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Depleted shergottites record unique information about the primary composition and differentiation of the mantle of Mars. Their petrology, geochemistry, and cosmic ray exposure and crystallization ages suggest that most of them were excavated by a single young impact in the Amazonian‐aged lava flows of the Tharsis and Elysium volcanic provinces. However, the difficulties of deriving consistent model ages for individual craters and inadequate evaluation of 3‐7 km craters capable of ejecting martian meteorites have not been settled. Here we perform detailed geological investigations and crater statistics in patches of impact melt deposits for potential source craters of depleted shergottites with D > 3 km, especially those in the Tharsis and Elysium volcanic provinces. By excluding the effect of heterogeneous textures across ejecta deposits, which hinder straightforward extraction of superposed production populations, our systematically updated model ages reveal that Chakpar crater at the northern flank of Ascraeus Mons is the best‐fit candidate. The local context of this crater permits establishing a link between the meteorites and specific lava flows. The long‐lived volcanic center here may experience an eruption and/or local deposition hiatus for about 1.8 billion years, and abundant subsurface water existed when the impact occurred at about 1.1 million years. [ABSTRACT FROM AUTHOR]

Gypsum is a common mineral at Gale crater on Mars, currently being explored by the Mars Science Laboratory (MSL) rover, Curiosity. In this paper, we summarize the associations of gypsum with other sulfate minerals (bassanite, anhydrite, jarosite, starkeyite, and kieserite) from the lowest levels of the crater's northern moat zone (Aeolis Palus) up through ~0.8 km of the stratigraphic section in the lower slopes of the sedimentary mound developed around the central peak, Aeolis Mons (informally, Mount Sharp). The analysis is based on results from the CheMin X-ray diffraction instrument on Curiosity, supplemented with information from the rover's versatile instrument suite. Gypsum does not occur with the same frequency as less hydrous Ca-sulfates, likely, in most cases, because of its dehydration to bassanite and possibly to anhydrite. All three of these Ca-sulfate phases often occur together and, along with other sulfates, in mixed assemblages that are evidence of limited equilibration on a cold, dry planet. In almost all samples, at least one of the Ca-sulfate minerals is present, except for a very limited interval where jarosite is the major sulfate mineral, with the implication of more acidic groundwater at a much later time in Gale crater's history. Although observations from orbit reveal a sulfate-rich surface, currently active dark basaltic dunes at Gale crater have only small amounts of a single sulfate mineral, anhydrite. Gale crater has provided the most complete mineralogical analysis of a site on Mars so far, but the data in hand show that Gale crater mineralogy is not a blueprint with planet-wide application. The concurrent study of Jezero crater by the Mars 2020 mission and comparisons to what is believed to be the most extensive deposit of gypsum on Mars, in the dune fields at the north polar ice cap, show significant diversity. Unraveling the stories of gypsum and other sulfates on Mars is just beginning. [ABSTRACT FROM AUTHOR]

The Mars 2020 Perseverance Rover imaged diagenetic textural features in four separate sedimentary units in its exploration of the 25‐m‐thick Shenandoah formation at Jezero Crater, Mars, that we interpreted as probable concretions. These concretions were most abundant in the Hogwallow Flats member of the Shenandoah formation and were restricted to the light‐toned, platy, sulfur‐cemented bedrock at outcrop surfaces, whereas the finely laminated, darker toned, mottled and deformed strata lack concretions. The concretions also had a wide range of morphologies including concentric, oblate, urn, and spheroidal shaped forms that were not clustered, and ranged in size from ∼1 to 16 mm with a median of 2.65 mm. The elemental composition of the concretions compared to the bedrock had greater abundance of magnesium and calcium salts, silicates, and possibly hematite. We compared these Jezero Crater concretions to the geochemistry of concretions from previously published studies and from two new terrestrial analog sites (Gallup Formation, New Mexico and Torrey Pines, California). In addition, we measured organic carbon content of three terrestrial sedimentary analogs of increasing age that contain concretions (Torrey Pines (Pleistocene), Gallup Formation (∼89 Ma), and Moodies Group (∼3.2 Ga)). All measured concretions contained significant concentrations of organic carbon with the maximum organic carbon content (∼2 wt. % Total organic carbon) found in the Moodies Group concretions. Organic carbon abundances in terrestrial concretions was controlled more by the formation mechanism and relative timing of concretion development rather than deposit age. These findings suggested that concretions at Jezero Crater reflect local sites of enhanced biosignature preservation potential. Plain Language Summary: The Perseverance Rover discovered concretions in its exploration of the rock packages at Jezero Crater, Mars and one of the sample return cores was collected from concretion‐rich bedrock. Concretions are resistant cement in the rock that are found in many shapes (usually spherical or oblate) and range from millimeter to meter size scales on Earth; they can be formed through inorganic water‐rock reactions or facilitated by microbial metabolisms. We documented the abundance, size, composition, and shape of the concretions to understand how these features were formed. We found that the concretions are mixtures of salts, clay minerals, and iron oxides. We compared these results to terrestrial concretions with similar mineral compositions and measured the organic carbon in four terrestrial analogs. Comparisons with terrestrial concretions in this study and the literature suggested that the concretion composition in Jezero Crater could have high organic preservation potential. Thus, the concretions in Jezero Crater may retain organic carbon and other biosignatures and might therefore be considered as high priority samples of astrobiological interest out of the current sample suite for return to Earth. Key Points: Jezero Crater concretions are variably enriched in Si, Ca, and Mg salts, and Fe oxidesTerrestrial concretions of similar mineralogy analyzed in this study contain significant organic carbon phasesBased on terrestrial analogs, Jezero Crater concretions may represent sites of enhanced biosignature preservation potential [ABSTRACT FROM AUTHOR]

Meteoroid impacts produce different types of fractures and damage zones beneath impact craters. The 3D geometry of these features reflects the trajectory and energetics of an impact event. In this study, we mapped the impact damage zone beneath the 1.88‐km‐diameter Lonar crater, emplaced in Deccan basalts, using Ambient Noise Tomography (ANT). A network of 23 broadband seismic stations in and around the crater yielded a 1.2 km deep 3D shear wave velocity (VS) image covering ∼7 km by ∼5 km area. It revealed ∼500–900‐m‐thick heterogeneous target basalt flows, underlain by an undulating Archean granite‐gneiss basement. A substantial reduction in VS is observed beneath the crater. The original crater floor was found at a depth of 400 m below the crater rim, which is filled by impact breccia and lake sediments. Beneath the original floor, we found an oval‐shaped, asymmetric 200‐m‐thick lensoidal low‐velocity layer with a tongue‐like feature beneath the southwestern ejecta blanket. The damage zone is inferred to have formed as a result of oblique impact, in which the projectile arrived from northeast to southwest direction. The VS reduction in the low‐velocity layer was used to calculate the amount of impact damage in it. The oblique impact produced a more elevated southwestern crater rim. Impact‐related near‐surface fracture zones up to a radial distance of >1 km beneath the ejecta blanket were also found. We suggest that impact damage beneath impact craters on Earth and other planetary bodies may be imaged using ANT. Plain Language Summary: Impact craters are ubiquitous on planetary surfaces. The impact produces both surface and sub‐surface changes, including fracturing and damage beneath the crater floor. The 3D geometry of the damage zone depends on the impact angle and velocity. While vertical impacts generate symmetric damage zones beneath the craters, oblique impacts produce asymmetrical damage zones with greater damage in the downrange direction. Field geological mapping provides limited information about these features, while the Ambient Noise Tomography (ANT) brings out a complete shape and size of the damage zone in the sub‐surface. The shear wave velocity image also provides the characteristics of target rocks within and outside the impact crater. In this work, we carried out the ANT study of Lonar crater, emplaced in Deccan basalts in India, using a network of 23 broadband seismometers. This study revealed a ∼500–900‐m‐thick heterogeneous basaltic target underlain by an Archean granite‐gneiss basement, and an asymmetric damage zone beneath ∼400‐m‐deep original crater floor because of southwest directed oblique impact. We quantified the amount of impact damage beneath the original crater floor. The ANT can be used for imaging damage zones beneath impact craters on Earth and other solid planetary bodies, thus providing more insight into impactor trajectories. Key Points: Ambient noise tomography reveals a 500–900 m thick heterogeneous basaltic target underlain by Archean granite basement beneath Lonar craterAn asymmetric damage zone is found beneath the 400 m deep original crater floor filled by impact breccia and lake sedimentsAsymmetric topography and impact damage zone geometry are consistent with a southwest‐ward oblique impact trajectory [ABSTRACT FROM AUTHOR]

The Mars 2020 Perseverance rover has explored fluvio‐lacustrine sedimentary rocks within Jezero crater. Prior work showed that igneous crater floor Séítah and Máaz formations have mafic mineralogy with alteration phases that indicate multiple episodes of aqueous alteration. In this work, we extend the analyses of hydration to targets in the Jezero western fan delta, using data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectrometer. Spectral features, for example, sulfate and hydration peak positions and shapes, vary within, and across the crater floor and western fan. The proportion of targets with hydration associated with sulfates was approximately equal in the crater floor and the western fan. All hydrated targets in the crater floor and upper fan showed bimodal hydration peaks at ∼3,200 and ∼3,400 cm−1. The sulfate symmetric stretch at ∼1,000 cm−1 coupled with a hydration peak at ∼3,400 cm−1 indicate that MgSO4·nH2O (2 < n ≤ 5) is a likely hydration carrier phase in all units, perhaps paired with low‐hydration (n ≤ 1) amorphous Mg‐sulfates, indicated by the ∼3,200 cm−1 peak. Low‐hydration MgSO4·nH2O (n = 1–2) are more prevalent in the fan, and hydrated targets in the fan front only had one peak at ∼3,400 cm−1. While anhydrite co‐occurs with hydrated Mg‐sulfates in the crater floor and fan front, hydrated Ca‐sulfates are observed instead at the top of the upper fan. Collectively, the data imply aqueous deposition of sediments with formation of salts from high ionic strength fluids and subsequent aridity to preserve the observed hydration states. Plain Language Summary: The Mars 2020 Perseverance rover has explored a fan delta deposit in the Jezero crater where a lake was present in the past. In this work, we use the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectroscopy instrument on the rover to determine the minerals that contain water in the form of H2O and/or OH. These hydrated minerals are indicators of interactions of rock with water and inform us how the environmental conditions and the habitability of Jezero crater evolved over time. Hydrated Mg‐sulfates MgSO4·nH2O (2 < n ≤ 5) are observed in both the crater floor and the western fan. Mg‐sulfates of lower hydration degree (n = 1–2) are more commonly found in the western fan, particularly the fan front. Hydrated Ca‐sulfate is found only close to the top of the fan. These changes in sulfate degree of hydration and/or cations from the floor to the fan are evidence of multiple past fluid events and chemistries at Jezero crater. Key Points: MgSO4·nH2O (2 < n ≤ 5) are found in the Jezero fan and floor while low‐hydration MgSO4·nH2O (n = 1–2) are more commonly found in the fanHydrated Ca‐sulfates are found only in the upper fanThe diverse phases imply salt formation from high ionic strength fluids and subsequent aridity to preserve the observed hydration states [ABSTRACT FROM AUTHOR]

Seismic observations of impacts on Mars indicate a higher impact flux than previously measured. Using six confirmed seismic impact detections near the NASA InSight lander and two distant large impacts, we calculate appropriate scalings to compare these rates with lunar-based chronology models. We also update the impact rate from orbital observations using the most recent catalog of new craters on Mars. The snapshot of the current impact rate at Mars recorded seismically is higher than that found using orbital detections alone. The measured rates differ between a factor of 2 and 10, depending on the diameter, although the sample size of seismically detected impacts is small. The close timing of the two largest new impacts found on Mars in the past few decades indicates either a heightened impact rate or a low-probability temporal coincidence, perhaps representing recent fragmentation of a parent body. We conclude that seismic methods of detecting current impacts offer a more complete dataset than orbital imaging. [ABSTRACT FROM AUTHOR]

Crater detection is useful for research into dating a planetary surface's age and geological mapping. The high-resolution imaging camera (HiRIC) carried by the Tianwen-1 rover provides digital image model (DIM) datasets with a resolution of 0.7 m/pixel, which are suitable for detecting meter-scale craters. The existing deep-learning-based automatic crater detection algorithms require a large number of crater annotation datasets for training. However, there is currently a lack of datasets of optical images of small-sized craters. In this study, we propose a model based on the Segment Anything Model (SAM) to detect craters in Tianwen-1's landing area and perform statistical analysis. The SAM network was used to obtain a segmentation mask of the craters from the DIM images. Then non-circular filtering was used to filter out irregular craters. Finally, deduplication and removal of false positives were performed to obtain accurate circular craters, and their center's position and diameter were obtained through circular fitting analysis. We extracted 841,727 craters in total, with diameters ranging from 1.57 m to 7910.47 m. These data are useful for further Martian crater catalogs and crater datasets. Additionally, the crater size–frequency distribution (CSFD) was also analyzed, indicating that the surface ages of the Tianwen-1 landing area are ~3.25 billion years, with subsequent surface resurfacing events occurring ~1.67 billion years ago. [ABSTRACT FROM AUTHOR]

Impacts into layered targets may generate "concentric craters" where a wider outer crater in the top layer surrounds a smaller, nested crater in the basement, which itself may be complex or simple. The influence of target on cratering depends on the ratio of target strength to lithostatic stress, which, in turn, is affected by gravity, target density, and crater diameter. When this ratio is large, the crater size is primarily determined by target strength, whereas gravitational forces dominate when the ratio is small. In two‐layer targets, strength may dominate in one or both layers, whereby the outer crater develops in the weaker top layer and the nested crater in the stronger substrate. However, large natural craters that should be gravity‐dominated in both cover strata and substrate may be concentric, the reasons for which are not yet fully understood. We performed qualitative impact experiments at 10–502 G and 1.8 km/s with the Boeing Corp. Hypervelocity centrifuge gun, and at 1 G and 0.4 km/s with the CAB CSIC‐INTA gas gun into layered sand targets of different compositions and grain densities but similar granulometry to analyze gravity‐dominated cratering. The results are compared with iSALE‐2D numerical simulations and natural craters on Earth and Mars. We show that target layering also affects the excavation process and concentric crater formation in gravity‐dominated impacts. The most important factors are the density and internal friction of each target layer, respectively. We propose that this is also valid for natural craters of sizes that should make their formation gravity‐dominated. Plain Language Summary: Concentric impact craters show a "soup‐plate" or "inverted sombrero" shape that forms on planetary surfaces with distinct subsurface layers. Generally, a deep inner crater forms in the substrate and a shallower, broader outer crater forms in the upper layer. The shape is obtained either from extensive post‐impact collapse of the upper, often weaker layer, or already during crater excavation, which is the focus of this study. The ratio of outer to inner diameter in the latter craters can be used to probe the depth of the upper layer and the contrast in material properties to the substrate. However, the controls on the relative size of the inner and outer craters are not well understood. While the formation of natural concentric craters is often attributed to a change in cohesive strength between the upper and lower layers, we show through impact experiments and numerical simulations that concentric craters can also form in cohesionless targets with a contrast in both density and friction coefficient between the layers. This provides an additional mechanism for concentric crater formation that may explain the development of some large, gravity‐dominated, naturally occurring concentric craters on Earth, Mars and elsewhere. Key Points: Concentric craters are not only due to strength differences between layers but also observed in cohesionless, gravity‐dominated targetsThis may explain the occurrence of large gravity‐dominated concentric craters on Earth, Mars and elsewhereKey factors affecting the concentric growth in these cases are the density and internal friction of each target layer, respectively [ABSTRACT FROM AUTHOR]

Siliceous hot spring deposits, or sinters, deposit from hot spring discharge at Earth's surface and are sites of exceptional preservation of biosignatures. Their macro‐ and micro‐textures are regarded as important evidence of past microbial activities in hydrothermal environments. However, biology mimics do occur, and bona fide microbial textures could be destroyed by subsequent diagenesis or other post‐depositional processes. Thus, it is paramount to narrow the search for prospective Martian silica‐rich deposits that may contain biosignatures from both orbital and rover‐based perspectives. This study investigates hydrothermal deposits in Chile, which are analogs of high‐silica deposits discovered in the Gusev crater on Mars, through remote sensing and laboratory analysis. Results indicate that compositional remote sensing based on multispectral data with a high spatial resolution of <4 m/pixel reflects various concentrations of silica, which assisted in identifying the direction of discharged hydrothermal flows from the vent to the apron. Micro‐infrared mapping of sinters from similar hydrothermal fields linked spectral features to specific textures revealed by scanning electron microscope and chemical compositions confirmed by electron microprobe analysis, indicating that sinters with no shift in their emissivity minimum in the thermal infrared range were more likely to preserve cellular structures. An instrument for collecting multispectral data with higher spatial resolution could aid in characterizing the geologic settings of potential hot springs on Mars. Locating emissivity minima in the infrared regions of silica that do not shift to a lower position would suggest the potential for well‐preserved microbial structures in Martian sinters, if life ever did exist there. Plain Language Summary: Macro‐ and micro‐textures of silica sinters formed in hot springs on Earth are valuable records of microbial activities. Nevertheless, alteration by subsequent processes, some non‐biological, may produce biological mimics. Therefore, identifying sinters with potential biogenic textures is crucial in selecting silica‐rich astrobiological targets. Here, we report orbital‐scale surveying and micro‐scale surveys of silica deposits in Chile, which are comparable to an inferred hydrothermal environment in Gusev Crater on Mars, where the Spirit rover found high‐silica deposits with similar textures. Remote sensing analyses of the El Tatio region provided contextual information regarding silica distribution and its relationship to land surface temperatures and biogenic pigments in the active geothermal area. High‐resolution multispectral data were particularly useful in identifying the flow direction of discharging thermal waters. Detailed spectral and chemical analyses of Chilean sinters suggest that no shift in the position of the minimum feature in the mid‐infrared spectra relates to sinters containing well‐preserved biological textures. This spectral characteristic indicates no substitution of Al for Si, which in turn suggests less likelihood of subsequent processes causing damage to the sinter textures. This study holds promise for identifying future astrobiological targets on Mars from orbital data and onsite spectroscopy. Key Points: High‐resolution multispectral data are helpful in determining the vent‐to‐distal apron geological setting of a hydrothermal siteThe shift of emissivity minima to a lower position in the thermal infrared range may suggest the substitution of Al for Si in silicaHigh‐resolution orbital data and hyperspectral rover‐scale infrared data can aid the search for biosignatures in hydrothermal areas on Mars [ABSTRACT FROM AUTHOR]

We reassessed several orbital topographic data sets for the Perseverance rover landing site at Jezero Crater, Mars to better understand its floor units. Tens‐of‐meters deep topographic anomalies occur in the volcanic floor of Jezero crater and are not a result of impact cratering. Eight km‐scale steep escarpment‐bounded depressions may be locations of paleotopographic highs that were embayed by the volcanic floor lava flows, forming inverted topography from either contemporaneous upward inflation of embaying lavas or later deep scour due to differential erosion over 107−9 years. Five multi km‐scale shallow‐sloped depressions linked by channel‐like forms may record locations of buried paleolakes and channels that predate the volcanic floor units or a drained magma system. These results indicate Jezero experienced multiple closed‐basin or dry phases, allowing erosion of the crater floor and creation of topography, which provides new geologic context for the samples gathered by Perseverance. Plain Language Summary: The Perseverance rover has been on Mars in Jezero Crater for over 2 years collecting rock samples. We reexamined elevation data to better understand the volcanic lava unit on the floor of the crater. We found that the floor is slightly tilted south‐southeast, possibly due to sediment, sourced from the north, beneath the volcanic floor. In the floor we found eight depressions bounded by cliffs, possibly formed by past lava flows around hills of weaker rocks that are now eroded away or by the lavas rising upward around the hills of rock. We also found five large, shallow depressions connected by channels. These might indicate old locations of lakes and rivers before the more recent volcanic activity or a drained magma system. This suggests Jezero Crater experienced alternating phases of being dry and being filled with water, providing key information to help interpret the collected samples. Key Points: Tens‐of‐meters deep topographic anomalies occur in the volcanic floor of Jezero CraterSeveral multi‐km2 scale shallow‐sloped depressions and channels may record lower lake levels or a drained magma systemEight escarpment‐bounded depressions formed by lava embayment of preexisting topography followed by lava inflation or differential erosion [ABSTRACT FROM AUTHOR]

Craters on Mars are a window into Mars' past and the time they were emplaced. Because the crust is heated and shocked during impact, craters can demagnetize or magnetize the crust depending on the presence or absence of a dynamo field at the time of impact. This concept has been used to constrain dynamo timing. Here, we investigate magnetic anomalies associated with craters larger than 150 km. We find that most of those craters, independent of age, exhibit demagnetization signatures in the form of a central magnetic low. We demonstrate a statistically significant association between such signatures and craters, and hypothesize that the excavation of strongly magnetic crustal material may be an important contribution to the dominance of demagnetized craters. This finding implies that the simple presence or absence of crater demagnetization signatures is not a reliable indicator for the activity of the Martian dynamo during or after crater formation. Plain Language Summary: Craters on Mars allow studying the time at which they were emplaced and as such they are a window into Mars' past. Because the crust is heated and shocked during impact and thus recrystallization occurs, craters can demagnetize or magnetize the crust depending on the presence or absence of a dynamo field at the time of impact. A classic magnetization signature is expressed by a magnetic high in the crater interior and the youngest of those craters have been used to constrain dynamo timing. Here, we investigate magnetic anomalies associated with all craters larger than 150 km. We find that most of those craters and independent of age exhibit a demagnetization signature, and fewer a magnetization signature. In general, the largest craters show a demagnetization signature. To explain the dominance of demagnetization signatures we hypothesize that the excavation of strongly magnetic crustal material may be an important process. This finding implies that the simple presence or absence of crater magnetization signatures is not a reliable indicator for dynamo activity and magnetic signatures of craters are dependent on multiple parameters such as crustal thickness. Key Points: Craters on Mars dominantly show demagnetization signaturesLarge craters and thin crust promote magnetic lows in the crater interior irrespective of dynamo activityCrustal excavation is likely an important process that promotes demagnetization signatures [ABSTRACT FROM AUTHOR]

The Mars2020 Perseverance Rover landed successfully on the Martian surface on the Jezero Crater floor (18.44°N, 77.45°E) at Martian solar longitude, Ls, ∼5° in February 2021. Since then, it has produced highly valuable environmental measurements with a versatile scientific payload including the MEDA (Mars Environmental Dynamics Analyzer) suite of environmental sensors. One of the MEDA systems is the PS pressure sensor system, which weighs 40 g and has an estimated absolute accuracy of better than 3.5 Pa and a resolution of 0.13 Pa. We present initial results from the first 414 sols of Martian atmospheric surface pressure observations by the PS, whose performance was found to meet its specifications. Observed sol‐averaged atmospheric pressures follow an anticipated pattern of pressure variation in the course of the advancing season and are consistent with data from other landing missions. The observed daily pressure amplitude varies by ∼2%–5 % of the sol‐averaged pressure, with absolute amplitude 10–35 Pa in an approximately direct relationship with airborne dust. During a regional dust storm, which began at Ls ∼ 135°, the daily pressure amplitude roughly doubled. The daily pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular, analysis of the daily pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations with data from other landers reveals the global scale seasonal behavior of Mars' atmosphere. Plain Language Summary: Mars2020 Perseverance Rover successfully arrived on Mars in February 2021. It landed in an early Martian spring afternoon in a crater north of Mars' equator called Jezero crater. The rover is equipped with meteorological instruments that have so far produced extensive and valuable data for understanding the Martian atmosphere. One of the meteorological instruments is an accurate and precise pressure sensor. The pressure sensor has revealed large changes in the pressure over the seasons that are related to large changes in the actual mass of the Martian atmosphere. This is in line with seasonal pressure changes measured during previous Mars missions and can be explained as the condensation of the atmosphere onto the Martian poles and its subsequent sublimation. On a shorter time scale, the pressure sensor revealed complex pressure changes over a Martian day. These variations are thought to be related to atmospheric dust, whose ubiquitous nature is known to have a strong influence on the Martian climate. As the seasons progressed, the daily pressure variations morphed to exhibit different patterns likely related to the large‐scale regional changes in the atmosphere. Comparison of Perseverance pressure observations with other landers revealed the global nature of the atmosphere. Key Points: The atmospheric pressure observations by Perseverance Rover have proved to be of excellent quality fulfilling expectationsJezero crater pressure exhibits significant differences to other Martian areas likely due to varying regional geography and solar forcingOverall, the diurnal and seasonal atmospheric pressure cycles at Jezero Crater follow an anticipated pattern of pressure variation [ABSTRACT FROM AUTHOR]

The Mars Sample Return mission architecture will utilize three spacecraft to collect, cache, recover, launch, and return to Earth a diversity of regolith and rock samples. However, no comprehensive Mars Microbial Survival (MMS) model currently exists. As an initial effort in building an MMS model, we examined the UV reflectance of 15 spacecraft materials and seven Mars analog soils within the context of the Perseverance mission. Data were used to predict the times required to achieve one lethal dose (syn., Sterility Assurance Level [SAL]; def. as a bioburden reduction of −12 logs). Results suggest that a single SAL dosage of UVC was achieved on exposed surfaces on the upper deck of Perseverance within a few hours to a few sols post‐landing at Jezero Crater. The overall average for UVC reflectance from spacecraft materials was approximately 10%. The overall UVC reflectance from Mars analog soils was measured at 1.3%. The Adaptive Caching Assembly (ACA) on Perseverance is located on the forward edge of the underbelly of the spacecraft. Modeling of the accumulated UVC dosage for the ACA yielded a prediction of reaching one SAL for downward facing surfaces at 93 sols that receive "single‐bounce" UVC photons from the local terrain. The SAL increases to 930 sols if an additional "bounce" of the solar UV irradiation is required to reach a partially protected site in the ACA hardware. The current study is the first to report the UVC reflectance from a diversity of spacecraft materials. Plain Language Summary: A combination of three spacecraft will be used to collect, cache, launch, and return to Earth a diversity of rock and soil samples from Jezero Crater on Mars. The Perseverance rover is currently collecting, characterizing, and caching these samples. We sought to characterize the lethality of the ultraviolet (UV) environment at Jezero Crater to predict if the biocidal UVC (190–280 nm) flux on Mars could sterilize the upper and lower surfaces of the rover. The results suggest that the upper deck of the Perseverance rover exposed to direct solar UVC irradiation was sterilized within a few hours to a few sols on the Martian surface. Reflected solar UVC irradiation from spacecraft materials and soils (i.e., average UV reflectance of spacecraft materials and analog Mars soils were measured at 10% and 1.3%, respectively) is likely to kill the microorganisms attached to shielded or shaded surfaces. Shaded surfaces on the upper deck of Perseverance were likely sterilized within 8.3 sols (post‐landing), while the sampling equipment on the underside of Perseverance likely required at least 93 sols to achieve one lethal dose of UVC irradiation. Key Points: Reflected UVC can sterilize the undersides of landed roversSterilization can reach −12 logs within a few tens of sols on upper surfacesSterilization can reach −12 logs for the undersides of spacecraft within a few hundred sols [ABSTRACT FROM AUTHOR]

The Elysium Planitia, located in the transition zone between the northern and southern hemispheres, is one of the key areas for studying the stratigraphic structure and geological history of Mars. Previous studies have shown that this plain has undergone complex surface modification processes including fluvial and volcanic processes, and systematic progress has been made in the study of macro-geological processes. However, there are relatively few studies on the regional structure of the plain, which restricts our understanding of the regional geological processes. A buried impact crater in the central part of the Elysium Planitia could have recorded the surface modification process since the formation of the impact crater; however, it is difficult to distinguish the subsurface stratigraphy due to the weak orbital radar reflection signal. In this study, we denoised Shallow Radar data and obtained a radargram with clear subsurface reflectors. We estimated the permittivity of subsurface materials via a multilayer reflection model. The results show that two subsurface reflectors divide the structure of the buried impact crater into three layers (overlying layer, underlying layer, and bottom layer). The shallow subsurface reflector covers almost the whole impact crater, while the deep subsurface reflector covers only the southwest part of the impact crater. Combining the permittivity inversion results with the geological background of lava activity in the Elysium Planitia area, we argue that the overlying layer may be a mixture of regolith and lava flow with low density, while the underlying layer and bottom layer are dense lava flows. The reflector between the underlying layer and bottom layer is probably a thin deposit derived from weathering between two lava activities, and its possible formation mechanism is as follows: the crater rim and peripheral ejecta has undergone relatively strong wind erosion and the eroded material was transport to the southwestern part of the impact crater, forming continuous thin deposits, between the emplacements of two lava flows. This is consistent with the wind erosion environment prevailing at low latitudes in the Late Amazonian of Mars. This study uses processed orbital radar data, dielectric property inversion, and geological structure interpretation of regional buried impact craters as a local example to demonstrate how radar data can be used to understand regional depositional processes, and it serves as a reference for studying the geological history of similar regional structures on Mars. [ABSTRACT FROM AUTHOR]

During its first year of operation, the Perseverance rover explored the cratered and fractured floor of Jezero crater on Mars. Here, we report the use of the Scanning Habitability Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) imaging system that includes two high‐resolution cameras, the Autofocus and Contextual Imager (ACI) and Wide Angle Topographic Sensor for Operations and eNgineering (WATSON). ACI is a fixed focus gray scale imager with a resolution of 10.1 μm/pixel whereas WATSON is a variable field of view, variable focus imager capable of resolution down to 14 μm/pixel. WATSON is a reflight of the MArs Hand Lens Imager (MAHLI) imager and has similar capabilities. During first‐time activities, WATSON was used to support both science and engineering operations related to sample and abrasion patch assessment and sample collection and caching. WATSON also documented the deployment of the Ingenuity helicopter. The Crater Floor Campaign identified two primary rock units, the Máaz formation and the Séítah formation, which have been interpreted as lava flows and an olivine cumulate, respectively. Interpretation of rock textures with WATSON and ACI images was limited to abraded surfaces because unmodified outcrop surfaces (herein termed "natural surfaces") show high degrees of dust covering, wind abrasion, and coating by secondary mineral products. WATSON and ACI images support the hypothesis that the material of both the Máaz and Séítah formations consists of largely aqueously altered mafic materials with varying igneous origins. Plain Language Summary: The SHERLOC imaging system has been used for a variety of tasks during the first year of operations as part of the Perseverance rover's mission to Jezero Crater. It has been used during scientific observations to understand textures documenting the aqueous alteration history of the crater. It has also been used to support operations by documenting the deployment of the Ingenuity helicopter and the utilization of the sampling and caching hardware. Key Points: High‐resolution imaging is a critical element of rover operationsWATSON imaging has been used for support of both science and engineering operationsImaging provides key context for the understanding of geochemical measurements [ABSTRACT FROM AUTHOR]

Craters are the most prominent geomorphological features on the surface of celestial bodies, which plays a crucial role in studying the formation and evolution of celestial bodies as well as in landing and planning for surface exploration. Currently, the main automatic crater detection models and datasets focus on the detection of large and medium craters. In this paper, we created 23 small lunar crater datasets for model training based on the Chang'E-2 (CE-2) DOM, DEM, Slope, and integrated data with 7 kinds of visualization stretching methods. Then, we proposed the YOLO-Crater model for Lunar and Martian small crater detection by replacing EioU and VariFocal loss to solve the crater sample imbalance problem and introducing a CBAM attention mechanism to mitigate interference from the complex extraterrestrial environment. The results show that the accuracy (P = 87.86%, R = 66.04%, and F 1 = 75.41%) of the Lunar YOLO-Crater model based on the DOM-MMS (Maximum-Minimum Stretching) dataset is the highest and better than that of the YOLOX model. The Martian YOLO-Crater, trained by the Martian dataset from the 2022 GeoAI Martian Challenge, achieves good performance with P = 88.37%, R = 69.25%, and F 1 = 77.65%. It indicates that the YOLO-Crater model has strong transferability and generalization capability, which can be applied to detect small craters on the Moon and other celestial bodies. [ABSTRACT FROM AUTHOR]

We demonstrate the capabilities of a published MADNet monocular height estimation network in producing a refined digital terrain model (DTM) mosaic at 50 cm/pixel resolution for the Mars 2020 Perseverance rover landing site in Jezero crater on Mars. Our approach utilizes the publicly available Mars 2020 Terrain Relative Navigation (TRN) High‐Resolution Imaging Science Experiment (HiRISE) Digital Terrain Model (DTM) mosaic, which was originally created by the United States Geological Survey (USGS) Astrogeology Science Centre. Our resultant HiRISE MADNet DTM mosaic is strictly matched with the original HiRISE TRN DTM and orthoimage mosaics. These mosaics are themselves co‐aligned with the USGS TRN Context Camera (CTX) based DTM and orthoimage mosaics, as well as the ESA/DLR/FUB (European Space Agency/German Aerospace Center/Free University Berlin) High Resolution Stereo Camera (HRSC) level 5 DTM and orthoimage mosaics. In this paper, we provide a brief description of the technical details, and present both visual and quantitative assessments of the refined MADNet HiRISE Jezero DTM mosaic product. This DTM product is now publicly available at http://dx.doi.org/10.17169/refubium-38359. Key Points: We demonstrate the capabilities of a published MADNet monocular height estimation network in producing a refined digital terrain model mosaic at 50 cm/pixel resolution for the Mars 2020 Perseverance rover landing site in Jezero crater on MarsThe resultant 50 cm/pixel digital terrain model mosaic demonstrates significant improvements in effective resolution and artifact elimination compared to the publicly available Mars 2020 Terrain Relative Navigation TRN High‐Resolution Imaging Science Experiment digital terrain modelThe resultant digital terrain model mosaic has been made publicly available at http://dx.doi.org/10.17169/refubium-38359 [ABSTRACT FROM AUTHOR]

In situ geologic context mapping based on rover and helicopter observations provides documentation of a nearly continuous record of geology and exposed surface structure over a 120 m‐wide corridor along the traverse of the Mars 2020/Perseverance rover. The results record the geologic context of Mars 2020 campaign sites and sample sites, including the local extent of bedrock outcrops, stratigraphy, attitude, and structure from imaging and rover‐based remote sensing, and outcrop lithology based on in situ proximity science. Mapping identifies a sequence of igneous lithologies including (a) early mafic, possibly intrusive, rocks; (b) pervasively fractured and deeply altered massive bedrock of undetermined protolith; (c) buried and exhumed lava flows with pahoehoe and aa textures; (d) several varieties of regolith; and (e) small impact craters. Plain Language Summary: Reconnaissance‐type geologic mapping along the traverse of Perseverance on the Jezero Crater floor is adapted from field geologic methods used on Earth and modified to account for the geometry of rover‐based imaging. The final field geologic map records bedrock and surficial geology, contacts, and structures over a 120‐m wide strip along the traverse. Most of the lithologies are igneous, including possible intrusive mafic rocks, deeply weathered massive rocks of unknown original lithology, and lava flows. Stratigraphy determined from mapping together with the observed inclination of layers identifies either uplift or draping of the section centered in the elevated older terrain. The final map information provides ground‐truth geologic context for the first eight samples collected for return to Earth. Key Points: In situ mapping from the rover observations on Mars uses field geologic mapping methodsDocuments the geologic context of samples and the crater floor traverse of PerseveranceDevelops methods applicable to future robotic and human traverses on planetary surfaces [ABSTRACT FROM AUTHOR]

Crater mapping using neural networks and other automated methods has increased recently with automated Crater Detection Algorithms (CDAs) applied to planetary bodies throughout the solar system. A recent publication by Benedix et al. (2020, https://doi.org/10.1029/2019ea001005) showed high performance at small scales compared to similar automated CDAs but with a net positive diameter bias in many crater candidates. I compare the publicly available catalogs from Benedix et al. (2020, https://doi.org/10.1029/2019ea001005) and Lee and Hogan (2021, https://doi.org/10.1016/j.cageo.2020.104645) and show that the reported performance is sensitive to the metrics used to test the catalogs. I show how the more permissive comparison methods indicate a higher CDA performance by allowing worse candidate craters to match ground‐truth craters. I show that the Benedix et al. (2020, https://doi.org/10.1029/2019ea001005) catalog has a substantial performance loss with increasing latitude and identify an image projection issue that might cause this loss. Finally, I suggest future applications of neural networks in generating large scientific datasets be validated using secondary networks with independent data sources or training methods. Plain Language Summary: I have compared two computer programs that use neural networks to identify craters on solar system bodies. The crater catalogs created by these programs have been previously compared against an existing human‐made catalog to measure their performance, but each comparison used a different method making it challenging to understand the difference between the catalogs. In this paper, I use the comparison methods from these two independent papers, discuss where the catalogs agree and disagree, and suggest why they disagree. I emphasize the need for more accurate and consistent methods to validate automatic crater‐mapping programs, especially when it is impractical for humans to check the craters found by automated methods. Key Points: The apparent performance of automatic crater detection algorithms is sensitive to the choice of metric used to gauge the performanceFeature Detection Algorithms trained to find spatial features should be used with appropriately projected images where possibleAs neural networks extend crater detection beyond practical human limits, validating their results with a independent networks is critical [ABSTRACT FROM AUTHOR]

Fluvial channel belts, the deposits accumulated in rivers surrounded by floodplain deposits, are sensitive environmental recorders. Across Mars, wind has exposed ancient channel belts via the preferential erosion of floodplain strata, creating landforms called fluvial ridges. However, river deposits observed by the Mars rover Curiosity are instead exposed along a series of steep slopes and shallow benches, and short, truncated ridges we call noses. Here, we tested the hypothesis that these exposures record channel‐belt exhumation with a preferential direction of scarp retreat (a slope‐aspect control), in contrast with models of fluvial‐ridge formation. Using a landscape evolution model sensitive to lithology and an Earth‐analog 3D‐seismic‐reflectance volume imaging fluvial stratigraphy, we generated synthetic erosional landscapes where channel‐belt exhumation created benches and noses rather than fluvial ridges, depending on the orientation of belts relative to the preferential direction of scarp retreat, which we suggest is set by winds steered along crater topography. Plain Language Summary: Ancient river deposits exist across Mars and can be identified in satellite data by erosional landforms called fluvial ridges. Fluvial ridges take the shape of ancient river deposits, and are useful for understanding the history of water on Mars. However, the Curiosity rover at Gale crater, Mars, has observed river deposits that are not associated with fluvial ridges, but rather bench‐ and nose‐like landforms that are not generally associated with ancient river deposits. We modified a computer model that generates fluvial ridges from ancient river deposits by adding a preferred direction for scarp retreat, which may exist in craters on Mars because crater topography steers winds, and winds currently drive erosion on Mars. Our model generated benches and noses rather than fluvial ridges, demonstrating that these landforms may be used as indicators of ancient river deposits in craters on Mars, similar to fluvial ridges. Key Points: River stratigraphy at Gale crater, Mars, is exposed along landforms distinct from the fluvial ridges commonly observed outside cratersAn erosion model with a preferential scarp‐retreat direction forms topographic benches and noses from river stratigraphy, rather than fluvial ridgesAlluvial strata in other craters on Mars may be exposed along noses and benches [ABSTRACT FROM AUTHOR]

Detecting impact craters on the Martian surface is a critical component of studying Martian geomorphology and planetary evolution. Accurately determining impact crater boundaries, which are distinguishable geomorphic units, is important work in geological and geomorphological mapping. The Martian topography is more complex than that of the Moon, making the accurate detection of impact crater boundaries challenging. Currently, most techniques concentrate on replacing impact craters with circles or points. Accurate boundaries are more challenging to identify than simple circles. Therefore, a boundary delineator for Martian crater instances (BDMCI) using fusion data is proposed. First, the optical image, digital elevation model (DEM), and slope of elevation difference after filling the DEM (called slope of EL_Diff to highlight the boundaries of craters) were used in combination. Second, a benchmark dataset with annotations for accurate impact crater boundaries was created, and sample regions were chosen using prior geospatial knowledge and an optimization strategy for the proposed BDMCI framework. Third, the multiple models were fused to train at various scales using deep learning. To repair patch junction fractures, several postprocessing methods were devised. The proposed BDMCI framework was also used to expand the catalog of Martian impact craters between 65°S and 65°N. This study provides a reference for identifying terrain features and demonstrates the potential of deep learning algorithms in planetary science research. [ABSTRACT FROM AUTHOR]

The Máaz formation consists of the first lithologies in Jezero crater analyzed by the Mars 2020 Perseverance rover. This formation, investigated from Sols (Martian days) 1 to 201 and from Sols 343 to 382, overlies the Séítah formation (previously described as an olivine‐rich cumulate) and was initially suggested to represent an igneous crater floor unit based on orbital analyses. Using SuperCam data, we conducted a detailed textural, chemical, and mineralogical analyses of the Máaz formation and the Content member of the Séítah formation. We conclude that the Máaz formation and the Content member are igneous and consist of different lava flows and/or possibly pyroclastic flows with complex textures, including vesicular and non‐vesicular rocks with different grain sizes. The Máaz formation rocks exhibit some of the lowest Mg# (=molar 100 × MgO/MgO + FeO) of all Martian igneous rocks analyzed so far (including meteorites and surface rocks) and show similar basaltic to basaltic‐andesitic compositions. Their mineralogy is dominated by Fe‐rich augite to possibly ferrosilite and plagioclase, and minor phases such as Fe‐Ti oxides and Si‐rich phases. They show a broad diversity of both compositions and textures when compared to Martian meteorites and other surface rocks. The different Máaz and Content lava or pyroclastic flows all originate from the same parental magma and/or the same magmatic system, but are not petrogenetically linked to the Séítah formation. The study of returned Máaz samples in Earth‐based laboratories will help constrain the formation of these rocks, calibrate Martian crater counting, and overall, improve our understanding of magmatism on Mars. Plain Language Summary: The Mars 2020 Perseverance rover landed on Mars in the Jezero crater on 18 February 2021. The main goals of this mission are to constrain the geology of the Jezero crater and its delta, to search for biosignatures (evidence of ancient life), to sample rocks to return to Earth, and to prepare for human exploration. Here we study the rock formation observed at the landing site, named the Máaz formation. We conclude that this rock formation is igneous (=formed from cooling and crystallization of lava or magma) consisting of iron‐rich basaltic lava flows, formed through effusive (i.e., outpouring of lava without explosions) volcanism. When compared to other Martian magmatic rocks, these rocks show a large variety of textures (shape and size of minerals) and compositions, making them different from the Martian magmatic rocks studied so far. The various lava flows of the Máaz rocks are likely all related, but not related to the underlying Séítah rock formation. Perseverance has collected core samples from the Máaz and Séítah rocks that could be among the Martian rocks to be returned to Earth in the 2030s. Their study in Earth‐based laboratories will allow us to better understand the evolution of Martian magmatism. Key Points: The Máaz formation in Jezero crater consists of basaltic to basaltic‐andesite lava flows likely originating from the same parental magmaThe Máaz formation shows various igneous textures and has a different magmatic history than the other known Martian igneous rocksThe study of samples from the Máaz formation on Earth will help constrain the Martian cratering chronology and Martian igneous evolution [ABSTRACT FROM AUTHOR]

Séítah is the stratigraphically lowest formation visited by Perseverance in the Jezero crater floor. We present the data obtained by SuperCam: texture by imagery, chemistry by Laser‐Induced Breakdown Spectroscopy, and mineralogy by Supercam Visible and Infrared reflectance and Raman spectroscopy. The Séítah formation consists of igneous, weakly altered rocks dominated by millimeter‐sized grains of olivine with the presence of low‐Ca and high‐Ca pyroxenes, and other primary minerals (e.g., plagioclase, Cr‐Fe‐Ti oxides, phosphates). Along a ∼140 m long section in Séítah, SuperCam analyses showed evidence of geochemical and mineralogical variations, from the contact with the overlying Máaz formation, going deeper in the formation. Bulk rock and olivine Mg#, grain size, olivine content increase gradually further from the contact. Along the section, olivine Mg# is not in equilibrium with the bulk rock Mg#, indicating local olivine accumulation. These observations are consistent with Séítah being the deep ultramafic member of a cumulate series derived from the fractional crystallization and slow cooling of the parent magma at depth. Possible magmatic processes and exhumation mechanisms of Séítah are discussed. Séítah rocks show some affinity with some rocks at Gusev crater, and with some Martian meteorites suggesting that such rocks are not rare on the surface of Mars. Séítah is part of the Nili Fossae regional olivine‐carbonate unit observed from orbit. Future exploration of Perseverance on the rim and outside of the crater will help determine if the observations from the crater floor can be extrapolated to the whole unit or if this unit is composed of distinct sub‐units with various origins. Plain Language Summary: The Mars 2020 Perseverance rover landed on Mars in the Jezero crater on 18 February 2021. An important goal of this mission is to constrain the geology of the Jezero crater and its delta, and to sample rocks to return to Earth. Here, we study the deepest rock formation observed close to the landing site on the crater floor, named the Séitah formation. We conclude that this formation is igneous with rocks consisting in the accumulation of dominant millimeter‐sized olivine crystals with pyroxenes and other minerals. Such rocks form at depth by slow cooling of the magma, and the first mineral to crystallize (olivine) settles down by gravity in the magma. Such rocks bear similarity to other Martian rocks found in the Gusev crater by the Opportunity rover, and also to some Martian meteorites. These rocks will be studied in Earth‐based laboratories and will allow us to better understand magmatic processes on Mars. Key Points: The Séítah formation consists of an olivine cumulate series, weakly altered, preserving the igneous texture and mineralogyEmplacement of the Séítah formation required fractional crystallization and slow cooling of the parent magma at depth and erosionThe Séítah formation could be a particular member of the Nili Fossae regional olivine‐carbonate unit observed from orbit [ABSTRACT FROM AUTHOR]

During the first year of NASA's Mars 2020 mission, Perseverance rover has investigated the dark crater floor unit of Jezero crater and four samples of this unit have been collected. The focus of this paper is to assess the potential of these samples to calibrate the crater‐based Martian chronology. We first review the previous estimation of crater‐based model age of this unit. Then, we investigate the impact crater density distribution across the floor unit. It reveals that the crater density is heterogeneous from areas which have been exposed to the bombardment during the last 3 Ga to areas very recently exposed to bombardment. It suggests a complex history of exposure to impact cratering. We also display evidence of several remnants of deposits on the top of the dark floor unit across Jezero below which the dark floor unit may have been buried. We propose the following scenario of burying/exhumation: the dark floor unit would have been initially buried below a unit that was a few tens of meters thick. This unit then gradually eroded away due to Aeolian processes from the northeast to the west, resulting in uneven exposure to impact bombardment over 3 Ga. A cratering model reproducing this scenario confirms the feasibility of this hypothesis. Due to the complexity of its exposure history, the Jezero dark crater floor unit will require additional detailed analysis to understand how the Mars 2020 mission samples of the crater floor can be used to inform the Martian cratering chronology. Plain Language Summary: Perseverance rover landed within Jezero crater (Mars) in 2021 and is collecting rocks that will be returned to Earth. In terrestrial state‐of‐the art labs, these rocks will be dated. It will allow to test the method planetary scientists are using to assess the age of Martian surfaces: their impact crater statistics. As impact craters are forming regularly, their statistics are used as a timeline in planetary sciences. The present paper studies the statistic of impacts craters within Jezero crater to reveal that the floor of Jezero has been protected from bombardment during years. These results imply that the collected rocks of the Jezero crater floor will not be ideal to test the method of using impact crater as chronometer of Martian surfaces. Key Points: The dark floor unit of the Jezero crater displays an unusual inhomogeneous crater density, suggesting a complex exhumation historyThe crater density of the dark crater floor unit corresponds to the exposure time post exhumationThe crater density of this unit will not allow the calibration of the Martian crater chronology from return samples [ABSTRACT FROM AUTHOR]

The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape‐to‐microscopic textural, mineralogical, and geochemical evidence for igneous lithologies, some possibly emplaced as lava flows. The samples contain major rock‐forming minerals such as pyroxene, olivine, and feldspar, accessory minerals including oxides and phosphates, and evidence for various degrees of aqueous activity in the form of water‐soluble salt, carbonate, sulfate, iron oxide, and iron silicate minerals. Following sample return, the compositions and ages of these variably altered igneous rocks are expected to reveal the geophysical and geochemical nature of the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. Petrographic observations and geochemical analyses, coupled with geochronology of secondary minerals, can also reveal the timing of aqueous activity as well as constrain the chemical and physical conditions of the environments in which these minerals precipitated, and the nature and composition of organic compounds preserved in association with these phases. Returned samples from these units will help constrain the crater chronology of Mars and the global evolution of the planet's interior, for understanding the processes that formed Jezero Crater floor units, and for constraining the style and duration of aqueous activity in Jezero Crater, past habitability, and cycling of organic elements in Jezero Crater. Plain Language Summary: Here we provide a narrative of sample collection and associated in situ rover observations for the rocks collected by the Perseverance rover to provide a preliminary description of the first samples of the Mars 2020 mission. These rocks collected in Jezero Crater represent the first samples from Mars with a known geologic context, the first collected with the potential to be returned to Earth for laboratory analysis, and the first cores from rock outcrops on another planet. Remote and proximal analyses indicate that all crater floor outcrops investigated are igneous in origin. Laboratory analyses of these rocks will be useful to study the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. All collected rocks have interacted with water and contain secondary geochemical and mineralogical evidence that can be used to understand aqueous environments in the crater and the potential conditions of habitability for ancient life on Mars. Key Points: Nine samples, consisting of four pairs of rock cores and a tube of atmospheric gas, were collected from the floor of Jezero Crater, MarsIn situ observations of crater floor outcrops, used as proxies for the samples, reveal aqueously altered igneous lithologiesPerseverance will leave one sample from each pair at the Three Forks depot and retain a second to be cached with future samples [ABSTRACT FROM AUTHOR]

This paper performs an analysis of aeolian activity on Herschel crater on Mars from two dune fields in different topographical settings. At East field, between small simple craters, and at West the dune field is located inside a large impact crater, near to uplifted central peak. As source of data will be employed high resolution images (spatial resolution 0.25 m/pixel) and digital terrain models (DTM), with 1m / pixel spatial resolution, generated by HiRISE sensor of orbital probe Mars Reconnaissance Orbiter (MRO). Were measured horizontal parameters (Area, Azimuth length, width, and length/width ratio) and vertical parameters (height of crest (HC), height of slipface (HS), slipface slope, curvature) of 10 dunes in each field. In Field Herschel East, it is characterized by the unimodal wind regime. They have fat and free barchans on the uphill. The evolution is for axial barchanoids, with the presence of transverse dunes. It consists of a megabarchan interrupted by an impact crater 947m in diameter. The wind shadow generated by the main impact crater stands out as a phenomenon. The dunes have little azimuth variation. Ripple marks occur in the interdune region influenced by night wind and topography. Similar conditions were identified in similar terrestrial environments such as White Sands (New Mexico), Wolfe Creek (Australia) and Lagoa da Conceição (Santa Catarina). In Herschel Field West Acute Bimodal. They present normal and thin sloping downhill dunes, some anchored in Yardangs, with lots of azimuth variation. As a terrestrial analogue, we have the Liwa Oasis (United Arab Emirates / Saudi Arabia). [ABSTRACT FROM AUTHOR]

Jezero Crater on Mars is a paleolacustrine environment where Mg-carbonates may host evidence of ancient life. To elucidate the environmental and mineralogical controls on biosignature preservation, we examined samples from five terrestrial analogs: Lake Salda (Turkey), Lake Alchichica (Mexico), Qinghai-Tibetan Plateau (China), Mg-carbonate playas (British Columbia, Canada), and a mine with fine-grained ultramafic tailings (Yukon, Canada). The mineralogical compositions of the samples varied, yet were often dominated by either aragonite (CaCO3) or hydromagnesite [Mg5(CO3)4(OH)2·4H2O]. Aragonite-rich samples from Alchichica, Mg-carbonate playas, and the ultramafic mine contained an abundance of entombed microbial biomass, including organic structures that resembled cells, whereas hydromagnesite-rich samples were devoid of microfossils. Aragonite often precipitates subaqueously where microbes thrive, thereby increasing the likelihood of biomass entombment, while hydrated Mg-carbonates typically form by evaporation in subaerial settings where biofilms are less prolific. Magnesite (MgCO3), the most stable Mg-carbonate, forms extremely slowly, which may limit the capture of biosignatures. Hydrated Mg-carbonates are prone to transformation via coupled dissolution–precipitation reactions that may expose biosignatures to degradation. Although less abundant, aragonite is commonly found in Mg-carbonate environments and is a better medium for biosignature preservation due to its fast precipitation rates and relative stability, as well as its tendency to form subaqueously and lithify. Consequently, we propose that aragonite be considered a valuable exploration target on Mars. [ABSTRACT FROM AUTHOR]

Martian ice holds an important key to interpreting Mars' past climate, but much is still unknown regarding the distribution and properties of Mars' ice deposits. Previous surveys identified craters that contain "outlying" deposits of ice separate from, but nearby, the north and south polar layered deposits (NPLD and SPLD). There are many differences between the characteristics of the NPLD and SPLD, which may or may not be shared by these outlying deposits, and may provide clues to the climate conditions under which ice in the polar regions formed. Ground penetrating radar is one of the crucial datasets for understanding Martian ice, as it can probe the subsurface and place constraints on the properties of buried materials. We have analyzed 517 SHARAD radar tracks across 24 ice deposits housed within craters, including quantifying surface reflectivity and identifying the presence of subsurface reflectors. After examining the subsurface radar observations, we determined that the northern outlier deposits share many common characteristics with the NPLD, and thus may have been emplaced concurrently or at least under similar environmental conditions. The southern outlying crater deposits exhibit a variety of subsurface characteristics, and likely represent two or more populations of ice‐rich deposits that may have differing emplacement histories. Plain Language Summary: Mars has two large ice caps at its poles, which combined contain a similar volume of ice as Greenland on Earth. Near these large ice caps are craters that are also filled with ice, referred to as outlying crater ice deposits. These outlying crater ice deposits may or may not have formed at the same time as the polar caps. Like scientists on Earth use ice cores to analyze how our climate has changed over time, radar observations of ice on Mars can penetrate deep into the ice and act as digital ice cores, recording changes to the ice deposited over time. We use these radar observations to analyze the history of the outlying crater deposits and find that the northern deposits may have had a similar history to the north polar cap, while the southern deposits may have a more varied history. Key Points: We analyzed the radar surface and subsurface properties of outlying ice deposits in craters near the Martian polesSouthern outlying deposits likely represent two or more different depositional historiesNorthern outlying deposits likely record the same depositional history as the north polar layered deposit [ABSTRACT FROM AUTHOR]

We investigated 634 crater clusters on Mars detected between 2007 and 2021, which represent more than half of all impacts discovered in this period. Crater clusters form when meteoroids in the 10 kg–10 ton mass range break up in Mars' atmosphere to produce a few to a few hundred fragments that hit the ground. The properties of the clusters can inform our understanding of meteoroid properties and the processes that govern their fragmentation. We mapped individual craters >1 m within each cluster and defined a range of cluster properties based on the spatial and size distributions of the craters. The large data set, with over eight times more cluster observations than previous work, provides a more robust statistical investigation of crater cluster parameters and their correlations. Trends in size, dispersion, and large crater fraction with elevation support weak atmospheric filtering of material. The diversity in the number of individual craters within a cluster, and their size‐frequency distributions, may reflect either a diversity in fragmentation style, fragility, or internal particle sizes. Plain Language Summary: Between 2007 and 2021, over a thousand newly formed impact craters have been detected on the surface of Mars. Over half are from bodies that have broken up in the atmosphere, forming clusters of craters. We have mapped all the individual craters in each of these clustered impact sites. By investigating the properties of these sites, such as how many individual craters are there, their dispersion and their size, we can improve our understanding of the impacting bodies and how they break up. We find a wide diversity of cluster patterns, with some elevation dependence. This suggests that, although the atmosphere plays a role in meteoroid break up, there is great variety in the impactor bodies themselves. Key Points: Crater cluster properties inform our understanding of meteoroid fragmentationAtmospheric influence reflected in crater cluster properties varies with elevationSize‐frequency crater distribution in clusters suggests larger impactors are weaker in bulk strength [ABSTRACT FROM AUTHOR]

Seismic activity generated by impacts depends on impact conditions and properties of the impact site. Here, we combined mapping of the regolith thickness with numerical impact simulations to better estimate the seismic efficiency and seismic moment generated in small impact events in the uppermost crust on Mars. We used mapping of crater morphology to determine the regolith thickness that craters formed in. We found that local regolith thickness in the late Amazonian units is between 4 and 9 m. Combined with previous estimates for the NASA InSight landing site, we composed a more realistic uppermost crust analog and implemented it in numerical impact simulations. We estimated the seismic efficiency and seismic moment for small craters on Mars impacting a non‐porous or fractured bedrock overlaid by 5, 10, or 15 m thick regolith. Seismic energy showed more dependence on target properties. Three orders of magnitude more energy were produced in stronger targets. The seismic moment does not depend on target properties, and we confirm that seismic moment is almost proportional to impact momentum. The resulting seismic moment is in agreement up to a factor of 4 between different target types. We improved the scaling relationships developed from numerical simulations used in seismic moment approximations by constraining its dependence on more realistic target properties. Plain Language Summary: Small impacts form in the top few meters of the crust of Mars. From the NASA InSight mission data, we learned that the uppermost crust of Mars is layered. Here, we mapped and used rocky ejecta craters as a proxy to estimate the thickness of this top layer. We demonstrated that a younger, late Amazonian geological unit, has a thinner top regolith layer (4–9 m) compared to an older, Hesperian unit (3–17 m). We modeled several target scenarios, constrained by mapping results, and performed a suite of numerical simulations of small impacts. From these simulations, we determined a relationship between impact‐generated seismic energy and the seismic moment for different types of Martian upper‐crust analogs. Our models show that impact‐generated seismic energy strongly depends on target properties (three orders of difference among different analogs investigated here). On the contrary, seismic moment shows agreement up to a factor of 4 in different targets. We discussed our modeling results to the newly detected impacts on Mars, and confirmed that our models are reliable for predicting seismic moments of small impacts. Our results contribute to the understanding of the size and energy of impact‐generated seismic sources in different target analogs. Key Points: Using rocky ejecta craters, we mapped regolith thickness on Mars and found that in the late Amazonian volcanic unit, it is 4–9 mSeismic efficiency shows larger sensitivity on target properties (up to three orders of magnitude) than the seismic moment (factor of four)A comparison of numerical simulations with the new seismic detections of craters on Mars showed agreement with our models [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The goals of NASA's Mars 2020 mission include searching for evidence of ancient life on Mars, studying the geology of Jezero crater, understanding Mars' current and past climate, and preparing for human exploration of Mars. During the mission's first science campaign, the Perseverance rover's SHERLOC deep UV Raman and fluorescence instrument collected microscale, two‐dimensional Raman and fluorescence images on 10 natural (unabraded) and abraded targets on two different Jezero crater floor units: Séítah and Máaz. We report SHERLOC Raman measurements collected during the Crater Floor Campaign and discuss their implications regarding the origin and history of Séítah and Máaz. The data support the conclusion that Séítah and Máaz are mineralogically distinct igneous units with complex aqueous alteration histories and suggest that the Jezero crater floor once hosted an environment capable of supporting microbial life and preserving evidence of that life, if it existed. Plain Language Summary: The goals of NASA's Mars 2020 mission include searching for evidence of ancient life on Mars, studying the geology of Jezero crater, understanding Mars' current and past climate, and preparing for human exploration of Mars. During the mission's first science campaign, SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), one of Perseverance rover's spectroscopic instruments, collected microscale, two‐dimensional images that displayed mineral and organic molecule detections on 10 natural (unabraded) and abraded targets on two different Jezero crater floor geological units: Séítah and Máaz. We report SHERLOC mineral detections made during the Crater Floor Campaign and discuss their implications regarding the origin and history of Séítah and Máaz. The mineral detections support the conclusion that Séítah and Máaz are igneous units with different mineral compositions and distinct histories of alteration by fluids. The detections further suggest that the Jezero crater floor was once home to an environment capable of supporting microbial life and preserving evidence of that life, if it ever existed. Key Points: The floor of the Jezero crater hosts distinct igneous units with differing aqueous alteration historiesSHERLOC Raman mineral class detections indicate that the Jezero crater floor was once a habitable environmentSome Crater Floor Campaign samples may contain salts known to preserve biosignatures in terrestrial analog environments [ABSTRACT FROM AUTHOR]

Hydromagnesite Mg5CO34(OH)2⋅4H2O $\left({\mathsf{M}\mathsf{g}}_{5}{\left({\mathsf{C}\mathsf{O}}_{3}\right)}_{4}{(\mathsf{O}\mathsf{H})}_{2}\cdot 4{\mathsf{H}}_{2}\mathsf{O}\right)$ is a common hydrated magnesium carbonate mineral found in alkaline lakes on Earth, potentially present on Mars, and is also a key mineral for carbon capture and storage. However, mechanisms governing its formation in alkaline lakes remain enigmatic. Extensive hydromagnesite formed during the Holocene in the alkaline Dujiali Lake (DL), central Qinghai‐Tibetan Plateau, making it an ideal field site to constrain the process of hydromagnesite formation in a modern environmental context. In this study, we report a set of magnesium isotope ratios (Mg26/Mg24 ${}^{26}\mathsf{M}\mathsf{g}/{}^{24}\mathsf{M}\mathsf{g}$ expressed as δ26 Mg) data from DL on abiotic hydromagnesite (mean = −1.35‰ ± 0.14‰) modern lake waters (−0.07‰ to +0.46‰), and rivers and groundwater (−0.53‰ to −1.46‰). These differences in δ26 Mg (and also Mg/Ca) are most likely caused by low‐Mg carbonate precipitation, a process which fractionates Mg/Ca and δMg26 $\delta {}^{26}\mathsf{M}\mathsf{g}$ values. A semi‐quantitative box model of the lake chemistry was developed based on carbonate equilibria to investigate the behavior of Mg isotopes during the evolution of the lake chemistry. The modeling results indicate that evaporation concentrates solutes in the lake driving saturation of multiple minerals. Aragonite reaches saturation before hydromagnesite, preferentially removing Ca relative to Mg via aragonite precipitation. This process elevates the Mg/Ca of the lake and the saturation index of hydromagnesite, increasing the likelihood of hydromagnesite formation. Given that the Mg/Ca ratio of many alkaline lakes is far below than that required for the formation of hydromagnesite, our findings suggest that low‐Mg carbonate precipitation may be a common precursor process for abiotic hydromagnesite precipitation in evaporative environments in addition to a high Mg source likely derived from ultramafic rocks. Plain Language Summary: Hydromagnesite Mg5CO34(OH)2⋅4H2O $\left({\mathsf{M}\mathsf{g}}_{5}{\left({\mathsf{C}\mathsf{O}}_{3}\right)}_{4}{(\mathsf{O}\mathsf{H})}_{2}\cdot 4{\mathsf{H}}_{2}\mathsf{O}\right)$ is a common hydrated magnesium carbonate mineral on the Earth and is suspected to be present at the Jezero Crater on Mars. Hydromagnesite formation requires high Mg/Ca ratios, typically associated with the weathering of ultramafic rocks. However, the Mg/Ca ratios of the input waters associated with ultramafic rocks in most of the settings are seldom high enough for hydromagnesite precipitation in alkaline lakes. Our study suggests that although ultramafic Mg source rocks are important for hydromagnesite precipitation, the removal of Ca through Ca‐carbonate formation is an essential precursor process for increasing the Mg/Ca ratio under intense evaporation conditions to induce spontaneous hydromagnesite precipitation. Key Points: New Mg isotope data on Holocene hydromagnesite, modern lake, and river waters from the alpine Dujiali Lake, central Qinghai‐Tibetan PlateauA thermodynamic based box model simulates the behavior of the carbonate system and Mg isotopes during the evolution of the lake chemistryLow‐Mg carbonate precipitation may be a common precursor process for driving hydromagnesite precipitation in evaporative alkaline lakes [ABSTRACT FROM AUTHOR]

Water ice in the Martian mid‐latitudes has advanced and retreated in response to variations in the planet's orbit, obliquity, and climate. A 150 m‐diameter new impact crater near 35°N provides the lowest‐latitude impact exposure of subsurface ice on Mars. This is the largest known ice‐exposing crater and provides key constraints on Martian climate history. This crater indicates a regional, relatively pure ice deposit that is unstable and has nearly vanished. In the past, this deposit may have been tens of meters thick and extended equatorward of 35°N. We infer that it is overlain by pore ice emplaced during temporary stable intervals, due to recent climate variability. The marginal survival of ice here suggests that it is near the edge of shallow ice that regularly exchanges with the atmosphere. Plain Language Summary: A 150 m‐diameter new impact crater on Mars exposes water ice, constraining the nature of past and present ice sheets and paleoclimate. The past climate has varied, gradually removing a massive ice deposit that has nearly been lost at 35°N but survives at higher latitude. Key Points: Water ice is exposed in a 150 m‐diameter new impact crater near 35°N on MarsThe ice includes both massive ice and a covering layer of pore iceThis ice marks the southern margin of remaining ice deposits from high‐obliquity periods [ABSTRACT FROM AUTHOR]

Crater recognition on Mars is of paramount importance for many space science applications, such as accurate planetary surface age dating and geological mapping. Such recognition is achieved by means of various image-processing techniques employing traditional CNNs (convolutional neural networks), which typically suffer from slow convergence and relatively low accuracy. In this paper, we propose a novel CNN, referred to as MC-UNet (Martian Crater U-Net), wherein classical U-Net is employed as the backbone for accurate identification of Martian craters at semantic and instance levels from thermal-emission-imaging-system (THEMIS) daytime infrared images. Compared with classical U-Net, the depth of the layers of MC-UNet is expanded to six, while the maximum number of channels is decreased to one-fourth, thereby making the proposed CNN-based architecture computationally efficient while maintaining a high recognition rate of impact craters on Mars. For enhancing the operation of MC-UNet, we adopt average pooling and embed channel attention into the skip-connection process between the encoder and decoder layers at the same network depth so that large-sized Martian craters can be more accurately recognized. The proposed MC-UNet is adequately trained using 2∼32 km radii Martian craters from THEMIS daytime infrared annotated images. For the predicted Martian crater rim pixels, template matching is subsequently used to recognize Martian craters at the instance level. The experimental results indicate that MC-UNet has the potential to recognize Martian craters with a maximum radius of 31.28 km (136 pixels) with a recall of 0.7916 and F 1 -score of 0.8355. The promising performance shows that the proposed MC-UNet is on par with or even better than other classical CNN architectures, such as U-Net and Crater U-Net. [ABSTRACT FROM AUTHOR]

Martian meteorites represent the only samples of Mars available for study in terrestrial laboratories. In addition to their crystallization and surface ejection ages, these samples provide a detailed understanding of the geochemistry of the martian crust. One of the major outstanding problems regarding martian meteorites is locating the exact source regions on Mars, although the composition and texture of these meteorites limits the source craters to mostly igneous provinces. To help find source craters, we present an updated global catalog of impact craters greater than 3 km diameter with thermally distinct radial patterns ("rays"), which could represent recent impact events. We defined search criteria for identifying rayed craters, assigning a confidence level to each crater, and noted the presence or absence of associated secondary craters. Using daytime and nighttime thermal infrared image data we identified 118 craters with thermally distinct radial patterns between ±60° latitude, of which 89 had not appeared in previous catalogs. We discuss some potential uses of this new catalog in terms of understanding the morphology, location, and composition of each crater. Our preliminary analysis demonstrates the potential future use of this catalog in finding the source location of martian meteorites in regions of sufficient thermal contrast. Plain Language Summary: At present, the only rock samples we have of Mars come from meteorites. These rocks were thrown off the surface of Mars by large meteorite impacts, with enough energy to allow some material to escape and eventually cross the orbit of Earth. These samples tell us much about the geological history of Mars, but it is difficult to know exactly where they come from on the surface. Finding the source location is essential to complete the picture of how these rocks formed, and how Mars evolved. To help find the source location, we have created an updated catalog of craters on Mars that have a distinctive radial pattern, which may disappear relatively quickly on geological timescales. These rayed craters likely represent recent large impacts that could match the young ejection ages (less than about 20 million years) of the martian meteorites. We explore the potential problems of identifying such features, but explore some possible uses in comparing global data sets from Mars with laboratory data of the meteorites. We also identify some interesting craters that are worthy of future detailed studies as possible sources of martian meteorites. Key Points: New global catalog of 118 rayed craters on MarsDemonstrate the potential use in studies of martian meteorite source locationMorphology and model surface ages support recent impact of rayed craters [ABSTRACT FROM AUTHOR]

The Perseverance rover, Mars 2020 mission, landed on the surface of the Jezero crater, on 18 February 2021. This Martian crater is suspected to have hosted a paleolake as evidenced by the numerous detections of aqueously altered phases and thus is a promising candidate for the search for past Martian life. The SuperCam instrument, a collaboration by a consortium of American and European laboratories, plays a leading role in this investigation, thanks to its highly versatile payload providing rapid, synergistic, fine‐scale mineralogy, chemistry, and color imaging. After its landing, the first measurements of Martian targets with the infrared spectrometer of SuperCam (IRS) showed new instrumental behaviors that had to be characterized and calibrated to derive unbiased science data. The IRS radiometric response has thus been calibrated using periodic observations of the Aluwhite SuperCam Calibration Target (SCCT). Parasitic effects were understood and mitigated, and the instrumental dark and noise are characterized and modeled. The reflectance calibrated data products, provided periodically on the NASA Planetary Data System, are corrected for the main instrumental features. This radiometric calibration allowed us to study the 2.5 μm absorption band, which has been discovered in the Séítah unit and is associated with phyllosilicates‐carbonates mixtures. Plain Language Summary: This paper is an instrumental investigation of the infrared spectrometer (IRS) portion of the SuperCam instrument on the Mars Science Laboratory Perseverance rover. Work performed prior to and during flight operations enabled the derivation of a proper instrumental response suitable for calibration of infrared point spectra of rocks and soils observed along the rover traverse. The paper describes development of a full data reduction pipeline in which the radiometric response, sensitivity of the IRS electronic board to temperature, and electromagnetic interference artifacts were removed. A companion paper (Mandon et al., 2022, https://doi.org/10.1029/2022JE007450) investigates the IRS data set through Sol 379 in more detail. Here, we specifically explore the 2.5 μm band attributed to carbonates in Séítah unit's phyllosilicate‐carbonates mixtures. We found that such mixtures likely have a low carbonate content, which may indicate low amounts of chemical alteration or an alteration by a carbon‐poor fluid. Key Points: The infrared spectrometer of SuperCam on Perseverance has been successfully flight calibrated using the onboard calibration targetsCalibration permitted to study the most challenging long wavelengths and thus to discover an absorption band at 2.5 μmStudy of the 2.3 and 2.5 μm absorption bands showed the Séitah unit has variable clay and carbonate mixtures with low carbonate content [ABSTRACT FROM AUTHOR]

The ancient surface of Mars is dominated by degraded impact craters with reduced or eliminated rim relief. Some degraded craters have an inlet valley, while many remain fluvially isolated. Despite controlling Martian fluvial connectivity, few constraints exist on why some—but not all—degraded craters possess inlets. We compared a suite of properties around degraded Martian craters with and without inlets to ascertain what topographic and hydrologic factors influenced inlet formation. Slope and surface roughness are similar, but topographic inset within the catchment, drainage density, and potential contributing areas diverge for breached and non‐breached craters. We suggest that the importance of basin hydrology‐related factors over topographic factors is the result of the former less frequently surpassing inlet incision thresholds than the latter. We conclude that greater topographic inset (i.e., craters deeper within regional depressions) promoted higher discharge, and that inlet valley formation was ultimately controlled by Mars' crater‐dominated topography. Plain Language Summary: The ancient surface of Mars is dominated by impact craters that have been modified by mass wasting, aeolian infilling, water activity, and subsequent impact cratering. Erosion has lowered or eliminated the relief of many craters' rims, resulting in "degraded" craters. On early Mars, water activity also led to the formation of branching valley networks, which flow into some Martian impact craters. However, many degraded craters remain without an inlet valley. Inlet formation reveals that water activity could overcome the disruption of topography caused by impact crater formation. Yet, little is known about factors that would promote or limit inlet valley formation and it is unclear why some—but not all—degraded craters were breached by inlet valleys on Mars. We compared a suite of properties around degraded Martian craters with and without inlets to find out what topographic (e.g., slope) and hydrologic factors (e.g., the number of valleys per area) affected inlet formation. We find that hydrology‐related factors are very different between craters with and without inlets, while topographic factors are similar. Our results suggest that inlet valley formation was ultimately controlled by hydrologic routing on Mars' crater‐dominated surface. Key Points: We compared slope, roughness, drainage density, and catchment geometry around degraded Martian craters with and without an inlet valleyOnly relative topographic inset, drainage density, and potential contributing area differ between the breached and non‐breached subsetWe conclude that more inset craters (i.e., deeper or more central in a basin) received greater discharge which promoted inlet breaching [ABSTRACT FROM AUTHOR]

S1094b is the largest (155 m-size) and southernmost known ice-exposing fresh crater discovered so far on Mars, revealing a relatively pure and unstable subsurface ice deposit located at the northern Martian mid-latitudes. In this work, we analyze HiRISE images taken on 27 February 2022 and on 5 December 2022 to perform a multi-temporal analysis of its ice-rich ejecta, combining this analysis with geologic mapping, the boulder size frequency distribution (SFD) and thermal modeling. The objective is to provide a multidisciplinary characterization of both the impact and subsequent exposed ice sublimation processes. The boulder SFD of both February and December cases show a power-law best fit with indices −4.68 ± 0.15 and − 3.47 ± 0.10, respectively. In the same timeframe, the density of boulders per km2 ≥ 1.5 m changes from 3908, to 596. This flattening is mainly due to the sublimation and consequent loss of the smaller-size icy boulders. This is confirmed by the ice volume computation performed on the area, which changed from ∼20,274 ± 3997 m3 to ∼7951 ± 1117 m3, i.e. a decrease of ∼60% in 274 Sols. The thermal models showed that the ice in this region is always unstable, leading to a total of 6504.71 sublimation hours from which we estimated a sublimation rate of ∼0.15 ± 0.04 mm/h (i.e. ∼3.60 ± 0.96 mm/Sol). The presence of this amount of accessible ice at such low latitudes could be a valuable resource for potential future human missions. • Conduction of multitemporal, multidisciplinary analyses on Martian crater S1094b. • Preparation of a geological mapping 5 geologic units and 4 landforms. • Observation of sublimation focusing on the smallest icy boulders loss. • Detection of the 60% water ice sublimation over 281 days. • Average sublimation rate detected at ∼1.96 m3/h or ∼ 0.15 ± 0.04 mm/h. [ABSTRACT FROM AUTHOR]

The multiple-layered ejecta surrounding crater Kotka (east of Elysium Mons) are studied using imagery and physical modelling. This particular crater was chosen not only because its ejecta are well preserved, but more importantly because the impact area is surrounded by mounds, which provide a means of determining the velocity of the ejecta based on run-up criteria. If the ejecta passed over a mound of a certain height, the velocity was greater than that necessary to rise up that height, while the presence of a shadow beyond the mound indicates a velocity lower than that limit. Top ejecta flow velocities were found to vary between 25 m/s and 80 m/s. Velocities are also determined based on the length of the jump against craters rims, a criterion that provides an estimate of the velocity, rather than a limit, and are found to be compatible with those estimated with run-up criteria. We find that a first train of ejecta travelling at high velocity was capable of overcoming many mounds. A peculiar rampart often visible at the foot of many of the mounds is interpreted as a frozen hydraulic jump indicating a phase in which the ejecta were about to stop. The velocity of the ejecta was found to decrease with distance from the rim but not as fast as a constant friction model would suggest, indicating effective friction that increases with distance, and more complex rheology than pure frictional behavior. The velocities indicate a rheology for the fluidized ejecta in which the debris material was completely fluidized, to the point that the friction coefficient decreased by one to two orders of magnitude compared to the one of fragmented rock. Our conceptual model is that the ejecta material initially contained a large amount of solid ice that was fluidized and vaporized by the impact. The chains of pits visible in the ejecta, interpreted as fossilized bubbles of volatiles released through the hot fluidized material, confirm that high temperatures were reached during impact, as also indicated by analytical estimates. Fluidization altered the rheology of the ejecta in a way that has yet to be understood. • The run-ups on mounds of ejecta surrounding the multiple-layered ejecta crater Kotka on Mars are studied. • Velocities estimated on mounds an with leaps lengths along craters are found in the range 25–80 m/s. • The dynamics indicate initial fluidized phase due to hot vapor followed by frictional behavior of ejecta. [ABSTRACT FROM AUTHOR]

Ejecta blankets around craters on a km-scale show stark differences in the ejecta mobility (maximal extent of ejecta divided by the crater radius) with latitude and types of plains on Mars, which has been known for a long time (Barlow and Pollak, 2002; Li et al., 2015) but is not well-understood. Our main goal is to explore the idea that the subsurface rheology drives ejecta dynamics and leaves characteristic, observable imprints in the spatial distributions of ejecta. We conduct numerical simulations of impact cratering into a variety of subsurface models and study the impact of varied subsurface material (porous basalt, water ice, water), as well as structure and layering on impact sites and properties of impact ejecta. Our models consider variations in the depth of water or ice covering basalt; the thickness of buried ice; and the depth of burial of ice. We find that ejection angles and velocities depend on these quantities and configurations, e.g. velocities decrease and angles of ejection increase with increasing water layer thickness, buried ice thickness, or thickness of basaltic debris over an ice sheet. As a result, several ejecta characteristics derived from ejecta thickness profiles carry information about the underlying rheology. Specifically, the ejecta mobility, as well as the radial position of the maximum and the slope of the ejecta thickness profiles are diagnostic. The power-law function of the thickness profile of the ejecta blanket right after formation is a good indicator of ejecta from water- or ice-covered targets but not from more complex multi-layered structures, hence we caution against using scaling relations to describe ejecta from such targets. As any surface water/ice volatile mass is unstable on Mars, we also consider the geomorphology of craters and ejecta after the loss of volatiles. Our main findings include the observation that after the loss of surface volatiles, craters which formed in water-covered targets would appear shallower than those formed in basalt. The ejecta mobilities observed today would also be smaller if craters formed in volatile-covered targets than in basalt. Our findings can aid the interpretation of data returned from cameras onboard multiple spacecraft orbiting Mars such as HiRISE, CaSSIS, or CTX, and constitute a proof of concept of the hypothesis that information on the subsurface, including where ice is or was present, is encoded in the ejecta profile and spatial distribution. • Ejecta blankets around km-scale craters are sensitive to subsurface rheology. • Ejection velocities and angles depend on the layering of basalt and water/ice. • Post-sublimation ejecta from volatile-rich subsurfaces are smaller than from basalt. • Craters in volatile-covered targets sublime & become shallower than those in basalt. • These differences can be resolved by spacecraft imaging systems. [ABSTRACT FROM AUTHOR]

The Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) imaged two newly formed impact craters on the South Polar Layered Deposits (SPLD) of Mars in 2018 and 2020. These two new craters, the first detected on the SPLD, measure ∼17 m and ∼48 m in diameter. Follow-up observations were conducted with the High Resolution Imaging Science Experiment (HiRISE), showing seasonal and interannual changes, and providing stereo coverage for the production of digital terrain models (DTMs). Mars Climate Sounder (MCS) data were obtained over the region of these new impacts, giving surface temperature information for the time interval before and after the impacts were detected. Taken together, the optical and infrared observations of these sites reveal craters largely consistent with the morphologies of other small, dated impact craters on Mars, and crater ejecta patterns that suggest a more dust/regolith-dominated upper few meters of the SPLD in contrast to mid-latitude buried ice and lobate debris aprons (LDAs). This supports previous conclusions that the SPLD may have an upper surface depleted in water ice relative to the North PLDs, possibly the result of a widespread deflation event. • 17- and 48-m diameter new (formed 2018–2020) craters were found on the South Polar Layered Deposits. • These new craters are morphologically similar to <100 m craters elsewhere on Mars. • Ejecta composition suggests the SPLD's upper meters differ from midlatitude ices. [ABSTRACT FROM AUTHOR]

The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigated the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We found that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multistage cooling of a thick magma body. [ABSTRACT FROM AUTHOR]

Boulder‐sized clasts are common on the surface of Mars, and many are sufficiently large to be resolved by the high resolution imaging science experiment (HiRISE) camera aboard the Mars reconnaissance orbiter. The size, number, and location of boulders on the surface and their spatial distribution can reveal the processes that have operated on the surface, including boulder erosion, burial, impact excavation, and other mechanisms of boulder transport and generation. However, quantitative analysis of statistically significant boulder populations, which could inform these processes, entails prohibitively laborious manual segmentation, granulometry, and morphometry measurements over large areas. Here, we develop, describe, and validate an automated tool to locate and measure boulders on the Martian surface: the Martian Boulder Automatic Recognition System (MBARS). Our open‐source Python‐based toolkit automatically measures boulder diameter and height in HiRISE images enabling rapid and accurate assessments of boulder populations. We compare our algorithm with existing boulder‐counting methods, manual analyses, and objects of known size to verify accuracy and precision. Additionally, we test how MBARS quantitatively characterizes boulders around an impact crater in the Martian northern lowlands. We compare this to previous work on rock excavation during impact cratering using manually counted boulders around lunar craters. Plain Language Summary: Large boulders (>1 m diameter) are widely distributed on the Martian surface. They are easily observed from orbit, making them visible with high‐resolution imaging. Mapping the location, number, and size of boulders is helpful for understanding which geological processes bring boulders to the surface, move them around, and fragment them into smaller rocks and soil. Here, we describe and validate the Martian Boulder Automatic Recognition System (MBARS), a set of tools that automatically locates and measures boulders in high‐resolution images of the Martian surface. We compare results generated by MBARS with results from other automated boulder‐measuring tools as well as with results from manual boulder measurements to ensure accuracy. We also use MBARS to map boulders around an impact crater on Mars and compare the boulder distribution to a similar‐sized crater on the Moon. Key Points: The Martian Boulder Automatic Recognition System (MBARS) is a new tool to detect and measure boulders on the Martian surfaceMBARS is comparably or more accurate than prior published algorithms that measure bouldersMBARS readily reproduces manually measured results [ABSTRACT FROM AUTHOR]