Search

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]

Earth‐based telescopes and Mars‐orbiting spacecraft have revealed Mars to be a dynamic body with periodic changes spanning hours to years, and other changes that present no discernible pattern. Understanding these surface and atmospheric variations requires observing and tracking them, and that requires global, consistent image data that spans several years. In support of that goal, the Mars Orbiter Camera Wide Angle "daily global map" images, in both red and blue, have undergone a modern processing with photometric corrections. They have been projected and blended into equirectangular and polar stereographic monochromatic and synthetic three‐color mosaics in intervals of 1 day and ΔLs = 2°, 5°, 10° (approximately 4 days, 10 days, and 2.5 weeks, respectively). The full data set presents three dimensions of Mars—location, time, and color—while ranges or values within each dimension can be combined in different ways, presenting a highly complex interplay for exploration. In this work, the methods to generate the data are presented along with an overview of the data set. In the companion paper (Robbins, 2023a, https://doi.org/10.1029/2022JE007621), several new observations are made along with replication of known, previously described phenomena. Plain Language Summary: Earth today is under constant monitoring by satellites, providing views of our dynamic world. The data collected range from visible wavelengths of light we can see with our eyes to other light such as infrared and ultraviolet. This global data set gives researchers an unprecedented way to understand our dynamic planet and, for the last roughly two decades, we have been able to do the same at Mars. The first modern craft to orbit Mars was NASA's Mars Global Surveyor, which had the Mars Orbiter Camera. A wide‐angle component of that camera took red‐ and blue‐color images globally and daily during the camera's lifetime, from 1999 through 2006. That data set has been reprocessed with more recent software, mosaicked, and grouped into several different time intervals for different types of scientific investigations. Additionally, synthetic green images were created which allow approximate true‐color views of what Mars looked like during the seven Earth years that data were taken. The data reveal a dynamic world of huge cloud systems, changing surface dust patterns, seasonal changes in frost and ice cover, and vast polar cloud systems as each hemisphere slips into winter. Key Points: Mars' resolved, approximate red and blue reflectivity was derived for Earth years 1999–2006 using Mars Orbiter Camera Wide‐Angle imagesDaily, ΔLs = 2°, 5°, and 10° mosaics and synthetic three‐color composites in equirectangular, north, and south polar projections were madeThe data show a dynamic planet with seasonal patterns and secular changes to surface reflectivity, color, clouds, and ice [ABSTRACT FROM AUTHOR]

This study investigates the mineralogical, elemental, and spatial variability from source (proximal) to sink (distal) of Merapi basalt‐andesitic stratovolcano (Java, Indonesia) to better constrain volcaniclastic mineral sorting in fluvial, aeolian, and coastal environments. Merapi volcaniclastics are products of an active volcano with an ongoing quadrennial eruption, which can provide insights to constrain Mars' older and more recent volcaniclastics by focusing on anorthite, albite, and pyroxenes found on Mars' surface. We collected stream sediment samples across the Opak River that connects Merapi with the Indian Ocean. In addition to grain size analysis, all collected samples were subjected to X‐ray diffractometer and X‐ray fluorescence to quantify their mineralogical and elemental composition, respectively, like the CHEMIN instrument used by the Curiosity rover on Mars to investigate the geochemistry and mineralogy of geological units in Gale crater. Implementation of multivariate statistical analysis based on principal component analysis and Hierarchical Clustering of Principal Component are able to discriminate between fluvial, fluvio‐coastal‐aeolian, and marine influenced deposits. The quantitative assessment shows that the dominant mineralogy is influenced by pyroclastic materials dominated by plagioclase feldspars (albite and anorthite), followed by pyroxenes (augite and enstatite). Alteration modeling of Merapi samples favors a fluvial depositional environment rather than mass‐wasting from the crater rim for Gale crater rocks (i.e., Pahrump Hills, Hartmann's Valley, Karasburg, Sutton Island member) on Mars. Plain Language Summary: This research provides a detailed characterization of stream samples and surface deposits from the Opak River, the Parangkusumo Shoreface, and parabolic coastal sand dunes from an active Merapi stratovolcano (Java, Indonesia) transported from the source toward the sink. The paper aims to constrain pyroclastic mineral sorting from a basaltic to basalt‐andesitic volcanic origin throughout fluvial, coastal, and wind‐driven (aeolian) environments. We use similar methods as the MSL (Mars Science Laboratory) Team to investigate mineral sorting of volcaniclastic sediments in Gale Crater, specifically using X‐Ray spectroscopy collected by CheMin. The results of our research suggest that mineralogical sorting occurs throughout the depositional subenvironments, and they are related to the geomorphology of the river. Furthermore, the aeolian environment provides an additional sorting mechanism for the sand grains deposited in the shoreface. We also discovered a similar weathering trend of Merapi volcanic sediments with the findings from Stimson and Murray formation in Gale Crater, which supports their origin as sediment transported by the river during the wet phase of Mars. Key Points: Volcanic cyclic eruption, fluvial discharge, longshore current, and coastal volcaniclastic aeolian sand dunes are all interconnected from shaping the geomorphology of a reworked volcaniclastic terrain in Merapi sedimentary systemsMineral sorting variability can be observed in sedimentary bedforms and is strongly controlled by grain sizeChemical alteration index supports the hypotheses of Gale Crater's ancient aeolian Stimson formation and aqueous‐driven alteration of Murray formation on Mars [ABSTRACT FROM AUTHOR]

In this paper, we present the results obtained in the determination of the true north direction on Mars by using a gnomon on the InSight mission and compare the measurements with either the North determination from the Inertial Measurement Unit and imaging analysis. The obtained measurement has been used to populate the SEIS orientation information in the archived SEIS data. Images taken during December 2018 and January 2019 allow to determine the gnomon shadow position and length over a target. By calculating the Sun local coordinates using planetary ephemeris VSOP87, the images are used to estimate the true North direction on the landing site. By using eight different images selected, we obtain the true North direction with an accuracy up to 2.5°, which is confirmed by the IMU and imaging analysis. The true North direction is also confirmed by an image taken near local noon, when the sun crosses the meridian. The North determination precision is then discussed in view of the seismic determination of the back azimuth. Key Points: True North on Mars has been found using a sundial during the InSight missionThis reference direction is used for Marsquakes location [ABSTRACT FROM AUTHOR]

Surface heterogeneities below the spatial resolution of thermal infrared (TIR) instruments result in anisothermality and can produce emissivity spectra with negative slopes toward longer wavelengths. Sloped spectra arise from an incorrect assumption of either a uniform surface temperature or a maximum emissivity during the temperature‐emissivity separation of radiance data. Surface roughness and lateral mixing of different sub‐pixel surface units result in distinct spectral slopes with magnitudes proportional to the degree of temperature mixing. Routine Off‐nadir Targeted Observations (ROTO) of the Thermal Emission Imaging Spectrometer (THEMIS) are used here for the first time to investigate anisothermality below the spatial resolution of THEMIS. The southern flank of Apollinaris Mons and regions within the Medusae Fossae Formation are studied using THEMIS ROTO data acquired just after local sunset. We observe a range of sloped TIR emission spectra dependent on the magnitude of temperature differences within a THEMIS pixel. Spectral slopes and wavelength‐dependent brightness temperature differences are forward‐modeled for a series of two‐component surfaces of varying thermal inertia values. Our results imply that differing relative proportions of rocky and unconsolidated surface units are observed at each ROTO viewing geometry and suggest a local rock abundance six times greater than published results that rely on nadir data. High‐resolution visible images of these regions indicate a mixture of surface units from boulders to dunes, providing credence to the model. Plain Language Summary: Orbital thermal infrared (TIR) spectral and temperature data are used to determine numerous planetary surface properties, providing insight into how the planet's surface has evolved. This paper applies a new methodology to examine temperature mixing of surfaces with different units and particle sizes (i.e., rock and dust). Using the Thermal Emission Imaging Spectrometer (THEMIS) TIR data at 100 m/pixel, we model emissivity spectra and surface temperature to derive the abundance of these different surface units. TIR spectra are sensitive to sub‐pixel temperature differences at small scales. Surfaces with various components heat and cool at differing rates creating temperature differences within each pixel. The extracted TIR spectra will have a negative slope proportional to the degree of the temperature difference. Using a series of post‐sunset TIR images from different viewing angles, we model the surface temperature and spectral slope to derive the percent of surface units present. Matching these results to our observations allows for determining each component's particle size and abundance. Additionally, this method creates a thermophysical model that predicts a rock abundance six times greater than models derived from nadir viewing observations. This is critical for understanding modern surface evolution and future exploration, such as landing site selection. Key Points: Using Routine Off‐nadir Targeted Observations (ROTOs) of Mars Odyssey, we acquire directional thermal infrared (TIR) spectra of the surfaceTIR spectral slopes from the ROTO data enable extraction of sub‐pixel anisothermal heterogeneities at fine spatial scalesA thermal inertia mixing model is used to quantify sub‐pixel temperature mixing produced by a checkerboard mixing of surface units [ABSTRACT FROM AUTHOR]

The Mars 2020 rover, Perseverance, landed in Jezero crater (18.4663°N, 77.4298°E) on February 18, 2021 to collect samples from Mars that could be returned to Earth by a future Mars Sample Return campaign. While providing a rich sampling opportunity, Jezero also contains numerous landing hazards including scarps, canyons, mesas, dune fields, rock fields, and smaller craters. The Mars 2020 onboard inertial navigation system, which is the same as that used by the Mars Science Laboratory (MSL), only provides a very coarse inertially propagated position, which can have error as large as 3.2 km. The Lander Vision System (LVS) was added to Mars 2020 to reduce this position knowledge error to less than 40 m with respect to an on‐board reference map of the landing area. LVS uses a reference map on board to compare with the descent images for lander localization during the terminal stage of Entry, Descent and Landing (EDL). Because the reference map is used directly during EDL, it is critical that it have as little spatial and photometric error as possible. Photometrically, it should resemble as much as possible the real descent images to allow reliable terrain matching. Spatially, it should match as faithfully as possible the real, underlying terrain and contribute minimal error to the final localization solution. On February 18, 2021, the LVS reference map passed its ultimate test. The LVS system executed Terrain Relative Navigation (TRN) flawlessly based on the LVS reference map. In addition to its use for TRN, the local hazard map is also registered to the LVS reference map so that the safe target selection (STS) system can select a safe and reachable landing site. The final error between the site targeted by the STS system and the real landing site is estimated at only 5 m. The exceptional performance of LVS indicates that the reference map met mission requirements with comfortable margin. LVS on Mars 2020 represents the first ever use of a reference map during spacecraft EDL. This breakthrough will have profound implications for future lander missions and the scope of scientific inquiry they are able to address. In this paper, we will describe the necessary precursor steps to building the Jezero Crater LVS map, including the methodology to dejitter Context Imager (CTX) images, improve the CTX sensor model, as well as the process used to validate the LVS map accuracy. Key Points: The Lander Vision System used for precision landing by the Mars 2020 mission required unprecedented fidelity in the onboard reference mapThis study describes methods used to generate an onboard reference map with the required fidelityThis study describes methods used to validate the onboard reference map [ABSTRACT FROM AUTHOR]

This paper presents our efforts to characterize the candidate landing region (109°–133°E, 23°–30°N) for Tianwen‐1, China's first mission to Mars, in terms of engineering safety and scientific significance. Topographic analysis reveals that the region has a low elevation around −4,230 m, and 98% of the region have slopes smaller than 8°. The geomorphological mapping and analysis show that the region has an average crater density of about 28 craters (≥200 m in diameter) per 100 square kilometers, with several clusters of high crater densities distributed around the center of the region. There are also pitted cones distributed mainly in the southern part of the region, with a density of approximately 6.6 cones per 100 square kilometers in specific local areas. The region has rock abundances ranging from 1% to 23%, with local clusters of low and high rock abundances. The region comprises four main geological units, including a lowland unit formed in the Late Hesperian and a volcanic unit formed in the Amazonian and Hesperian period. Their specific surface ages are estimated through the analysis of crater size‐frequency distribution. Combining the engineering constraints on surface slopes, crater density, cone density, and rock abundance, a hazard map of the candidate landing region is generated for landing site evaluation and safety assessment. Based on the results, we further discuss the potential scientific outcomes from the exploration in this region. The findings will be helpful for the mission planning and maximization of the scientific return from Tianwen‐1, and complement existing Martian scientific research. Key Points: Topographic, geomorphological, and geologic characterization of the candidate landing region of Tianwen‐1A hazard map of the region combining engineering constraints on slopes, crater density, cone density, and rock abundanceTwo local areas in the region are highlighted as potential landing sites for their low hazard and scientific significance [ABSTRACT FROM AUTHOR]

In this paper we use the Mars implementation of the Planet Weather Research and Forecasting model, MarsWRF, to simulate the Entry, Descent and Landing (EDL) vertical profiles from six past missions: Pathfinder, Mars Exploration Rovers Opportunity and Spirit, Phoenix, Mars Science Laboratory Curiosity rover, and ExoMars 2016 (Schiaparelli), and compare the results with observed data. In order to investigate the sensitivity of the model predictions to the atmospheric dust distribution, MarsWRF is run with two prescribed dust scenarios. It is concluded that the MarsWRF EDL predictions can be used for guidance into the design and planning stage of future missions to the planet, as it generally captures the observed EDL profiles, although it has a tendency to underestimate the temperature and overestimate the density for heights above 15 km. This could be attributed to an incorrect representation of the observed dust loading. We have used the model to predict the EDL conditions that may be encountered by two future missions: ExoMars 2020 and Mars 2020. When run for Oxia Planum and Jezero Crater for the expected landing time, MarsWRF predicts a large sensitivity to the dust loading in particular for the horizontal wind speed above 10‐15 km with maximum differences of up to ±30 m/s for the former and ±15 m/s for the latter site. For both sites, the best time for EDL, that is, when the wind speed is generally the weakest with smaller shifts in direction, is predicted to be in the late morning and early afternoon. Plain Language Summary: One of the most critical stages of a mission to another planet is the Entry, Descent and Landing (EDL) stage. If not successful, the entire mission will be deemed a failure. The thin atmosphere, unpredictable winds, variable dust content, and rough terrain make an EDL on Mars particularly challenging. In this paper, a simplified Martian mesoscale model is used to simulate the EDL conditions encountered by six past missions to the planet with the model predictions evaluated against the observed measurements. By and large, the model successfully captures the observed density, temperature, pressure, and horizontal wind vertical profiles in the lowest 30 km, where the most critical phase of the EDL takes place. The main discrepancy with respect to the observed profiles is for heights above 15 km and is probably due to an incorrect representation of the vertical profile of atmospheric dust, which strongly affects heating rates and hence other variables. The model is subsequently run for the proposed landing sites of ExoMars 2020 (Oxia Planum) and Mars 2020 (Jezero Crater) missions and for the expected time of EDL. For both sites, the model predictions indicate a strong sensitivity to the dust loading, with the most favorable time for the EDL, that is, when the horizontal wind speed is generally the weakest with smaller shifts in wind direction, being the late morning and early afternoon. Key Points: MarsWRF reproduces well the observed EDL vertical profiles from six past missions to the planetMarsWRF EDL predictions can be used for guidance into the design and planning stage of future missions to the planetFor ExoMars 2020 and Mars rover 2020 missions, the best time for EDL seems to be in the late morning and early afternoon [ABSTRACT FROM AUTHOR]

China's first Mars sampling return mission (Tianwen‐3) is designed to launch and retrieve samples around 2030. Three tentative landing areas (TLAs) (Amazonis, Chryse and Utopia Planitiae, i.e., TLA‐A, TLA‐C and TLA‐U) are selected based on elevation <−2,000 m and latitude between 17° and 30°N. As a dominant feature of Martian meteorology, dust storms manifest in all seasons and affect the accuracy and safety of Mars exploration missions. Tianwen‐3's landing, sampling and ascent phases are in the dust storm season. Therefore, analyzing dust storm activity around landing areas is significant for the Tianwen‐3 mission. According to Mars Daily Global Maps taken by Mars Orbiter Camera spanning Martian years 24–28, 2,476 dust storm events around the three TLAs were identified in this research. Dust storm temporal probabilities within TLA‐A, TLA‐C and TLA‐U were calculated as 0%–44.69%, 0%–66.29% and 0%–33.64%, separately. Dust storm spatial probabilities around the TLA‐A, TLA‐C and TLA‐U were computed, with ranges of 0%–10.71%, 0%–14.55% and 0%–19.96% during the T1 period (Ls = 161–309°), and 0%–6.75%, 0%–7.65% and 0%–8.26% during the T2 period (Ls = 342‐55°), respectively. Finally, considering the temporal and spatial distribution of dust storms, we recommend the T2 period as the launch scenario. Three safe periods (Ls = 2–18°, 4–12°, and 356–4°) were assigned for the entry‐descent‐landing (EDL) phase, along with one period (Ls = 45–55°) for the take‐off and ascent phase. Five circular landing zones with dust storm spatial probability <3% were selected for the Tianwen‐3 mission. Plain Language Summary: Tianwen‐3 is the first Mars sampling return mission by China, scheduled to launch and return samples around 2030. Three tentative landing areas (TLAs), Amazonis Planitia (TLA‐A), Chryse Planitia (TLA‐C), and Utopia Planitia (TLA‐U), located at elevations of <−2,000 m and within the latitude range of 17°–30°N. Three TLAs are situated along the trajectories of Martian dust storm sequences. The harsh dusty conditions significantly impact the success of the Mars exploration mission. Therefore, it is meaningful to analyze the dust storm occurrence probability within and around three TLAs. In this study, we utilized Mars Global Surveyor (MGS) Mars Daily Global Maps to (a) detect the dust storm events around three TLAs in five consecutive Mars years (MY 24–28); (b) calculate and analyze the temporal and spatial probabilities of dust storm occurrence; and (c) designate the safe landing areas, the preferred take‐off and ascent and entry‐descent‐landing (EDL) periods for the Tianwen‐3 mission. Key Points: Dust storms within three tentative landing areas exhibit distinct seasonality and heterogeneity throughout a Mars year, with clear solstitial pause periodsDust storm spatial‐temporal analysis reveals that the T2 period is more suitable as the launch scenario for the Tianwen‐3The preferred entry‐descent‐landing period, preferred take‐off and ascent period, and safe landing areas are chosen for the Tianwen‐3 [ABSTRACT FROM AUTHOR]

The image data of the Context Camera (CTX) of the Mars Reconnaissance Orbiter require a flat‐field correction that is currently available as a plain text file in the Planetary Data System "Calib" folders for all CTX Enhanced Data Record releases or automatically implemented as part of the ctxcal application of the Integrated Software for Images and Spectrometers (ISIS). We noticed (a) differences between these two flat‐fields and (b) residual edge darkening (vignetting) after applying ctxcal. This work examines in detail the edge‐darkening effect over time and creates a new improved flat‐field calibration file to be implemented into the ISIS ctxcal application as a new default. We introduce a method to quantify the vignetting effect and its residuals after regular ISIS calibration. With the old calibration, the amount of residual edge‐darkening is about eight percent. We prove that the new calibration does remove the effect completely, does not introduce any artifacts and qualitatively and quantitatively validate newly calibrated images. Mosaics produced with images that have been calibrated with our new flatfield show immediately less striping issues, without the application of any standard mosaicking‐related tone‐matching techniques. Plain Language Summary: The image data of the Context Camera (CTX) of the Mars Reconnaissance Orbiter require a correction of optical (vignetting) and electronic (pixel‐to‐pixel variations) effects that need to be applied for each image before scientific work can commence. These corrections are commonly called flat‐field corrections. In this work we notice that the existing correction for CTX leaves an edge darkening in the images. We review the existing flat‐field correction, examine how it might change over time and create a new version of this correction that shall be implemented as a new default into the widely used image processing framework ISIS, so that other scientists can easily benefit from our improvements. Key Points: We provide an improved in‐flight flat‐field calibration for the Context Camera using the Integrated Software for Imagers and SpectrometersResidual edge darkening effects are now removed with this new calibrationThe calibration proves to be stable during the overall mission time so far [ABSTRACT FROM AUTHOR]

The Mars Global Digital Dune Database (MGD3) contains information on Martian dune fields and prepared manually from the Thermal Emission Imaging System (THEMIS; 100 m/pixel) images. Although the MGD3 outlines dune fields, it overlooks the recognition of smaller dune forms. This paper aims to identify individual dunes from a semiautomated object‐based image analysis technique and characterize dune materials at Hargraves crater, Mars. MGD3 would benefit to be updated for an improved understanding of the Martian surface and its atmospheric mechanisms at a local scale. An object‐based image analysis technique was applied here to the Context Camera (CTX; 6 m/pixel) data set to extract dune data in a more efficient, reliable, and accurate fashion. This study is a test case in validating a remote sensing method that has wide applicability to the entire Martian surface resulting in an update to the dune database at a higher spatial resolution—providing a better understanding of surface and atmospheric behavior of Mars at the local scale. We also explored the wind flow and dune stability—presenting an insight into the dune modification mechanism—within the crater. The prevailing wind inside the crater flows to the west‐northwest. The dunes are labeled as active (stability index of 2) and do not appear to have been influenced by subsurface water ice or volatiles. We emphasize that the technique used here has a wide prospect in temporal monitoring of dune sediment flux, dune migration or erosion rates, improving near‐surface airflow modeling, and dune stability analysis. Plain Language Summary: The Mars Global Digital Dune Database (MGD3) contains morphologic information on Martian dune fields. MGD3 has various science applications including atmospheric circulation modeling, planetary climate change, mechanical weathering processes, and future rover lander missions to Mars. However, the database was prepared manually through visual photointerpretation from low‐resolution satellite images of 100 m/pixel and, consequently, overlooked the recognition of smaller dune forms. Thus, MGD3 would benefit to be updated for an improved understanding of the Martian surface and its atmospheric mechanisms including near‐surface wind patterns at a local scale as opposed to the global scale. We used a semiautomated object‐based image analysis (OBIA) technique from higher‐resolution images of ~6 m/pixel—more than 10 times higher spatial resolution compared to the previous imagery. Using the technique, we extracted individual dunes at Hargraves crater in a more efficient, reliable, and accurate fashion. The validated and accurate result in this study indicates the applicability of the OBIA method for the entire surface of Mars. Thus, the application OBIA method will be a great improvement for futures studies on Martian (and terrestrial) dune fields including temporal monitoring with better estimates of sediment flux, dune migration or erosion rates, and improving near‐surface airflow modeling. Key Points: Individual barchan and barchanoidal dunes were extracted from a semiautomated object‐based image analysis techniqueThe dunes are labeled as active with a stability index of 2 and have not been influenced by subsurface water ice or volatileThe validated and accurate result in this study indicates the applicability of the OBIA method for the entire surface of Mars [ABSTRACT FROM AUTHOR]

China's first Mars exploration mission (Tianwen‐1), launched on July 23, 2020 with the goal of "orbiting, landing, and roving," and its tentative landing areas (TLAs) are Chryse Planitia (TLA 1) and Isidis‐Elysium Planitia (TLA 2). Dust storm is a typical activity on Mars; it has strong interaction with atmospheric circulation and will influence the visibility of the Martian surface. To ensure the safety and accuracy for landing, it is meaningful to analyze the probability of dust storm activity during Entry‐Descent‐Landing (EDL) season in TLAs. First, based on Mars Orbiter Camera (MOC) and Mars Color Imager (MARCI) Daily Global Maps (MDGMs) from Mars Years 24–31, we identified 882 dust storms within the 2,000 km radius monitor circle of TLA 2 (short for TLA 2‐C). Second, the average daily probability of dust storm activity (Adp_ds) in TLA 2‐C was calculated, with a range of 0% to 14.13% showing obvious seasonality and discontinuity. Third, we divided TLA 2‐C into 0.5° longitude × 0.5° latitude square grids and calculated their spatial probability of dust storm activity. The spatial probability of dust storm in TLA 2‐C ranged from 0% to 11.87% and generally reduced from north to south. Finally, according to the temporal and spatial dust storm probability in TLA 2 during EDL season, we suggested the optimal landing time of China's Tianwen‐1 mission was in Ls = 20–41° and selected five preferred landing areas with the spatial probability of dust storm <3% for this mission. Plain Language Summary: The first China's Mars exploration mission (Tianwen‐1), will achieve the targets of "orbiting, landing, and roving." There are two tentative landing areas (TLAs) in the latitude range of 5–30°, Chryse Planitia (TLA 1) and Isidis‐Elysium Planitia (TLA 2). TLA 2 is on the south of Utopia which is an important origination area of dust storm sequences in the northern hemisphere. The probability of dust storm activity is an important criterion of atmospheric risk assessment for a Martian surface mission. Thus, it is crucial to evaluate the probabilities and characteristics of dust storm activity in and around TLA 2. In this paper, we used Mars Daily Global Maps (MDGMs) of Mars Orbiter Camera (MOC) and Mars Color Imager (MARCI) to (1) identify and catalog the dust storms in and around TLA 2; (2) calculate and analyze the temporal and spatial probability of dust storms in and around TLA 2; and (3) select the preferred landing time and areas for Tianwen‐1 mission based on the temporal and spatial probability of dust storm activity in TLA 2. Key Points: The temporal probability of dust storm activity in Isidis‐Elysium Planitia shows obvious seasonal and inconsecutive activityThe spatial probability of dust storm activity in Isidis‐Elysium Planitia is generally reduced from north to southThe optimal landing time was in Ls = 20–41°, and five preferred landing areas were selected for Tianwen‐1 [ABSTRACT FROM AUTHOR]

The high‐resolution stereo camera mounted on the Mars Express (MEX) spacecraft of the European Space Agency is specifically designed for planetary photogrammetry and mapping missions. High‐precision geometric calibration is required to maintain the geometric quality of satellite imaging. This study aimed to develop a Martian geometric calibration model based on the detector look angle and offset matrix to compensate for systematic errors caused by the camera system parameters, Doppler shift measurements, and other parameters of the interior and exterior orientation during positioning. Moreover, the difficulty in identifying high‐precision geometric ground control points from extra‐terrestrial imagery was addressed by proposing an iterative Mars Orbiter Laser Altimeter extraction algorithm based on the similarity measure of terrain relief. Using this algorithm, constraint conditions were established, and a calibration model was introduced to achieve in‐orbit geometric calibration of the MEX satellite. The proposed method is effective in reducing the distortion of the camera in calibration images from 12 pixels to <1 pixel, both before and after calibration. Moreover, the plane accuracy of validation images improved from approximately 900 to 200 m, while elevation accuracy improved from 500 to 100 m, verifying the effectiveness of the proposed method. Key Points: A geometric calibration model based on detector look angle and an offset matrix was developed for planetary photogrammetryThe proposed method is effective in reducing camera misalignment in calibration images from 12 pixels to <1 pixelAccuracy of validation images improved from 900 to 200 m, and elevation accuracy improved from 500 to 100 m [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]

The evolution of the climate and hydrochemistry of Mars is still a mystery but it must have been at least occasionally warm and wet to have formed the ancient fluvial and lacustrine landforms observed today. Terrestrial examples and geochemical modeling under proposed early Mars conditions show that zeolite minerals are likely to have formed under alkaline (pH > 8) conditions with low water/rock ratio and surface temperatures below 150°C. The identification and spatial association of zeolites on the surface of Mars could thus be used to reconstruct the paleoclimate, paleohydrochemistry, and geological evolution of some locations on Mars. Previous studies identified the zeolite analcime and discuss the difficulties of identifying other zeolite species on the surface of Mars using orbital spectroscopy. We used published global mineralogical, geological, geomorphological, hydrological, physical, and elemental abundance maps and the locations of hydrous minerals detected and mapped using orbital data to create a map that delineates favorable areas to look for zeolites on Mars. We used the data‐driven fuzzy‐based Weights‐of‐Evidence method to identify and map favorable areas for zeolites on the surface of Mars up to ±40° latitude toward the poles. The final map shows that the eastern and western Arabia deposits, some sites in the Medusae Fossae formation, and some areas within and near Valles Marineris, Mawrth Vallis, highlands north of Hellas, and the Terra Cimmeria and Terra Sirenum regions would be favorable areas to look for zeolites using targeted orbital spectral analysis or future in situ observations. Plain Language Summary: Our knowledge of early Mars environmental conditions is limited. Field examples from the Earth and computer models that simulate how zeolites form under early martian conditions showed that they prefer water‐limited, high pH conditions and surface temperatures below 150°C. Therefore, if zeolite minerals are present in certain locations on the surface of Mars, based on their presence, we can infer the geological and environmental history of that location. We used a computer model to identify where zeolite minerals can be present on Mars, based on existing maps and data sets of martian surface features, properties, and compositions. Using that model, we identified several areas of Mars that would have been favorable for zeolites, which could be targeted for future more detailed studies. Key Points: This study creates a map to delineate the favorable areas to look for zeolites on the surface of MarsWe used the data‐driven fuzzy‐based Weights‐of‐Evidence method to identify and map favorable areas for zeolites using published global maps on MarsThe final map shows the prospective areas for zeolites which could be used for more detailed orbital data analysis or future in situ observations [ABSTRACT FROM AUTHOR]

The NASA Ames Mars Global Climate Model (MGCM) software has been in steady use at NASA for decades and was recently released to the public. This model simulates the complex interactions of various weather cycles that exist on Mars, namely the Dust Cycle, the CO2 Cycle, and the Water cycle. Utilized by NASA, the MGCM is used to help understand their empirically observed data through the use of sensitivity studies. However, these sensitivity studies are computationally taxing, requiring weeks to run. To address this issue, we have trained a surrogate model using Gaussian processes (GP) that can emulate the output of this model with relatively small amounts of data in a reduced amount of time (on the order of minutes). We demonstrate the effectiveness of our emulator using backward error. Plain Language Summary: The NASA Ames Mars Global Climate Model (MGCM) is a computer model that simulates the weather on Mars. The MGCM is used by NASA to help understand weather data collected from satellites and other sources. The model has many inputs, the correct values of which are unknown, so it is often run many times with varying input values. Each run of the MGCM takes a long time, so running enough times to gather all of the desired outputs can take weeks. To address this issue, we have developed a method to approximate the output of the MGCM through the use of a machine learning model. This model requires a relatively small amount of data to train and once trained can approximate the MGCM output accurately and very quickly. Key Points: Gaussian Process emulation is effective at vastly decreasing the required runtime for sensitivity studies using the Mars Global Climate Model (MGCM)The use of Gaussian Process emulation is remarkably accurate for the MGCMGaussian Process emulation has significant potential to support more refined studies that would otherwise be computationally unfeasible [ABSTRACT FROM AUTHOR]

The Mars 2020 Mastcam‐Z stereo camera investigation enables the generation of three dimension (3D) data products needed to visualize and analyze rocks, outcrops, and other geological and aeolian features. The Planetary Robotics Vision Processing framework "PRoViP" as well as the Instrument Data System on a tactical—sol‐by‐sol—timeframe generate 3D vision products, such as panoramas, distance maps, and textured meshes. Structure‐from‐motion used by the Advanced Science Targeting Toolkit for Robotic Operations (ASTTRO) "Landform" tool and long baseline stereo pipelines add to the 3D vision products' suite on various scales. Data fusion with textured meshes from satellite imagery and 3D data analysis and interpretation of the resulting large 3D data sets is realized by visualization assets like the Planetary Robotics Vision 3D Viewer PRo3D, the 3D Geographical Information System GIS CAMP (Campaign Analysis Mapping and Planning tool), the ASTTRO 3D data presentation and targeting tool, and the Mastcam‐Z planning tool Viewpoint. The pipelines' workflows and the user‐oriented features of the visualization assets, shared across the Mars 2020 mission, are reported. The individual role and interplay, complements and synergies of the individual frameworks are explained. Emphasis is laid on publicly available 3D vision data products and tools. A representative set of scientific use cases from planetary geology, aeolian activity, soil analysis and impact science illustrates the scientific workflow, and public data deployment modes are briefly outlined, demonstrating that 3D vision processing and visualization is an essential mission‐wide asset to solve important planetary science questions such as prevailing wind direction, soil composition, or geologic origin. Plain Language Summary: Image processing enables to describe the surface of Mars in three dimension (3D) using the Mastcam‐Z stereo cameras' images. The 3D reconstruction of the rocks, geological outcrops, as well as aeolian and mineralogical features, are crucial for understanding the planet's past. Image processing tools to reconstruct the surface of Mars from the images are available to the Mars 2020 Team, generating 3D data products with various information about the surface on Mars like elevation maps or distance maps that record the 3D coordinates of each point. To interpret these products, tools needed for their visualization and analysis are presented here. In a combination with data from other sensors or sources—including 3D models obtained from satellite, and at different scales the interpretation of the processed products is enhanced. The reader learns about the synergies and interplay between these tools, including publicly available tools. Demonstrative planetary science examples, processed by the Mastcam‐Z science team with the above mentioned tools, are presented. Geological features, such as wind activity, soil analysis, and impact science, are analyzed, illustrating the scientific work carried out and in particular the benefit of 3D vision processing and visualization for such analysis work. Key Points: The Mars 2020 Mastcam‐Z investigation's stereoscopic zoom camera pair enables the assembly of 3D models of the rover environmentProcessing and visualization for scientific 3D data exploitation establishes mission science in full knowledge about spatial relationshipsImportant scientific use cases for Mastcam‐Z 3D vision processing and visualization illustrate the importance of 3D for Mars science [ABSTRACT FROM AUTHOR]

NASA's Mars 2020 and ESA's ExoMars will collect Raman measurements in dusty field conditions obscuring underlying rocks. This presents a challenge for remote Raman measurements at distances where mechanical or ablative sample cleaning is not straightforward. Historically, probing broad lithostratigraphic suites has been thwarted by the need for pristine targets and high‐quality spectra. We provide a means of identifying Raman spectra of common rock‐forming silicate, carbonate, and sulfate minerals under low signal‐to‐noise‐ratios, Mars‐like conditions using a convolutional neural network (CNN). The CNN was trained on the Machine Learning Raman Open Data set data set with 500,000+ Raman spectra of hand samples/powder mixtures (5,000+ spectra/mineral class). Diversity in sample microtopography, orientation, and crystallinity simulated varying laser focuses and spectral quality, and no traditional spectral preprocessing such as cosmic ray or baseline removal was employed. The CNN identified low‐intensity Raman scatterers (micas and amphiboles), mixed minerals, and distinguished between mineral endmembers with +99% success. We present among the first known implementations of "big data" machine learning using varied, high‐volume Raman spectral datasets. The pattern recognition abilities of CNNs can facilitate scientist Raman spectral interpretation on Earth and autonomous rover decision‐making on planets like Mars; increasing scientific yield, correcting human classification errors, reducing the need for thorough target dust removal during evaluative measurements, and streamlining the data communications pipeline—saving time and resources. This study examines an end‐to‐end development process for creating a deep learning algorithm sensitive to varieties of Raman spectra and provides guidelines for CNN model development at the interface of Raman spectroscopy, deep learning, and planetary science. Plain Language Summary: We collected thousands of spectra from rocks and minerals that are found on Earth and Mars and trained a computer to automatically identify them using an algorithm called a convolutional neural network or CNN. This is an effective but difficult algorithm to fine tune for Raman spectra as it requires a lot of training. A CNN works like an artificial brain with firing neurons. This brain can be uploaded onto Mars rovers such as NASA's Curiosity and Perseverance so that they can automatically identify rocks and minerals on Mars without human guidance. Doing this will accelerate scientific discovery while saving crucial mission time and energy. We essentially programmed the "brains" of a rock and mineral identification "tricorder". Key Points: Identified minerals and mineral mixtures under dusty, low signal, Mars‐like conditions using Raman spectroscopy and machine learningImplemented a convolutional neural net on Machine Learning Raman Open Data set‐a dedicated Raman machine learning data set operating in a statistically significant domainGeneral guidance given for convolutional neural network model development deployed on custom Raman spectra test sets for automated mineral identification [ABSTRACT FROM AUTHOR]

Rocks on the Martian surface exhibit signatures of geological activities. Rock distribution is also an important factor for landing site selection for exploration missions. This study investigated the rock abundance and erosion rate at the landing site of the Chinese Mars rover, Zhurong, in southern Utopia Planitia. A convolutional neural network based method was developed for rock detection from the images (0.7 m/pixel) obtained by using the high‐resolution imaging camera (HiRIC) onboard the Tianwen‐1 orbiter. Approximately 10,000 rocks with a minimum diameter of 1.4 m (2 pixels on the image) were extracted from the HiRIC images covering the Zhurong landing site and its neighboring region. According to the results, the rock abundance at the Zhurong landing site was approximately 5%. Measurements from the ground images acquired by the Zhurong rover after landing confirmed a rock abundance of approximately 5% at the landing site, consistent with the orbital measurement before landing. Furthermore, we investigated the rock erosion rate at the Zhurong landing region. Rock abundance was negatively correlated with the crater retention age and positively correlated with crater diameter. The obtained rock breakdown rate (0.054 nm/y to 0.074 nm/y) and surface denudation rate by filled volume of craters (0.104 nm/y to 0.209 nm/y) were in agreement with the values previously reported for the Amazonian period on Mars. The low erosion rate implies a dry climate and the absence of fluvial erosion processes in the Amazonian period. Key Points: Rock abundance of ∼5% identified at Zhurong landing site from orbital and ground measurementsRock breakdown and surface denudation rate at Zhurong landing site and its neighboring region are estimatedLow erosion rates suggest an arid climate in the Amazonian period [ABSTRACT FROM AUTHOR]

Rock shapes and heights around the InSight lander are examined to refine the degradation history of the 27 m‐diameter Homestead hollow. Results document decreasing average exposed rock height and increasing percentage of rocks where height comprises the short axis from outside to within the hollow and support prior models of ejecta deflation accompanied by hollow infilling. We estimate 0.3 m of deflation at the current rim that is realistic compared to rock relief, original ejecta thickness, and predicted aeolian contributions to infilling. We also find that shapes of embayed basalt rocks outside the hollow appear platy, bladed, and elongate in a triangular form factor plot, and more discoidal and bladed in an axes ratio plot. By contrast, expected shapes based on terrestrial studies of basalt rocks are mostly compact, compact platy, compact bladed, compact elongated, platy, bladed, and elongate in triangular form factor plots, and equant with lesser, but significant disc‐ and blade‐shaped rocks in axes ratio plots. We find addition of 10 cm to the heights of rocks near the hollow rim, to account for continued partial embedding in ejecta, yields the best match between observed and expected rock shapes. Exposure of small ejecta rocks in the hollow supports degradation rates of 10−4 m/Myr during most of hollow history. Results indicate that deflation from ejecta accompanied by downwind deposition in the hollow can account for the current degraded form of the crater. Our approach is a new tool for characterizing small crater degradation on regolith‐covered lava plains on Mars. Key Points: Rock heights and shapes at Homestead hollow indicate early transport of deflated ejecta sediments can account for infilling of the craterNear‐rim rock heights and shapes relative to the expected original versus remnant ejecta thickness indicates 30 cm deflation at the current rimExposure of later arriving, small ejecta rocks in the hollow supports very low estimates of degradation over most hollow history [ABSTRACT FROM AUTHOR]

The Chemistry and Camera (ChemCam) instrument on board the Mars Science Laboratory (MSL) rover Curiosity has collected a very large and unique data set of in‐situ spectra and images of Mars since landing in August 2012. More than 800,000 single shot laser‐induced breakdown spectroscopy (LIBS) spectra measured on more than 2,500 individual targets were returned so far by ChemCam. Such a data set is ideally suited for the application of statistical methods for the recognition of patterns that are difficult to observe by humans. In this work, we develop an approach relying on the feature extraction method Non‐Negative Matrix Factorization (NMF) and the repetition of k‐means clustering to classify ChemCam spectra. A strong consistency of the clustering results among the repetitions were found, which allowed us to identify six clusters representing the dominant compositions measured by ChemCam in Gale crater so far. By tracking clusters across the rover traverse from landing to sol 2756, we are able to provide a chemostratigraphic overview of the Gale crater from the ChemCam perspective. Transitions between major geologic groups (such as the Bradbury and the Mt. Sharp groups) are identifiable demonstrating that they are compositionally distinct, consistent with previous work. Compositional differences between their members also appear in the results. Furthermore, a first approach in which a random forest classifier was trained and validated with the obtained cluster assignments, reveals promising results for predicting cluster memberships of new ChemCam LIBS data acquired after sol 2756. Key Points: With a combination of feature extraction and repeated k‐means clustering applied to ChemCam LIBS data, we identify six clusters representing dominant compositions in Gale craterThe cluster detections are in agreement with the chemostratigraphy explored by CuriosityWe successfully trained a random forest classifier with the obtained cluster labels and used it to classify recent ChemCam targets [ABSTRACT FROM AUTHOR]

To unequivocally discover the actual presence of life or even of near surface liquid water on extraterrestrial planetary bodies would be a key scientific breakthrough for humankind. For this reason, studying similar environments on Earth is essential to understanding the processes shaping such extraterrestrial objects. The Yungay area in the Chilean part of the Atacama Desert is deemed to be particularly suitable as a terrestrial analog of Mars (TAM). In this study, we deployed multi‐frequency ground penetrating radar (GPR) and a six‐coil electromagnetic induction (EMI) system with a maximum depth of investigation of 1.8 m over an area of 0.66 hectares (110 x 60 m). By applying a LOWESS algorithm to the GPR envelope data, we aimed to extrapolate the strongest amplitudes indicating physical contrasts to 3D. The results were constrained with two existing pits 100 m apart. Whereas clay content was mostly responsible for GPR signal attenuation, changes in texture and stratigraphy were linked with strong amplitude reflections. EMI showed very low apparent electrical conductivity (ECa) values between 0 and 5 mS/m. The ECa variability could be linked to changes in clay content with depth. This agreed with the surface obtained from the LOWESS algorithm. Although soil samples are still necessary to constrain the measured signals, we showed the benefits of applying geophysics for large‐scale characterization and can conclude that these two methods are suitable for such hyperarid TAM environments. A similar routine if applied on the surface of Mars could deliver promising results for similar characteristics. Plain Language Summary: Recently, NASA sent the Perseverance rover to Mars (see https://mars.nasa.gov/mars2020/spacecraft/instruments/), which is equipped with subsurface radar and other tools to measure surface and subsurface features. The Zhurong Mars rover was also launched by the Chinese government as part of its Tianwen‐1 mission (see https://www.planetary.org/space-missions/tianwen-1). Such missions apply geophysical methods to noninvasively and indirectly measure the physical properties of the subsurface on a large scale. However, real soil core or profile information is needed to validate the measured signals. In this study, we used ground‐penetrating radar and electromagnetic induction to investigate the hyperarid site of Yungay, Atacama, Chile, which is reported to be similar to certain regions of Mars. Our goal was to provide a case study that can be used to calibrate and validate the geophysical data measured on Mars in the near future. We were able to correlate the geophysical data with two excavated pits 100 m away from each other and to upscale this information to an area of 110 x 60 m. As in the case of Yungay, we expect geophysical methods to be primarily influenced by changes in soil particles, compaction, and layering when employed on Mars. Key Points: Noninvasive geophysical characterization of the hyperarid and Mars‐like environment of Yungay, Chile using EMI and GPRCorrelation of ground penetrating radar at the point scale with two open pits located 100 m away from each otherUpscaling point‐scale information using ground penetrating radar and electromagnetic induction to an area of 0.66 hectares (110 x 60 m) [ABSTRACT FROM AUTHOR]

Rocks around the InSight lander were measured in lander orthoimages of the near field (<10 m), in panoramas of the far field (<40 m), and in a high‐resolution orbital image around the lander (1 km2). The cumulative fractional area versus diameter size‐frequency distributions for four areas in the near field fall on exponential model curves used for estimating hazards for landing spacecraft. The rock abundance varies in the near field from 0.6% for the sand and pebble‐rich area to the east within Homestead hollow to ∼3–5% for the progressively rockier areas to the south, north, and west. The rock abundance of the entire near field is just over 3%, which falls between that at the Phoenix (2%) and Spirit (5%) landing sites. Rocks in the far field (<40 m) that could be identified in both the surface panorama and a high‐resolution orbital image fall on the same exponential model curve as the average near‐field rocks. Rocks measured in a high‐resolution orbital image (27.5 cm/pixel) within ∼500 m of the lander that includes several rocky ejecta craters fall on 4–5% exponential model curves, similar to the northern and western near‐field areas. As a result, the rock abundances observed from orbit fall on the same exponential model rock abundance curves as those viewed from the surface. These rock abundance measurements around the lander are consistent with thermal imaging estimates over larger pixel areas as well as expectations from fragmentation theory of an impacted Amazonian/Hesperian lava flow. Key Points: Rocks measured within 10 m, 40 m, and ∼500 m of the InSight lander cover 0.6–5%, ∼3%, and 4–5% cumulative fractional area of the surfaceThe rock size‐frequency distributions observed from the orbit and the surface are on similar exponential model curvesRock abundance at InSight is between the Phoenix and Spirit landing sites and is consistent with orbital thermal imaging estimates [ABSTRACT FROM AUTHOR]

During its first seven years of operation, the Sample Analysis at Mars Tunable Laser Spectrometer (TLS) on board the Curiosity rover has detected seven methane spikes above a low background abundance in Gale crater. The methane spikes are likely sourced by surface emission within or around Gale crater. Here, we use inverse Lagrangian modeling techniques to identify upstream emission regions on the Martian surface for these methane spikes at an unprecedented spatial resolution. Inside Gale crater, the northwestern crater floor casts the strongest influence on the detections. Outside Gale crater, the upstream regions common to all the methane spikes extend toward the north. The contrasting results from two consecutive TLS methane measurements performed on the same sol point to an active emission site to the west or the southwest of the Curiosity rover on the northwestern crater floor. The observed spike magnitude and frequency also favor emission sites on the northwestern crater floor, unless there are fast methane removal mechanisms at work, or either the methane spikes of TLS or the non‐detections of ExoMars Trace Gas Orbiter cannot be trusted. Key Points: Back trajectory analyses are performed for the methane spikes detected by the Mars Science Laboratory at Gale craterUpstream emission regions are mapped out at unprecedented spatial resolutionsIf the lifetime of methane is not overestimated, the methane spikes must be sourced by very nearby emission in northwestern Gale crater [ABSTRACT FROM AUTHOR]

In December 2018, the NASA InSight lander successfully placed a seismometer on the surface of Mars. Alongside, a hammering device was deployed at the landing site that penetrated into the ground to attempt the first measurements of the planetary heat flow of Mars. The hammering of the heat probe generated repeated seismic signals that were registered by the seismometer and can potentially be used to image the shallow subsurface just below the lander. However, the broad frequency content of the seismic signals generated by the hammering extends beyond the Nyquist frequency governed by the seismometer's sampling rate of 100 samples per second. Here, we propose an algorithm to reconstruct the seismic signals beyond the classical sampling limits. We exploit the structure in the data due to thousands of repeated, only gradually varying hammering signals as the heat probe slowly penetrates into the ground. In addition, we make use of the fact that repeated hammering signals are sub‐sampled differently due to the unsynchronized timing between the hammer strikes and the seismometer recordings. This allows us to reconstruct signals beyond the classical Nyquist frequency limit by enforcing a sparsity constraint on the signal in a modified Radon transform domain. In addition, the proposed method reduces uncorrelated noise in the recorded data. Using both synthetic data and actual data recorded on Mars, we show how the proposed algorithm can be used to reconstruct the high‐frequency hammering signal at very high resolution. Key Points: Hammering of the InSight heat probe generates high‐frequency seismic signals that exceed the Nyquist frequency of the seismometerWe developed a new data acquisition and reconstruction workflow that allows for the recovery of the full‐bandwidth hammering signalsDuring hammering, we deliberately turned off the seismometer's anti‐aliasing filters and reconstructed the aliased signal using a sparseness‐promoting algorithm [ABSTRACT FROM AUTHOR]

The tidal response of Mars, due to the Sun and the Martian moons, Phobos and Deimos, provides information about the interior structure of Mars. By using the Very Broad Band (VBB) seismometer of Seismic Experiment for Interior Structure (SEIS) as a gravimeter on the surface of Mars, the InSight mission will provide the long‐period data suited to tidal analysis: most notably, the proximity of Phobos implies that degree 2, 3, 4, and further tides will be detectable by the VBB and are expected to provide information about the rheology at different depths within Mars. In order to expedite the recovery of these tidal signals in the SEIS measurements, we model the tides raised by Phobos using a tidal potential deduced from JPL Horizons ephemerides. From this potential, we calculate the expected tidal acceleration at InSight's location and gravimetric factors using a set of plausible interior models of Mars. To simulate the expected long period signal on the VBB seismometer, we use the InSight Auxiliary Payload Sensor Suite data to model the noise seen at low frequency by SEIS mainly due to temperature and pressure variations. Based on this synthetic signal, by applying filtering methods such as stacking and matched filtering to these synthetic data, we show that by recovering the gravimetric factors, it should be possible to constrain the state of the core and its size with an accuracy of 125 km after two Earth years. Plain Language Summary: On Mars since November 26, 2018, the NASA InSight mission made weather measurements of the atmosphere's temperature, wind, and pressure. It has also put a seismometer at the surface of Mars to see Mars quakes. However, the seismometer can also be used to measure the tides due to the Martian moon Phobos: by deforming the surface of the planet, the Phobos tides will create a change in the gravity at the surface of Mars, which can be recorded. As Phobos is closer to Mars than the Moon is to Earth, the shape of the tides on Mars is more complicated, but can be used to determine the interior structure of Mars. In particular, its deepest part, the core, is not well determined: it is still unsure whether it is liquid or solid, and how big it is. We model the expected tides at InSight's location and noises due to temperature and pressure variations based on the measurements made to guess what the seismometer will record. This study shows that after two Earth years, we should be able to see the Phobos tides accurately enough to know the core state and size with an accuracy of 125 km. Key Points: The Phobos tides of degree 2, 3, and 4 should be detectable by the Very Broad Band seismometer on InSight's Seismic Experiment for Interior Structure (SEIS)We model these tides, the Martian interior and SEIS low frequency noise with recent InSight dataOver 2 Earth years, determining the core state and size with 125 km accuracy should be possible [ABSTRACT FROM AUTHOR]

The entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance Rover will act as a seismic source of known temporal and spatial localization. We evaluate whether the signals produced by this event will be detectable by the InSight lander (3,452 km away), comparing expected signal amplitudes to noise levels at the instrument. Modeling is undertaken to predict the propagation of the acoustic signal (purely in the atmosphere), the seismoacoustic signal (atmosphere‐to‐ground coupled), and the elastodynamic seismic signal (in the ground only). Our results suggest that the acoustic and seismoacoustic signals, produced by the atmospheric shock wave from the EDL, are unlikely to be detectable due to the pattern of winds in the martian atmosphere and the weak air‐to‐ground coupling, respectively. However, the elastodynamic seismic signal produced by the impact of the spacecraft's cruise balance masses on the surface may be detected by InSight. The upper and lower bounds on predicted ground velocity at InSight are 2.0 × 10−14 and 1.3 × 10−10 m s−1. The upper value is above the noise floor at the time of landing 40% of the time on average. The large range of possible values reflects uncertainties in the current understanding of impact‐generated seismic waves and their subsequent propagation and attenuation through Mars. Uncertainty in the detectability also stems from the indeterminate instrument noise level at the time of this future event. A positive detection would be of enormous value in constraining the seismic properties of Mars, and in improving our understanding of impact‐generated seismic waves. Plain Language Summary: When it lands on Mars, NASA's Perseverance Rover will have to slow down rapidly to achieve a safe landing. In doing this, it will produce a sonic boom and eject two large balance masses which will hit the surface at very high speed. The sonic boom and balance mass impacts will produce seismic waves which will travel away from Perseverance's landing site. Here, we evaluate whether these seismic waves will be detectable by instruments on the InSight lander (3,452 km away). We predict that the waves from the balance mass impacts may be detectable. If the waves are recorded by InSight, this would represent the first detection of ground motion generated by a seismic source on Mars at a known time and location. This would be of enormous value in advancing our understanding of the structure and properties of Mars' atmosphere and interior as well as in improving our understanding of how seismic waves are produced by meteorites hitting the surface. Key Points: The entry descent and landing of Mars 2020 (NASA's Perseverance Rover) will act as a seismic source on Mars act as a seismic source on MarsWe evaluate the detectability of the acoustic (atmospheric) and elastodynamic seismic (ground) signalsWe predict the acoustic signal will not likely be detectable by InSight, but the seismic signal may be [ABSTRACT FROM AUTHOR]

The thermal and convective evolution of terrestrial planets like Mars is governed by a number of initial conditions and parameters, which are poorly constrained. We use Mixture Density Networks (MDN) to invert various sets of synthetic present‐day observables and infer five parameters: reference viscosity, activation energy and activation volume of the diffusion creep rheology, an enrichment factor for radiogenic elements in the crust, and initial mantle temperature. The data set comes from 6,130 two‐dimensional simulations of the thermal evolution of Mars' interior. We quantify the possibility of constraining a parameter using the log‐likelihood value from the MDN. Reference viscosity can be constrained to within 32% of its entire range (1019 − 1022 Pa s), when all the observables are available: core‐mantle‐boundary heat flux, surface heat flux, radial contraction, melt produced, and duration of volcanism. Furthermore, crustal enrichment factor (1–50) can be constrained, at best, to within 15%, and the activation energy (105 − 5 × 105 J mol−1) to within 80%. Initial mantle temperature can be constrained to within 39% of its range (1,600–1,800 K). Using the full present‐day temperature profile or parts of it as an observable tightens the constraints further. The activation volume (4 × 10−6 − 10 × 10−6 m3 mol−1) cannot be constrained. We also tested different levels of uncertainty in the observables and found that constraints on different parameters loosen differently, with initial temperature being the most sensitive. Finally, we present how a joint probability model for all parameters can be obtained from the MDN. Plain Language Summary: The mantle of rocky planets like Mars behaves like a highly viscous fluid over geological time scales. Key parameters and initial conditions for the non‐linear partial differential equations governing mantle flow are poorly known. Machine Learning (ML) can help us avoid running several thousand computationally expensive fluid dynamic simulations each time to determine if an observable can constrain a parameter. Using an ML approach, we invert a set of synthetic observables such as present‐day surface heat flux, duration of volcanism and radial contraction to constrain important parameters controlling the long‐term evolution of the planet's interior, such as the reference mantle viscosity or the partitioning of radiogenic heat sources between mantle and crust. We demonstrate that by training a probabilistic ML algorithm on the data and applying it, we can quantify the constraints on parameters. This provides a high‐dimensional framework for analyzing inverse problems in geodynamics. Key Points: Mixture Density Networks provide a probabilistic framework for inverting observables to infer parameters of Mars' interior evolutionReference viscosity, crustal enrichment in heat‐producing elements and initial mantle temperature can be well constrainedActivation energy of diffusion creep can be weakly constrained; constraining activation volume requires new observational signatures [ABSTRACT FROM AUTHOR]

The Central Elysium Planitia (CEP) is one of the youngest geological units on Mars and displays evidence of volcanic and fluvial activities on the surface. The origin of the CEP material has long been debated with a range of hypotheses from purely fluvial to solely volcanic origins. This study presents a comprehensive investigation of SHAllow RADar (SHARAD) data to reveal subsurface radar reflectors over the CEP region. Distribution of the detected radar reflectors show possible connections between the CEP and outflow channels, such as Athabasca Valles and Marte Vallis. Analysis of the radar reflectors in the CEP region show six subsurface layers implying multiple depositional and erosional episodes. One detected subsurface layer is found to correspond to the upper exposed layers of one terraced crater. By measuring the depth accurately of these exposed layers in the derived HiRISE (High Resolution Imaging Scientific Experiment) and CTX (Context Camera) DTMs (Digital Terrain Models) and inverting the dielectric constant combining the layers in radargrams, an interpretation that the filling material contains water ice is favored. Key Points: This work investigates subsurface radar reflectors in the Central Elysium Planitia region based on SHAllow RADar (SHARAD) data and posits an interpretation as to their formationBuried channels in the Cerberus Plain appear to be connected to Marte Vallis, and may also be connected to Athabasca VallesDepths of exposed layers in a terraced crater are measured. The depths appear to correspond to the depth of radar layers, and this retrieval favors an interpretation of shallow buried water ice or composites with other dry low‐density materials [ABSTRACT FROM AUTHOR]