reversible the addition reaction is. Reactions with Grignards and hydrides are irreversible. Reactions with weak bases like halides and carboxylates generally don’t happen.
Electronic effects (inductive effects, electron donation) have a large impact on reactivity.
Large groups adjacent to the carbonyl will slow the rate of reaction.
Neutral nucleophiles can also add to carbonyls, although their additions are generally slower and more reversible. Acid catalysis is sometimes employed to increase the rate of addition.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
ANAMOLOUS SECONDARY GROWTH IN DICOT ROOTS.pptxRASHMI M G
Abnormal or anomalous secondary growth in plants. It defines secondary growth as an increase in plant girth due to vascular cambium or cork cambium. Anomalous secondary growth does not follow the normal pattern of a single vascular cambium producing xylem internally and phloem externally.
2. Table 1
Scientific Traceability of Magnetic Field Measurements; Scientific Questions Are Related to (M) Magnetization, (D) Dynamo and (HE) Human Exploration
MEPAG Goal and
Objective Scientific Questions Observable Quantities Possible Issues Additional Instrumentation and Mitigation Strategies
MEPAG Goal III:
understand the
origin and evol-
ution of Mars as
a geological
system
Crustal composition:
(M1) What are the
carriers of
magnetization?
• Magnetized surface fea-
ture
• General geochemical
analysis of the miner-
alogy of the crust (no
matter if magnetized)
Surficial mineralogy
not necessarily
representative; bur-
ied layers cannot be
accessed
Spectrometers for analysis of elemental and mineralogical composition
Objective A:
document the
geologic record
preserved in the
crust and inves-
tigate the pro-
cesses that have
created and
modified that
record
(M2) Magnetization
strength: what
gives rise to strong
magnetization? Is it
a thick magnetized
layer, distinct
mineralogy, or a
combination
thereof?
• Magnetized feature of
known volume such as
pebble/clast.
• Magnetized layer for
which depth/volume
can be approximated,
e.g., magnetic field
observations at varying
survey altitudes.
Pebble/clast not mag-
netized; volume of
features not easy to
evaluate
• Imagery to identify pebbles/clasts or layering and approximate volume.
• Gravimeter to approximate density/composition of magnetized feature. Joint inversion can
potentially aid in 3D modeling of underlying magnetized volume.
• Spectrometers to get insight on composition/magnetization carrier.
Crustal creation and
modification:
(M3) What are the
dominant magneti-
zation acquisition
mechanisms? How
do they vary?
Measure magnetic field in
different geological
settings, e.g., volcanic
versus aqueous
alteration
Source of magnetiza-
tion not easily iden-
tifiable, e.g.,
magnetization origi-
nates at depth (i.e.,
hydrothermal versus
volcanic intrusion)
• Mineralogy and imagery to identify origin of material, i.e, surficial volcanic versus altered
rock.
• Gravimeters can provide information on subsurface density and thus carry information on
rock type and alteration state.
(M4) What are the
typical length
scales of
magnetization?
Magnetic field changes
along the flight path if
possible at different
altitudes and in com-
parison with previous
landed/orbital
measurements
Possible lack of chan-
ges along path;
especially if in-flight
not an option, ROI
measurements too
limited?
Multiple orthogonal flights over a given region
Objective B:
determine the
structure, com-
position, and
dynamics of the
interior and how
it has evolved
Global planetary
evolution:
(D1) When did the
dynamo operate?
• Magnetized dateable
feature at surface.
• Clear demagnetization
signature indicating that
surface layer is magne-
tized.
• Age constraints on
magnetized and unmag-
netized units.
No surface
magnetization
Gravimeter: identify the magnetized source body by identifying units of different density and
thus potential to infer composition
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3. Table 1
(Continued)
MEPAG Goal and
Objective Scientific Questions Observable Quantities Possible Issues Additional Instrumentation and Mitigation Strategies
(D2) Dynamo char-
acteristics: did the
polarity change?
How strong was the
dynamo field?
What are the driv-
ing mechanisms?
• Identify magnetized
dateable layers.
• Evaluate magnetization
for observable volume
to infer dynamo
strength.
No observable layering;
no surface
magnetization
Imagery to identify dateable surface features to be linked to the presence or absence of
magnetization associated with the feature
MEPAG Goal IV:
prepare for
human explora-
tion
Objective A:
obtain knowl-
edge of Mars
sufficient to
design and
implement
human landing
at the designated
human landing
site with accep-
table cost, risk,
and
performance.
(HE1) How deep in
the crust are iron-
bearing mineral
resources?
(HE2) What is the
radiation environ-
ment on the Mar-
tian surface?
Low-altitude vector
magnetic field survey
If in-flight not an
option, ROI mea-
surements too
limited?
• Gravimeter: identify the magnetized source body by identifying units of different density
and enable joint inversions.
• Measurements at multiple altitudes to better constrain the source region.
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4. Here we summarize key questions in Mars magnetism linked
to broader questions about planetary systems as defined by
MEPAG and point out key observables that would allow these
questions to be addressed using low-altitude measurement
platforms (Table 1). We refer to Mitteholz & Johnson (2022)
for a more detailed discussion of magnetic data sets, what we
have learned from them, and remaining key knowledge gaps.
The dynamo (D1 and D2 in Table 1) provides important
information on early Mars evolution for which the dynamo
timing, driving mechanisms, and possible changes in polarity
and strength are key constraints. MEPAG Goal III.B clearly
motivates investigation of the evolution of the ancient Martian
dynamo and the manner and timing of its demise. Clues to this
lie in the crustal material that was magnetized by the dynamo
magnetic field (M1–M4 in Table 1). Further, although we know
that the Martian crust is strongly magnetized in some places,
we do not know the origin of this magnetization. There is a
general understanding of possible magnetic carriers from
meteorites and consideration of the Martian redox state
(Dunlop & Arkani-Hamed 2005; Rochette et al. 2005; Tikoo
& Evans 2022), but we do not know the source mineralogy of
the anomalies (M1 and M2) or the process(es) that magnetized
the rocks (M3). MEPAG Goal III.A points out the importance
of investigating the geological record preserved in the crust and
magnetization as an important characteristic that contains
information on the time the crust formed, as well as how it was
modified over time and in response to heat, water, and/or
shock. Further, the connection to ancient climate as highlighted
in MEPAG Goal II.C is twofold. First, the shutdown of the
dynamo and loss of the global magnetic field would have
fundamentally altered the rate and manner of atmospheric
escape (Ramstad & Barabash 2021), but although a connection
has been hypothesized, the degree of connection between the
dynamo and the Martian climate is unclear. However, to
address this question, timing constraints as discussed in D1 are
essential. Second, magnetization acquisition processes invol-
ving water as discussed in M3 would (if important) be
interconnected with an ancient hydrosphere. This MEPAG goal
is not explicitly listed in Table 1 due to its interconnections
with previous questions. Lastly, in preparation for future
human exploration (MEPAG Goal IV), geophysical character-
ization of the subsurface and possible identification of iron-
bearing material resources are of importance for future human
settlement efforts (HE1). So is a good understanding of local-
scale (kilometers to tens of kilometers) crustal magnetic fields,
which might provide protection from radiation (HE2). The
degree of this protection has been shown to strongly depend on
crustal field geometry (Emoto et al. 2018). With a lack of
understanding of the strength, distribution, and geometry of
surface magnetic fields, this question cannot be sufficiently
addressed.
Existing magnetic field data sets, as well as magnetic field
and magnetization models developed from them, provide
context for regional studies that can capture information at
spatial scales >100 km. However, investigating smaller-scale
magnetic fields on Mars can provide information that simply
cannot be gleaned from orbit. A well-known terrestrial analog
is the pattern of alternating linear marine magnetic anomalies
with a horizontal extent of ∼20 km (“magnetic stripes”)
parallel to mid-oceanic ridges that provided key supporting
evidence for both plate tectonics (Vine & Matthews 1963) and
global magnetic field reversals. These signals are revealed in
shipboard and aircraft survey data but are not detectable from
satellite orbit altitudes (Ravat 2011).
Although existing magnetic field data have provided
invaluable information on the Martian crustal magnetic field
(and more), each data set has distinct and serious limitations.
Satellite data provide a global picture but can only resolve scale
lengths comparable to orbital altitudes; for Mars, this is
typically 100–200 km. Lander measurements such as those
provided by InSight give only a single-point measurement of
the crustal magnetic field. A single-location measurement may
be explained by a large number of magnetization models,
requiring further constraints on the volume and location of the
magnetized source rock, to constrain the possible parameter
space (Johnson et al. 2020; Knapmeyer-Endrun et al. 2021;
Wieczorek et al. 2022). Rover observations, such as the data
from Zhurong, cover limited distances (hundreds of meters to
tens of kilometers), are surface observations (no vertical
distribution of measurements), and can only be obtained in
terrain that is accessible to rovers, i.e., less than ∼25° slopes. A
helicopter is the ideal platform to overcome such limitations; it
enables comprehensive aerial surveys at low altitudes that can
detect unexplored signals, bridging the gap between surface
and orbital observations. In addition, it can traverse any terrain,
including the steep walls of valleys, canyons, and craters, in
addition to dune and boulder fields and other hazardous terrain.
As a first step toward realizing a magnetic helicopter
mission, we need to consider the types of data sets and
modeling techniques that we might be able to exploit. Magnetic
field modeling on Mars has mostly been based on orbital vector
magnetic field data so far, and different modeling approaches
have been used to build local and global models of the
magnetic field (e.g., Figure 1). One common class of models
are parameterized by spherical harmonics that are fit to the data
and produce a model of the magnetic field (e.g., Cain 2003;
Morschhauser et al. 2014). Others have used equivalent source
dipole models (Mayhew 1979) for which the magnetic
moments of dipoles in a single subsurface layer are fit to the
satellite observations (e.g., Purucker et al. 2000; Mittelholz
et al. 2018; Langlais et al. 2019). While these models solve for
possible magnetization distributions from which the magnetic
field can be predicted, they suffer from nonuniqueness; i.e., a
very wide range of crustal magnetization distributions can
result in the same pattern of fields measured from orbit. In other
words, these models cannot resolve 3D structure given their
large receiver–source distances.
Figure 1. Magnetic field amplitude, |B|, from a satellite data-based model,
downward continued to the surface (Langlais et al. 2019). The star represents
the InSight landing site, with the model surface prediction of ∼300 nT vs. the
actual ∼2000 nT measured by InSight’s magnetometer. The circles outline the
big impact basins Hellas, Utopia, Argyre, and Isidis for context.
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5. Further, different models use different inversion approaches.
For example, the use of different norms largely influences how
localized anomalies appear in a given model. The most classic
models use least-squares or L2 norms and create smooth
models (e.g., Mittelholz et al. 2018; Langlais et al. 2019 ). An
iterative approach of different model norms was applied by
Morschhauser et al. (2014) aiming for a better representation of
localized anomalies compared to L2 models. Others have
created sparse models using an L1 norm, and such models
favor compact anomalies (Moore & Bloxham 2017). While
these approaches provide different magnetic field models, they
all are consistent with the data. Hence, the choice of model
norm guides the nature of the recovered model.
Potential field data do not intrinsically have depth resolution,
and the nonuniqueness of different models is an inherent
property of such fields. However, data collected at lower and
variable altitudes and with denser coverage would enable high
spatial resolution; thus, more targeted questions could be
addressed. Methods for inverting such data sets to obtain 3D
models are advanced in terrestrial geophysics, which will aid us
in the interpretation of such models. Thus, a helicopter
magnetic field data set will allow the characterization of crustal
magnetization in unprecedented detail and the construction of
significantly higher-resolution models, both horizontally and
vertically. That is, there is no substitute for low-altitude in situ
measurements of crustal magnetic fields.
In this paper, we discuss example crustal magnetization
scenarios and survey designs for future aerial surveys with a
focus on helicopters. Many aspects explored in this paper are
applicable to other low-altitude platforms, such as balloons
(Hall et al. 2007) or airplanes (Braun et al. 2006). We first
discuss the magnetic field we might expect to measure using a
helicopter-borne magnetometer and include magnetic field
contributions from crustal magnetization and magnetic noise.
We explore three geological scenarios and different survey
geometries and investigate how well magnetized structures can
be recovered in models. In the light of helicopter data sets that
might comprise sparse data compared to terrestrial regional
surveys, we examine a range of inversion methodologies and
discuss ways in which different inversion approaches can
identify different types of structures for our hypothetical
scenarios. Finally, based on our modeling efforts, we offer
recommendations for a future helicopter mission to Mars.
2. A Helicopter Mission on Mars
2.1. Helicopter Mission Concepts
Future Mars helicopter missions include Sample Recovery
Helicopter–like vehicles (Mier-Hicks et al. 2023), capable of
carrying up to 1 kg of payload tens to hundreds of kilometers
for a standard mission duration (∼1 Mars year), or larger Mars
Science Helicopter concepts that are capable of carrying up to
5 kg of payload hundreds of kilometers (Bapst et al. 2021).
Both would enable low-altitude coverage (up to several
hundred meters) and offer the possibility of surveying the
magnetic field of Martian regions in an unprecedented manner.
Because magnetometers are lightweight and consume little
power, and they can take advantage of low-altitude aerial
mapping, we will now focus on discussing these highly
relevant mission strategies.
A possible survey strategy includes several regions of
interest (ROIs) that can be defined in advance using results
from orbital data depending on the overall mission goals. The
helicopter can perform in-depth analysis of those ROIs using its
full instrument suite in conjunction with local/regional context
from flight traverses (Figure 2(a)).
Here we explore three magnetic field data set scenarios. In
the first, we construct gridded data sets that provide evenly
distributed measurements. The data sets and resulting inver-
sions can be compared with those from more realistic survey
strategies: one for which data are only collected on the ground
and when the helicopter is not moving and one in which in-
flight measurements are also possible. The latter option requires
a more advanced magnetic cleanliness program (discussed in
Section 5) but can take full advantage of the complete
flight path.
2.2. Magnetic Field Contributions
Generally, contributions to the overall measured magnetic
field are of spacecraft and Mars external and internal origin,
i.e., sources above and below the planetary surface, respec-
tively. We assume that helicopter-generated fields can be
characterized and subtracted, and only naturally occurring
fields are discussed. For a typical helicopter survey, mapping of
the crustal magnetic field would be the primary mission
objective, but regardless of whether external fields are of
interest by themselves, separating internal and external
contributions is required.
The internal magnetic field depends on the location of the
measurement and, due to the absence of a Martian dynamo
field, results solely from crustal magnetization. Amplitudes of
the crustal magnetic field vary greatly, and satellite data-based
surface predictions range from zero to 12,000 nT with an
average and median of 450 and 200 nT, respectively (Figure 1;
Langlais et al. 2019). However, those predictions are based on
orbital data that are insensitive to small-scale (<∼100 km)
magnetization. At the InSight landing site, the predicted
magnetic field amplitude (Smrekar et al. 2018) was approxi-
mately 10% of the observed ∼2000 nT (Johnson et al. 2020).
The strength of the predicted field at InSight is close to the
global median value, and we might thus expect to find many
similar and even stronger fields at the Martian surface.
However, in less magnetized regions, such as in the northern
hemisphere, crustal fields at the surface could be close to zero.
Figure 2. Helicopter scenarios. Blue shading represents measurements taken in
flight. (a) Representation of different sampling scenarios between ROIs. Panels
(b)–(d) are the scenarios modeled in Section 3 and represent a magnetized
crater, differently magnetized layers, and a magnetized dike intrusion; panel (e)
represents surveying of individual pebbles.
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6. This is, for example, the case for the Zhurong measurement
sites (Du et al. 2023).
External magnetic fields at the surface can be of periodic
nature, e.g., due to ionospheric currents (Lillis et al. 2019;
Johnson et al. 2020; Mittelholz et al. 2020b), the interplanetary
magnetic field (Langlais et al. 2017; Luo et al. 2022; Mittelholz
et al. 2023), or transients, such as space weather (Mittelholz
et al. 2021b) or dust movement (Thorne et al. 2022). InSight
provides surface observations over a prolonged time frame, and
although external field phenomena are summarized elsewhere
(Mittelholz et al. 2023), we list them in Table 2 to assess how
large their contributions might be and whether they would
affect crustal magnetic field measurements. Note that a
different crustal magnetic field environment (that is, in a
different location) would affect ionospheric currents and the
resulting magnetic fields (Lillis et al. 2019).
Short-period fluctuations are observed at dusk/dawn and
around midnight. Even if measurements were taken during
those times, the fluctuations are on the order of only a few
nanoteslas (Chi et al. 2019; Johnson et al. 2020). Daily
fluctuations due to ionospheric currents, however, could lead to
signals of tens to hundreds of nanoteslas depending on the
strength of the background magnetic field and season (Lillis
et al. 2019; Mittelholz et al. 2023). For InSight, daily
fluctuations have been found to vary with season and dust
content, and individual days can vary by tens of nanoteslas
(Mittelholz et al. 2020b). Longer-period fluctuations associated
with the interplanetary magnetic field are small at the InSight
landing site, and their effect is likely negligible (Mittelholz
et al. 2023). For a helicopter survey, identification and
characterization of transient sources are unlikely to present a
challenge because their amplitude is either too small, e.g., dust
devils (Thorne et al. 2022), or, for ionospheric and magneto-
spheric currents, they can be either recognized by their time/
diurnal profile or avoided/ignored during times of space
weather (Mittelholz et al. 2021b).
The effect due to spatially and temporally varying magnetic
field fluctuations depends on whether data are collected in
flight or while landed at ROIs only. For landed measurements,
i.e., measurements taken when the helicopter or rotor system is
not moving, contributions to the measured magnetic field
consist of the crustal magnetic field at that specific landing site
and time-varying magnetic fields over a longer time frame
(Table 2). Especially if the helicopter collects data during the
nighttime, the time-varying external field contributions are
minimal and can easily be identified and subtracted from the
crustal contribution. For in-flight measurements, subtracting
external fields would be more challenging, as the internal field
also varies as the helicopter flies across varying crustal
magnetic anomalies. Generally, to separate internal and
external fields we recommend repeat measurements covering
ROIs several times and at magnetically quiet periods, and
vertical flights at several locations across the region.
Finally, crustal contributions are expected to outweigh
external field contributions at many locations. Landed
measurements enable individual robust crustal field measure-
ments because time-varying magnetic fields can be readily
identified, especially during magnetically quiet nights. Track-
ing of diurnal fluctuations while on the ground could then
inform on spatially varying crustal fields versus external
variations for in-flight measurements. Additional data collected
during the traverse would ensure dense coverage of flight paths
between landed measurements and enable crustal magnetic
field characterization of unprecedented resolution.
2.3. Helicopter Magnetic Field Surveys
One advantage of airborne surveys is the traversability in any
terrain, such as boulder fields and along steep walls. We
present a range of geological settings that one could encounter
on Mars and for which magnetic signatures might be expected.
First, magnetization associated with craters (or the lack of
magnetization) has been used previously to constrain the timing
of the dynamo (Lillis et al. 2013; Vervelidou et al. 2017;
Mittelholz et al. 2020a). This addresses questions D1 and D2 in
Table 1. (De)magnetization signatures associated with crater
interiors arise due to the effect of shock and heating during an
impact (Mohit & Arkani-Hamed 2004; Gattacceca et al. 2008).
Excavation of magnetized material can also have an effect
(Mittelholz et al. 2020a; Ojha & Mittelholz 2023), and this has
been used to constrain the dynamo to 3.7 Ga. Craters on Mars
are ubiquitous (Robbins et al. 2013), and any landing site
would likely offer the opportunity to traverse impact craters
and ejecta. As such, in this scenario, we can test if a dynamo
operated at the time of the impact. A test of magnetizations of
features (not necessarily craters) of several different ages is
necessary to construct a timeline of the Martian dynamo and
help constrain the evolution of the interior state of Mars, i.e.,
changing from sustaining a dynamo to being unable to do so.
Hence, this is a highly relevant scenario for any future mission
with a magnetic focus.
Table 2
Time-varying Magnetic Field Contributions Measured on the Surface by InSight
Phenomenon Magnetic Signal Notes
Daily: ionospheric currents Typical peak amplitudes up to 40 nT Magnetic fields driven by ionospheric currents are
minimal during the nighttime and peak in the
early to mid-morning
Short-period waves or pulsations: magnetic fields
driven by interaction of magnetosphere with
solar wind
Typical peak amplitudes up to a few nT with periods
of hundreds to thousands of seconds
Typically observed at dust/dawn and around mid-
night on horizontal components
Transient sources: solar events Increased peak diurnal amplitudes in all components;
nighttime fluctuations (periods ∼20–30 minutes)
up to ∼10 nT
Solar events can be predicted and tracked but have
an effect for multiple days
Transient sources: dust movement Small-amplitude signals <0.5 nT for ∼10 seconds The frequency of such events would likely depend
on dust availability at the landing site.
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7. In a second scenario, we investigate the magnetization
signature of a dike intrusion. Generally, magmatic activity
throughout Martian history is evident (Tanaka et al. 2014), and
dikes have been mapped in volcanically active areas such as
Tharsis (Brustel et al. 2017; Pieterek et al. 2022) or indirectly
inferred from rift structures or seismic data (Nimmo &
Stevenson 2000; Stähler et al. 2022). Magnetization associated
with dateable volcanic features can address volcanic and
dynamo evolution (Johnson & Phillips 2005; Lillis et al. 2006;
Mittelholz et al. 2020a). Again, this is linked to questions D1
and D2, but especially in comparison with the above examples,
it allows one to characterize magnetization that is known to be
linked to thermal effects as opposed to a site in which one
observed clear signs of shock or alteration (questions M1–M4).
For example, the analysis of the magnetic field of a dike could
reveal a demagnetization signature for a young intrusion in a
magnetized layer or a magnetization signature if the intrusion
and the surrounding layer were emplaced while a dynamo was
active. Furthermore, ferrous mineralogies of the dike could
enhance the magnetization compared to the background.
Moreover, this particular example is defined to address
resolvability, i.e., how well very small features can be resolved,
irrespective of the science question asked.
Lastly, we consider layering that could be found in a valley
or graben structure (Nedell et al. 1987; Le Deit et al. 2010).
This would offer ideal conditions to traverse multiple layers of
different ages to establish a magnetic timeline and address the
question of dynamo activity and possible polarity changes over
the range of emplacement ages represented in the set of strata
(D2). At least one polarity change has been hypothesized based
on orbital data and the meteorite ALH84001 (Thomas et al.
2018; Steele et al. 2023); testing the characteristics of a
dynamo over time would provide unprecedented information
on interior evolution. Stacked layers of different material and
possibly different origins would further allow one to address all
questions labeled M in Table 1. From a more technical
perspective, this scenario also allows intuition to be gained on
expected magnetic signals across at least two distinct blocks of
magnetization.
3. Modeling Approach
3.1. Background
In preparation for future missions, in this study, we model
the proposed scenarios and perform inversions to investigate
the degree to which we can recover magnetized structure. We
use the open-source SimPEG package in Python (Cockett et al.
2015), and an example code is available online. First, we
simulate magnetic field data collected by a helicopter above a
given magnetization model; this is the forward problem. From
Gauss’s law, the relation between magnetization per unit
volume M in Am−1
and magnetic field B in teslas is
( ) · ( )
ò
m
p
=
B M
r
r
dV
4
1
, 1
V
0
where r is the radial distance between the measurement point
and the magnetic source of volume V, and μ0 is the magnetic
permeability of free space. Using simulated data, d, we then
aim to recover our model, m, by solving an inverse problem.
First, we define the parameters we aim to estimate by solving
the inverse problem. We use a voxel model of the subsurface,
where each cell has a vector magnetization that we seek to
estimate (Lelièvre & Oldenburg 2009). The inverse problem is
nonunique and underdetermined; i.e., there are infinite possible
solutions. Therefore, one needs to incorporate additional
constraints. Traditionally, the inverse problem can be for-
mulated as an optimization problem (Tikhonov et al. 1995) in
which one can impose regularization and minimize an objective
function that contains a data misfit term, Φd, and a model
regularization term, Φm. The trade-off parameter β controls the
relative importance between the two competing terms, and *
Fd
represents an acceptable target misfit:
( ) ( )
*
b
F = F + F F F
m
min subject to . 2
d m d d
The first term, Φd, describes the misfit between observed,
dobs, and predicted, dpred, data,
( )
( )
å s
F =
-
=
d d
, 3
d
i
N
i i
i
1
pred obs
normalized by estimated uncertainties σ for each data point i.
Assuming that the noise and error on the data are random, the
expected target misfit *
Fd = N, where N is the number of data.
The second term penalizes differences between the model
and a reference model and can be made up of several functions
that control the magnitude and roughness of the model,
∣ ( )∣ ( )
ò
å
F =
=
w f m dV, 4
m
r s x y z V
r r
p
, , ,
r
where fr consists of one or more of fs = m, fx = dm/dx,
fy = dm/dy, and fz = dm/dz, describing the smallness and
roughness in all orthogonal directions. The weighting term wr
adjusts the importance of the regularization terms. Lastly, we
use the general lp norm, which can be independently adapted
for the different regularization functions with 0 „pr „2.
In order to minimize Equation (2), we discretize our model
onto a tensor mesh and find a solution such that the gradient of
the objective function ∇mΦ(m) = 0. The trade-off parameter β
is decreased until a defined threshold tolerance is reached or
after a given maximum number of iterations. The inexact
Gauss–Newton algorithm is used to calculate appropriate
model updates; for more details on the inversion, we refer
the reader to Fournier & Oldenburg (2019).
3.2. Survey Geometry and Model Setup
We simulate three different survey geometries with a
decreasing number of measurements for each of the scenarios
described in Section 2.1. First, we construct a regular tensor
mesh across the ROI and simulate the data that would result
from the magnetization model if the data were collected on an
idealized grid (Figures 4(a) and (b)). For example, for the crater
scenario, the survey includes 15 × 15 data points across a
600 × 600 m area, resulting in 225 data points (Figures 4(b)
and (f)). The next survey geometry simulates the flight path of a
helicopter; the helicopter lifts off the ground up to an altitude of
10 m at the center point of each track before it lands. We
simulate three tracks with 30 data points on each (Figures 4(c)
and (g)). Note that changing altitude contributes to the
magnetic field observation; i.e., the magnetic field signal is
decreased at times when the helicopter is further away from the
surface and the source of magnetization. With an approximate
helicopter speed of 10 m s−1
, the 30 data points across 10 m
equate to a sampling rate of 30 samples s–1
. Lastly, we explore
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8. the scenario in which the helicopter only collects data on the
ground (i.e., when it is not flying). Six measurements at
discrete locations are collected in this survey (Figures 4(d) and
(h)). For all models, we assume background noise with a
standard deviation of 0.1 nT, but we vary this parameter in
Section 5.1.
3.3. Modeling Strategy
We propose a modeling strategy in which different inversion
techniques are applied consecutively to achieve confidence in
the recovered magnetization and inferred geological models
(Figure 3). While some techniques rely on no or minimal
a priori information, we also show examples of how a priori
information, i.e., information from other data sets, particularly
imagery, can be incorporated into the inversion. As sketched in
Figure 3, after data acquisition, we initially generate a smooth
L2 inversion for a first estimate of the distribution of
magnetization and its possible relation to observable surface
structures (Section 3.3.1). Next, we aim for a model that will
highlight contrasts and produce compact structure in a sparse
inversion (Section 3.3.2). We then incorporate knowledge of
geological structure or layering in the inversion (Sections 3.3.3,
3.3.4, and 3.3.5). Different techniques are briefly described
below and later applied to the different scenarios to showcase
the range of different inversion strategies.
3.3.1. Smooth Inversions
Traditionally, an L2 norm is used for the regularization term
(Equation (4)); i.e., pr is set to 2. The L2 inversion results
provide a smooth picture of the magnetization, which, in the
case of structure that extends at depth or does not have clearly
defined edges, can provide an adequate model. With no prior
information, we consider this a good first approximation and
perform such an inversion for each scenario. However, L2
modeling can smear out compact features and be too smooth to
be geologically interpretable.
3.3.2. Sparse-norm Inversions
We also explore more compact solutions with 0 „ pr < 2.
For small ps, the inversion favors compact anomalies with large
physical property contrasts, while reducing the px,y,z values
generates flat anomalies with sharp edges along the Cartesian
directions. These approaches do not require prior information.
However, in both types of inversion, regularization can be
tuned to, for example, emphasize compactness in particular
directions because different regularization terms have their
individual weighting terms. More details on this inversion and
a comparison to the smooth L2 inversion as implemented in
SimPEG are provided in Fournier et al. (2020).
3.3.3. Single Layer
Crustal magnetic field models on Mars have so far used a
single layer of dipoles, not attempting to resolve 3D structure
with low-resolution satellite data, thus providing an integrated
picture of the subsurface (e.g., Vervelidou et al. 2017;
Mittelholz et al. 2018; Langlais et al. 2019). This simplified
approach can be a useful tool in identifying the horizontal
extent of magnetization in the subsurface without attempting to
resolve 3D structure, i.e., thickness and lateral variations of
magnetization at depth. Because this strategy greatly reduces
the model space, it can be useful to quickly gain insight into
any relationships between surface geology and magnetization.
We adapt this strategy for the intrusion scenario and implement
a 1 voxel vertical layer of elongated cuboids. While one can
perform smooth or sparse model inversions, we only show
results for the smooth solution.
3.3.4. Parametric Model
For a simple and well-constrained geological structure,
additional information may allow parameterization of the
model with only a few variables while keeping the surrounding
structure parameterized with voxels. This greatly reduces the
number of model parameters and can convert the under-
determined problem into an overdetermined problem, for which
regularization is not necessary. Images outlining, e.g., a dike or
crater, i.e., prior information on the magnetization geometry,
are applications in which this approach can be useful. In our
example, we will represent the crater by a half-sphere and can
describe it by its center location in 3D [x, y, z]; its radius, r; and
its magnetization vector [mx, my, mz]. Note that this approach
may be combined with, e.g., a smooth inversion and used as a
hybrid approach when only part of the subsurface is well
constrained (Herring et al. 2022).
3.3.5. Domain Mapping
Lastly, if distinct units are observed that might be uniformly
magnetized, it can be useful to apply a simple mapping
function and solve only for magnetization associated with the
identified units. Thus, the inverse model space is mapped onto
the physical properties space to use in the forward simulation
that now only depends on the specified number of properties as
opposed to the number of model cells. Layers can often be
identified a priori, and here we adapt the domain mapping
methodology for the layer scenario. Because we deal with three
different units (with a 3D magnetization), we now only solve
for 3 × 3 parameters. Other studies have used this technique to
reduce the model space from 3D to 2D or 1D, and explore
physical property distribution in progressively higher dimen-
sionality and complexity (Kang et al. 2015).
4. Results
In the following, we present the scenarios (Figure 2) using
the modeling strategies described above (Figure 3). Imposed
magnetizations for the different scenarios are chosen to be
Figure 3. Inversion strategy.
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9. reasonable estimates based on satellite-based models and
meteorites (e.g., Rochette et al. 2005; Langlais et al. 2019).
4.1. Scenario 1: Crater
The magnetized crater produces a magnetic field signature of
approximately 1 nT and is seen in all components. The initial
L2 inversion (Figures 4(f)–(h)) produces a relatively smeared-
out picture, particularly at depth. As a result, the magnetization
amplitude of the feature is underestimated, especially for the
landed case, for which there are insufficient data points to
determine the exact structure of the anomaly (Figure 4(h)). The
model does suggest the presence of a compact feature
motivating inversions using a sparse representation. The sparse
model (Figures 5(a)–(c)) captures the feature extent well,
especially for the dense survey coverage (Figure 5(a)). The
somewhat square outline of the crater feature is the result of
independent regularization of the three components in
combination with poor data coverage for the in-flight and
especially the landed cases (Figures 5(b) and (c)). Generally,
the amplitude of the feature can be recovered well. In both the
sparse and the smooth models, we observe low-amplitude
magnetization in the layers closest to the surface, which is
inconsistent with our model scenario (Figure 4(e)). This effect
arises because of the magnetization direction (45° and down-
ward) we have imposed on the model. As a next step, and
because we have identified a compact structure consistent with
the hypothesis that it is connected with the crater, we apply the
parameterized approach (Figures 5(d)–(f)). We approximate the
shape of the crater by a half-sphere and mcrater = [x, y, z, r, mx,
my, mz] = [0, 0, −40, 120, 7, 0, −7]. No matter the data
coverage, we obtain a model representation of the magnetized
crater that fits our model scenario well. Thus, even for limited
data, the representation is very good and clearly better than the
L2 or sparse representation.
4.2. Scenario 2: Dike
In the dike scenario, we cover a smaller area around a 15 m
diameter dike due to the small horizontal extent of the feature
(Figures 6(a) and (b)), and only a few data points in closest
proximity to the feature are affected (Figures 6(a)–(d)). The
initial L2 inversion for the dike again shows a smeared-out dike
feature that, even in absence of a priori information, is localized
(Figures 6(f)–(h)). Due to lacking depth sensitivity, the feature
is less well resolved vertically, and we cannot probe the dike’s
Figure 4. Scenario 1–Crater L2 inversion. (a) Different components and magnetic field amplitude of synthetic magnetic field data in the x–y plane from panel (e), a
magnetization model of a crater with a total magnetization amplitude of 10 A m−1
, where the color bar corresponds to the magnetization amplitude in the shown plane
(e.g., Mh = +
M M
x z
2 2
or +
M M
x y
2 2
), and the arrows represent the third vector component (e.g., My or Mz). This also applies to later figures that show arrows
(otherwise total amplitude is shown). (b)–(d) Different survey scenarios, (b) grid, (c) in-flight, and (d) landed, for the Bx, By, and Bz components along the track with
noise added and as predicted from the L2 model. Darker to lighter colors show tracks from −y to y. (f)–(h) Magnetization models of corresponding L2 inversions
where the color bar represents the total magnetization amplitude, M = + +
M M M
x y z
2 2 2
. The outline of the crater is marked (dashed black).
9
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10. depth extent. The sparse solution enforces a compact feature
and is therefore able to pinpoint the location of the dike very
well, but as expected, it does not extend the feature at depth
(Figures 7(a)–(c)). In places where a dike is visible via imagery
and the goal is to probe whether it is (de)magnetized compared
with the surrounding material, this might be sufficient. In the
one-layer model, we decide to ignore depth resolution and just
focus on locating the dike, which can be achieved exceptionally
well (Figures 7(d)–(f)). Note that the detection of the intrusion
is only possible because the data points are collected in direct
proximity to the feature. For the landed case, we increased the
data point density around the dike as we would in regions
where such a feature is identified, e.g., in imagery. Further-
more, while we model a purely vertical and horizontally
symmetric feature, we would expect some lateral extent due to
smaller intrusions and heating in the surrounding crust that
would increase the magnetization area and thus the area in
which the feature can be detected.
4.3. Scenario 3: Layering
In the last scenario, we investigate the effect of layers that
are much wider than the helicopter altitude (Figure 8(b)).
Generally, a magnetic survey detects lateral gradients
(Equation (1)) in magnetization. Thus, a uniformly magnetized
layer of infinite extent or a uniformly magnetized shell does not
lead to a magnetic field signature (Affleck 1958; Parker 1977).
As a result, the traversing helicopter measures a (close to) zero
magnetic field in the center of the individual layers
(Figure 8(a)). Inversions without a priori information will
therefore map layer edges rather than the layers themselves.
This effect is clearly visible in the data (Figures 8(a)–(d)), and
due to the large direction and amplitude changes across the
layer boundaries, the amplitude of the magnetic field signal is
larger than for previous examples, despite a similar maximum
amplitude of magnetization. Note that the noise floor of 0.1 nT
is low compared to the signal associated with magnetization in
this example (Figures 8(b)–(d)). The edge effect is also clearly
visible in the L2 inversion (Figures 8(f)–(h)), and the model
predictions fit the data very well (again, as result of a
comparably low noise floor). Between approximately 50 and
200 m depth, the direction of the layers can be recovered, while
the inversion does not recover near surface magnetizations, as
observed previously. The sparse inversion generally localizes
what we see in the L2 inversion. Again, transitions can be
mapped, and the magnetization direction is approximated
reasonably well. Lastly, the domain mapping methodology can
obtain a solution that matches the data very well (Figures 9(d)–
(f)) even if only a few data are collected, as long as all units are
covered. Even if no information on the direction or amplitude is
provided a priori, only the layer outlines, the magnetization can
Figure 5. Scenario 1–Crater sparse and parametric inversion. Recovered models of total magnetization M for the (a)–(c) sparse and (d)–(f) parametric inversion for the
different sampling geometries (a) and (d) regular grid, (b) and (e) three flight tracks, and (c) and (f) a few individual data points collected on the ground (orange). The
outline of the crater is marked (dashed black). Note the change in color bar limits.
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11. be recovered well for all survey scenarios. This method also
performs very well for high background noise (not shown) but
requires good understanding of the geometry of the layers.
5. Discussion: Magnetometer Mission Considerations
5.1. Dealing with Noise
We now consider varying levels of noise. Previous figures
assume a noise level of 0.1 nT, and we now investigate the
effect of 0, 0.5, and 1 nT (Figure 10) for the initial L2 inversion
for the crater scenario. While 0.1 nT is approximately 10% of
the measured peak magnetic field, the increased noise level is
substantial with respect to the crater signal. However, we can
recover a coherently magnetized structure such as that shown in
this example, although the magnetic field amplitude and
random noise are of similar order. This is particularly
encouraging, as we expect signatures associated with the
surface magnetic field to mostly be stronger than what is
modeled here.
Generally, noise sources are an important consideration for
any magnetics mission. Above, we have described noise due to
external magnetic fields; those fields will be local time–
dependent and often vary on different timescales. If the
duration of a helicopter traverse is much longer than the
fluctuations due to the external magnetic field, we would expect
the full traverse data to be affected, including crustal field
anomalies. While this might lead to an under- or overestimation
of the anomaly amplitude, the detection of the anomaly itself
would not be impacted, except for weak magnetization sources.
Periodic fluctuations on the order of minutes (i.e., comparable
to a flight traverse) or seconds could affect the measurements.
At InSight, these have been observed and were on the order of
up to a few nanoteslas, but they only occur irregularly and
usually at dusk/dawn and at night. Ionospheric fluctuations are
expected, and they are strongest during the day. Hence, to
mitigate external magnetic field effects, we recommend
sampling at magnetically quiet times of the day or, if possible,
at night. Any ROI should be covered by multiple tracks and, if
possible, at similar local times. External field characterization
while on the ground can be used to (i) identify the most
opportune times for measurements and (ii) estimate the
uncertainties associated with longer-timescale signals.
Figure 6. Scenario 2 –Dike intrusion L2 inversion. (a) Different components and magnetic field amplitudes of synthetic magnetic field data in the x–y plane from (b) a
magnetization model of a crater with a total magnetization amplitude of 10 A m−1
. (b)–(d) Different survey scenarios, (b) mesh, (c) in-flight, and (d) landed, for the
Bx, By, and Bz components along a track with noise added and as predicted from the L2 model as labeled. Darker to lighter colors show tracks from −y to y. (f)–(h)
show the magnetization models of corresponding L2 inversions. The outline of the dike intrusion is marked (dashed black).
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12. 5.2. Cleanliness Considerations
Artificial sources can be substantial, and thorough cleanli-
ness programs are essential to characterize or account for them
as best as possible. Here we do not provide recommendations
on cleanliness procedures but acknowledge that artificial
sources might be substantial, especially for taking measure-
ments along the flight traverse, and briefly discuss some
important considerations. While low-altitude platform surveys
are routinely used on Earth, we would like to note that
commercial terrestrial drones are generally not designed with
magnetic cleanliness in mind. Extensive characterizations of
thermal effects and electric and magnetic interference are
common for spacecraft missions carrying magnetometers,
while terrestrial instrumentation is rarely characterized to the
same degree. Spacecraft carrying science-grade magnetometers
undergo magnetic cleanliness programs in order to make sure
that the artificial sources are smaller than the required
measurements. Such magnetic cleanliness programs are best
approached from a systems-engineering perspective, working
with the spacecraft, magnetometer instrument, and science
teams to select best approaches (Acuña 2004).
The requirements for a mission very much depend on
mission goals and landing location. Crustal magnetic fields are
spatially inhomogeneous and can be very strong locally. If
landing were to occur in such a location, these fields would be a
dominant contribution compared with time-varying external
fields and precharacterized artificial fields created by the
lander/helicopter. While the latter can be large, any mission
measuring ambient magnetic fields undergoes thorough
investigation of artificial contributions. The requirement for
accuracy of such a characterization depends on science
questions. For example, accuracy to within several nanoteslas
would likely be sufficient if only changes in the crustal field are
of interest for a survey site in a moderately magnetized region.
The noise discussion in the above subsection is relevant here.
Finally, deployable, nonmagnetic booms should be consid-
ered to move the magnetometer as far as possible from other
instruments and helicopter current sources. The boom length
and design will again depend on the exact measurement
requirements and the nature of the artificial signals on the
platform. For example, tethers have also been suggested, which
would allow the magnetometer to dangle from the helicopter
while traversing. In this case and ideally, inertial measurement
Figure 7. Scenario 2–Dike intrusion sparse and single-layer inversion. Recovered magnetization models for the (a)–(c) sparse and (d)–(f) single-layer inversion for the
different sampling geometries (a) and (d) regular grid, (b) and (e) three flight tracks, and (c) and (f) a few individual data points collected on the ground (orange).
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13. units could determine the instrument’s position in space and
allow for three component measurements; when landed, the
position of the instrument could be established once and allow
for reduced data collection (i.e., no constant positioning is
required). The amplitude of the field would always be available
and not rely on positioning. Additional lightweight magnetic
sensors with varying distances to the electronics could provide
further information on the fields generated by the helicopter
and thus help characterize and subtract those fields (Ness et al.
1971); this, of course, would add payload mass, and this trade-
off would have to be carefully considered. In all cases, the
detailed design would be a collaboration between science,
instrument, and spacecraft teams.
5.3. Including Other Instruments
Magnetic field data in the context of other measurements will
offer the most comprehensive picture of the survey site (see
also Table 1). While we do not attempt to list all possible
additional instruments, we suggest a selection of data sets that
could aid interpretations of magnetic field measurements.
The combination of existing orbital high-resolution imagery
with an added camera on the helicopter is key for interpretation
of geological surface features and their associated magnetiza-
tion (e.g., Langlais & Purucker 2007; Lillis et al. 2013;
Mittelholz et al. 2020a). We have shown that the inclusion of
prior knowledge from imagery can greatly benefit our modeling
efforts. As a further example, if we can identify a magnetic
field signal associated with a pebble, rock, or block, one could
use imagery to estimate its volume and thus magnetization.
This would require one to move/fly around the rock at
increments on the order of the size of the pebble. A similar
experiment was suggested but not attempted with the robotic
arm on the InSight lander (Golombek et al. 2023). Here the
measurements at different distances from the pebble were
planned by moving the pebble with the robotic arm. The
magnetization amplitude depends on the volume extent of the
magnetized structure, which can easily be misrepresented, often
leading to underestimations of magnetization (see results of L2
inversions). The pebble would provide an alternative and
simple way of getting at magnetization from which material
properties and possibly the magnetizing field can be inferred.
Other instrumentation that would provide increased science
return includes spectrometers that directly identify the
elemental and/or mineralogical characteristics of surface
material. This additional information can help address the
carrier of magnetization and possibly magnetization acquisition
mechanisms (Table 1). Landing sites with differing ROIs, e.g.,
highly altered versus volcanic material, would offer ideal
survey sites. However, we note that spectrometers inform on
surface composition, and combining these observations with
the results of magnetic field inversions would require the
surface layer to be magnetized. Global models for magnetiza-
tion source depth mostly predict magnetization kilometers
below the surface, especially in the southern hemisphere, with
some regions of more surficial magnetization mostly in the
Figure 8. Scenario 3–Layers L2 inversion. (a) Different components and magnetic field amplitude of synthetic magnetic field data in the x–y plane from (b) a
magnetization model of a crater with a total magnetization amplitude of 10 A m−1
. (b)–(d) Different sampling scenarios, (b) regular grid, (c) in-flight, and (d) landed,
for the Bx, By, and Bz components along a track with noise added and as predicted from the L2 model as labeled. Darker to lighter colors show tracks from −y to y.
(f)–(h) show the magnetization models of corresponding L2 inversions. Layer transitions are marked (red dashed).
13
The Planetary Science Journal, 4:155 (16pp), 2023 August Mittelholz et al.
14. Figure 9. Scenario 3–Layers sparse and domain inversion. Recovered magnetization models for the (a)–(c) sparse and (d)–(f) domain mapping inversion for the
different sampling geometries (a) and (d) regular grid, (b) and (e) three flight tracks, and (c) and (f) a few individual data points collected on the ground (orange).
Figure 10. Scenario 1–Crater with increasing noise floor. (a)–(c) show the magnetic field signal for all three tracks due to the crater (solid line), simulated
measurements including noise (dots), and the magnetic field from the recovered L2 model (dashed) at 1 m above the surface for all components. Darker to lighter
colors show tracks from −y to y. (d)–(f) Recovered magnetization models for the L2 inversion equivalent to Figure 4.
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The Planetary Science Journal, 4:155 (16pp), 2023 August Mittelholz et al.
15. north (Gong & Wieczorek 2021). However, the source depth
uncertainties in such models are large (Gong &
Wieczorek 2021). Locally, magnetization has been shown to
be at least partially surficial in the Medusa Fossae formation,
particularly Lucus Planum (Mittelholz et al. 2020a; Ojha &
Mittelholz 2023), and in comparison with orbital spectrometer
data, composition has been shown to correlate with higher
magnetic fields (AlHantoobi et al. 2021).
Lastly, information on physical properties at depth could be
obtained with a gravimeter. Because gravity informs on density
and thus the compositional constraints of rock, combined
magnetic–gravity surveys are particularly informative in
addressing the origin of magnetization. Also, because both
fields fall off differently with distance to the source, they have
different depth sensitivities. Joint modeling techniques for the
combination of petrophysical/geological and geophysical data
have been shown to more accurately represent physical
properties and could provide further modeling strategies that
can make use of combined data sets (e.g., Lelièvre &
Farquharson 2016; Astic & Oldenburg 2019; Astic et al.
2020; Lösing et al. 2022; Moorkamp 2022).
6. Conclusion and Recommendations
We have shown that a range of methodologies will be useful
to interpret magnetic field data collected by a helicopter. To
summarize the lessons learned from our modeling and previous
magnetic field data from Mars, we list recommendations for
future helicopter surveys.
1. Landed measurements can resolve structures well,
provided the measurements are made at multiple loca-
tions in proximity to the feature. However, data collected
in flight will substantially increase the scientific value of
the data set. Prior investigations of individual ROIs can
be connected with reconnaissance flights that might
uncover unexpected signals that can be used to adapt
future ROIs and flight path planning.
2. Regular characterization of noise on the surface will
greatly aid in separating crustal and external magnetic
field signals. This could be achieved while the helicopter
is charging and should cover times at which sampling is
usually done.
3. Under the assumption that data can be collected in flight,
flight traverses should occur at magnetically quiet times
of the day or, preferably, at night, if possible. To start
with, InSight observations can provide a guide to the
diurnal pattern of external field fluctuations. Regular
external field observations might help refine the timing
for different locations.
4. Repeat measurements along horizontal traverses and
vertical profiles above ROIs would enable robust
identification of crustal magnetization.
5. Magnetic field observations paired with information on
geology, gravity, and/or geochemistry can greatly
enhance the expected science return.
6. Because magnetic fields fall off with distance from their
source, robust modeling greatly benefits from several
flight paths that are slightly offset and/or cover multiple
altitudes.
In summary, helicopter magnetic field surveys represent a
major leap forward in our understanding of the origins of Mars’
crustal magnetic field and thus the evolution of terrestrial
planets.
Acknowledgments
We acknowledge support from Harvard’s Daly Postdoctoral
Fellowship (A.M.), the Natural Sciences and Engineering
Research Council of Canada (C.L.J.), and CNES in the frame
of the InSight mission (B.L.). A portion of this research was
carried out at the Jet Propulsion Laboratory, California Institute
of Technology, under a contract with the National Aeronautics
and Space Administration (80NM0018D0004). We also thank
the open-source community for their ongoing contributions to
SimPEG. The software is available on GitHub: https://github.
com/AnnaMittelholz/Helicopter.
ORCID iDs
Anna Mittelholz https:/
/orcid.org/0000-0002-5603-7334
Lindsey Heagy https:/
/orcid.org/0000-0002-1551-5926
Catherine L. Johnson https:/
/orcid.org/0000-0001-
6084-0149
Jonathan Bapst https:/
/orcid.org/0000-0003-1176-7613
Benoit Langlais https:/
/orcid.org/0000-0001-5207-304X
Robert Lillis https:/
/orcid.org/0000-0003-0578-517X
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