The Perseverance rover has sampled mm-size lithic fragments containing olivine likely from at least two source regions from the surface of an inactive megaripple surface, and fine-grained material from the surface and to a depth of similar to 4-6 cm. Some of the mm-size grains lack a coherent diffraction pattern measured by PIXL, consistent with the presence of poorly ordered secondary phases that have been altered. Analysis of these materials on Earth will allow examination of materials that have experienced aqueous, potentially habitable environments that could contain biosignatures. Fluorescence of three different patterns was detected, consistent with inorganic emissions from silica defects or rare earth elements in certain mineral phases, although organic origin cannot be excluded. Analysis of Autofocus Context Imager and Wide Angle Topographic Sensor for Operations and eNgineering images of the subsurface material and MEDA thermal inertia measurements indicate average grain sizes of similar to 125 and similar to 150 mu m, respectively, for the bulk material within the megaripple. The fine-grained material in the sampling location indicates chemical compositions similar to previously proposed global components as well as airfall dust. In situ and associated atmospheric measurements provide evidence of recent processes likely including water vapor in soil crust formation. The sampled material will therefore help elucidate the formation of Martian soils; current surface-atmosphere interactions; the composition, shape, and size distribution of dust grains valuable for studies of past and present Martian climate and for assessing potential health and other risks to human missions; and ancient, aqueously altered environments that could have been habitable, and, if Mars contained life, possibly contain biosignatures.

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 similar to 17 m and similar to 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.

Mars Reconnaissance Orbiter (MRO), with its arrival in 2006 and nearly continuous operation since, has provided data for the study of martian polar processes spanning nine Mars years. Mars' polar deposits have long been thought to preserve records of past climates, potentially readable like terrestrial ice cores. However, unraveling millions of years of history in the ice depends on understanding Mars' current and recent-past climate, including the interactions of atmospheric and surface processes. MRO has allowed for revolutionary discoveries, long-term monitoring of ongoing processes, and multiple complementary datasets to address the question of how the polar ice deposits reflect climatological changes. In part, MRO has been able to do this from its variety of instrumentation simultaneously observing interannual changes in geomorphology of the surface in up to similar to 25 cm/pixel detail, repeatable processes and changes in the atmosphere, and surface composition, as well as investigating signs of past changes recorded in the icy polar layered deposits. In this paper, we summarize the contribution of MRO to our current understanding of Mars polar science, and in particular how MRO's longduration mission has improved our understanding of the fundamental volatile cycles on Mars.

The Mars Reconnaissance Orbiter has been orbiting Mars since 2006 and has acquired >80,000 HiRISE images with sub-meter resolution, contributing to over 2000 peer-reviewed publications, and has provided the data needed to enable safe surface landings in key locations by several rovers or landers. This paper describes the changes to science planning, data processing, and analysis tools since the initial Primary Science Phase in 2006-2008. These changes affect the data used or requested by the community and how they should interpret the data. There have been a variety of complications to the dataset over the years, such as gaps in monitoring due to spacecraft and instrument issues and special events like the arrival of new landers or rovers on Mars or global dust storms. The HiRISE optics have performed well except for a period when temperature uniformity was perturbed, reducing the resolution of some images. The focal plane system now has 12 rather than 14 operational detectors. The first failure (2011) was a unit at the edge of the swath width, reducing image width by 10% rather than creating a gap. The recent (2023) failure was in the middle of the swath. An unusual problem with the analog-to-digital conversion of the signal (resulting in erroneous data) has worsened over time; mitigation steps so far have preserved full-resolution imaging over all functional detectors. Soon, full-resolution imaging will be narrowed to a subset of the detectors and there will be more 2 x 2 binned data. We describe lessons received for future very high-resolution orbital imaging. We continue to invite all interested people to suggest HiRISE targets on Mars via HiWish, and to explore the easy-to-use publicly available images.

Reliable detection and characterization of water ice on the Martian surface is pivotal to not only understand its present and past climate, but to also provide valuable information on in-situ resource availability and distribution for future human exploration missions. Ice-rich features are currently identified with visible/near-IR (VNIR), thermal IR and radar data. However, their coarse spatial scale sometimes limits confident characterization of small (i.e., meter-scale) icy exposures resulting from recent activity like new impacts. Water ice bearing materials possess weaker spectral characteristics at wavelengths shorter than -1030 nm that may be resolved by VNIR imaging instruments like the High Resolution Imaging Science Experiment (HiRISE) and the Colour and Stereo Surface Imaging System (CaSSIS). Our study assesses the spectral capability of HiRISE colour observations to help distinguish high purity water ice exposures from ice-poor materials. We report detailed methodologies for reliable colour characterization of icy surface using unfiltered HiRISE images. We present the first quantitative approach to uniquely characterize high-purity ice-rich materials through spectral shape and spectral parameterization methods at high spatial resolution (-50 cm/pixel). We also present three spectral parameters to aid detection of pure water ice features, while also providing statistical constraints to enable a quantitative interpretation scheme. Our methods are observed to work well in characterizing and separating ice-rich features uniquely from ice-poor and ferrous materials. However, we do observe that these methods have a lower grain size detection limit of -250-300 mu m, and may not be able to uniquely separate frosts from ground ice exposures. We also apply these methods to better constrain the composition of bright materials exposed by recent impacts identified in previous surveys, where substantial evidence for ice-bearing materials was previously unavailable. Overall, our work proposes HiRISE colour-based methods as a novel approach for high-resolution multispectral characterization of ice-rich features on the Martian surface, which is of particular value since the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has ceased operations.

The Murray formation represents fine-grained sedimentary deposition in lacustrine environments within Gale crater, Mars. Both the overall thickness of the Murray formation and its broad uniformity in sedimentary character suggest the potential for a long-lived, groundwater-supported lake system. Rock textures were imaged by the Mars Hand Lens Imager camera at the Pahrump Hills location, which represents the lowermost Murray formation. We analyze data from Pahrump Hills to refine earlier estimates of grain size and grain size distribution, as well as to make detailed observations of diagenetic features and modification of primary sedimentological features. These observations and resulting interpretations provide a detailed look at the dynamic behavior of lake systems on Mars. The lower portions of this exposure are characterized by planar laminated, fine-grained material; the predominant grain size in this region is smaller than that of very fine sand. Diagenetic mineral precipitation is also prominent in these lower layers, evidenced by likely in situ precipitation of lenticular crystals, preferential cementation of laminae in several layers, precipitation of late-diagenetic crystal clusters, and secondary modification of previously deposited crystals. The upper portions of this locality are coarser-grained, varicolored, and contain cross-stratified features. The variation of these features over a relatively thin stratigraphic interval indicates rapid fluctuation in the hydrodynamic behavior of Gale crater lake, similar to that observed in the shallow-water regions of terrestrial closed basin lakes.

Wind‐abraded rocks and aeolian bedforms have been observed at the Mars 2020 Perseverance landing site, providing evidence for recent and older wind directions. This study reports orientations of aeolian features measured in Perseverance images to infer formative wind directions. It compares these measurements with orbital observations, climate model predictions, and wind data acquired by the Mars Environmental Dynamics Analyzer. Three‐dimensional orientations of flute textures on rocks, regolith wind tails extending from behind obstacles, and other aeolian features were measured using Digital Terrain Models derived from Mastcam‐Z and navigation camera (Navcam) stereo images. Orientations of rock flutes measured in images acquired through Sol (Martian day) 400 yielded a mean azimuth of 94° ± 7° (wind from the west). However, similar measurements of regolith wind tails indicate that recent sand‐driving winds have been blowing from the east‐southeast, nearly the opposite direction (mean azimuth = 285° ± 15°). Atmospheric modeling generally predicts net annual sand transport from the east‐southeast at present, consistent with Perseverance regolith wind tail and orbital observations. The orientation of ventifact flutes thus suggests that they were formed under a different climate regime. Differences in orientations of recent and paleo‐wind indicators have been noted at other Mars landing sites and may result from major orbital/axial changes that can cause significant changes in atmospheric circulation. Orientation differences between modern and older wind direction indicators at Jezero are useful clues to the climate history of the region.

This is the first part of a two‐part paper. NASA's Mars 2020 Perseverance rover measured winds on the Jezero crater floor close to the delta of an ancient river. A mostly repeatable diurnal cycle was observed and presented two regimes: (a) a convective regime, from dawn to sunset, with average easterly to southeasterly winds, during which maximum wind speeds were measured, and (b) a nighttime regime with westerly‐northwesterly winds followed by a relatively calm period with highly variable wind directions as a function of sol and time of night. The timing and magnitude of the observed regimes are consistent with primary control by regional and local slope flows. Data suggest that the surface circulation at Jezero region in northern spring and summer is highly unaffected by large‐scale circulation except during particular periods in the diurnal cycle or generally during dust storms, which is supported by MarsWRF model simulations. Consequently, the observed seasonal variability was weak. However, sol‐to‐sol and seasonal variability were measured, most of it during certain nighttime periods. Traveling waves consistent with baroclinic instability were clearly observed in surface winds at L s ∼ 75°. The early MY36/2022A regional dust storm at L s ∼ 153° disturbed the wind patterns with changes suggesting enhanced tidal flows. After sunset, the dust storm also produced detectable gravity wave activity, increasing the mixing in the nighttime planetary boundary layer during storm conditions. Inferred wind directions from dust devil movies strongly suggest that prevailing winds continued to be slope‐driven during the late summer, fall and early winter seasons.

Wind speeds measured by the Mars 2020 Perseverance rover in Jezero crater were fitted as a Weibull distribution. InSight wind data acquired in Elysium Planitia were also used to contextualize observations. Jezero winds were found to be much calmer on average than in previous landing sites, despite the intense aeolian activity observed. However, a great influence of turbulence and wave activity was observed in the wind speed variations, thus driving the probability of reaching the highest wind speeds at Jezero, instead of sustained winds driven by local, regional, or large‐scale circulation. The power spectral density of wind speed fluctuations follows a power‐law, whose slope deviates depending on the time of day from that predicted considering homogeneous and isotropic turbulence. Daytime wave activity is related to convection cells and smaller eddies in the boundary layer, advected over the crater. The signature of convection cells was also found during dust storm conditions, when prevailing winds were consistent with a tidal drive. Nighttime fluctuations were also intense, suggesting strong mechanical turbulence. Convective vortices were usually involved in rapid wind fluctuations and extreme winds, with variations peaking at 9.2 times the background winds. Transient high wind events by vortex‐passages, turbulence, and wave activity could be driving aeolian activity at Jezero. We report the detection of a strong dust cloud of 0.75–1.5 km in length passing over the rover. The observed aeolian activity had major implications for instrumentation, with the wind sensor suffering damage throughout the mission, probably due to flying debris advected by winds.

Mastcam-Z is a multispectral, stereoscopic imaging investigation on the Mars 2020 mission’s Perseverance rover. Mastcam-Z consists of a pair of focusable, 4:1 zoomable cameras that provide broadband red/green/blue and narrowband 400-1000 nm color imaging with fields of view from 25.6° × 19.2° (26 mm focal length at 283 μrad/pixel) to 6.2° × 4.6° (110 mm focal length at 67.4 μrad/pixel). The cameras can resolve (≥ 5 pixels) ∼0.7 mm features at 2 m and ∼3.3 cm features at 100 m distance. Mastcam-Z shares significant heritage with the Mastcam instruments on the Mars Science Laboratory Curiosity rover. Each Mastcam-Z camera consists of zoom, focus, and filter wheel mechanisms and a 1648 × 1214 pixel charge-coupled device detector and electronics. The two Mastcam-Z cameras are mounted with a 24.4 cm stereo baseline and 2.3° total toe-in on a camera plate ∼2 m above the surface on the rover’s Remote Sensing Mast, which provides azimuth and elevation actuation. A separate digital electronics assembly inside the rover provides power, data processing and storage, and the interface to the rover computer. Primary and secondary Mastcam-Z calibration targets mounted on the rover top deck enable tactical reflectance calibration. Mastcam-Z multispectral, stereo, and panoramic images will be used to provide detailed morphology, topography, and geologic context along the rover’s traverse; constrain mineralogic, photometric, and physical properties of surface materials; monitor and characterize atmospheric and astronomical phenomena; and document the rover’s sample extraction and caching locations. Mastcam-Z images will also provide key engineering information to support sample selection and other rover driving and tool/instrument operations decisions.

The Mastcam-Z Camera is a stereoscopic, multispectral camera with zoom capability on NASA’s Mars-2020 Perseverance rover. The Mastcam-Z relies on a set of two deck-mounted radiometric calibration targets to validate camera performance and to provide an instantaneous estimate of local irradiance and allow conversion of image data to units of reflectance (R ∗ or I/F) on a tactical timescale. Here, we describe the heritage, design, and optical characterization of these targets and discuss their use during rover operations. The Mastcam-Z primary calibration target inherits features of camera calibration targets on the Mars Exploration Rovers, Phoenix and Mars Science Laboratory missions. This target will be regularly imaged during flight to accompany multispectral observations of the martian surface. The primary target consists of a gold-plated aluminum base, eight strong hollow-cylinder Sm 2 Co 17 alloy permanent magnets mounted in the base, eight ceramic color and grayscale patches mounted over the magnets, four concentric, ceramic grayscale rings and a central aluminum shadow post (gnomon) painted with an IR-black paint. The magnets are expected to keep the central area of each patch relatively free of Martian aeolian dust. The Mastcam-Z secondary calibration target is a simple angled aluminum shelf carrying seven vertically mounted ceramic color and grayscale chips and seven identical, but horizontally mounted ceramic chips. The secondary target is intended to augment and validate the calibration-related information derived from the primary target. The Mastcam-Z radiometric calibration targets are critically important to achieving Mastcam-Z science objectives for spectroscopy and photometric properties.

TRANSITION AT GALE CRATER. W. Rapin, G. Dromart, D. Rubin, L. Le Deit, S. Le Mouélic, O. Gasnault, G. Caravaca, N. Mangold, V. Fox, J.L. Dickson, B.L. Ehlmann, K. Herkenhoff, L.A. Edgar, R.B. Anderson, P. Pinet, S. Maurice, R.C. Wiens. IRAP, université de Toulouse, France, william.rapin@irap.omp.eu; Univ. Lyon, LGLTPE, France; University of California, Santa Cruz; LPG, CNRS-Univ. Nantes, France ; Caltech-JPL, Pasadena CA; Astrogeology Science Center, USGS, Flagstaff AZ; LANL.

The NASA Perseverance rover Mast Camera Zoom (Mastcam-Z) system is a pair of zoomable, focusable, multi-spectral, and color charge-coupled device (CCD) cameras mounted on top of a 1.7 m Remote Sensing Mast, along with associated electronics and two calibration targets. The cameras contain identical optical assemblies that can range in focal length from 26 mm ( $25.5^{\circ }\, \times 19.1^{\circ }\ \mathrm{FOV}$ ) to 110 mm ( $6.2^{\circ } \, \times 4.2^{\circ }\ \mathrm{FOV}$ ) and will acquire data at pixel scales of 148-540 μm at a range of 2 m and 7.4-27 cm at 1 km. The cameras are mounted on the rover’s mast with a stereo baseline of $24.3\pm 0.1$ cm and a toe-in angle of $1.17\pm 0.03^{\circ }$ (per camera). Each camera uses a Kodak KAI-2020 CCD with $1600\times 1200$ active pixels and an 8 position filter wheel that contains an IR-cutoff filter for color imaging through the detectors’ Bayer-pattern filters, a neutral density (ND) solar filter for imaging the sun, and 6 narrow-band geology filters (16 total filters). An associated Digital Electronics Assembly provides command data interfaces to the rover, 11-to-8 bit companding, and JPEG compression capabilities. Herein, we describe pre-flight calibration of the Mastcam-Z instrument and characterize its radiometric and geometric behavior. Between April 26 $^{th}$ and May 9 $^{th}$ , 2019, ∼45,000 images were acquired during stand-alone calibration at Malin Space Science Systems (MSSS) in San Diego, CA. Additional data were acquired during Assembly Test and Launch Operations (ATLO) at the Jet Propulsion Laboratory and Kennedy Space Center. Results of the radiometric calibration validate a 5% absolute radiometric accuracy when using camera state parameters investigated during testing. When observing using camera state parameters not interrogated during calibration (e.g., non-canonical zoom positions), we conservatively estimate the absolute uncertainty to be $<10\%$ . Image quality, measured via the amplitude of the Modulation Transfer Function (MTF) at Nyquist sampling (0.35 line pairs per pixel), shows $\mathrm{MTF}_{\mathit{Nyquist}}=0.26-0.50$ across all zoom, focus, and filter positions, exceeding the $>0.2$ design requirement. We discuss lessons learned from calibration and suggest tactical strategies that will optimize the quality of science data acquired during operation at Mars. While most results matched expectations, some surprises were discovered, such as a strong wavelength and temperature dependence on the radiometric coefficients and a scene-dependent dynamic component to the zero-exposure bias frames. Calibration results and derived accuracies were validated using a Geoboard target consisting of well-characterized geologic samples.

The Curiosity rover is exploring Hesperian-aged stratigraphy in Gale crater, Mars, where a transition from clay-bearing units to a layered sulfate-bearing unit has been interpreted to represent a major environmental transition of unknown character. We present the first description of key facies in the sulfate-bearing unit, recently observed in the distance by the rover, and propose a model for changes in depositional environments. Our results indicate a transition from lacustrine mudstones into thick aeolian deposits, topped by a major deflation surface, above which strata show architectures likely diagnostic of a subaqueous environment. This model offers a reference example of a depositional sequence for layered sulfate-bearing strata, which have been identified from orbit in other locations globally. It differs from the idea of a monotonic Hesperian climate change into long-term aridity on Mars and instead implies a period characterized by multiple transitions between sustained drier and wetter climates.

Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.

We assessed dust coverage on the Mars Science Laboratory Mars Hand Lens Imager (MAHLI) and Alpha Particle X-Ray Spectrometer (APXS) calibration targets from 14 MAHLI images acquired at <100 mu m/pixel, between Mars Science Laboratory Curiosity rover sols 34 and 2248, in order to place constraints on dust accumulation and removal on two endmember orientations (vertical and horizontal). Dust coverage was estimated by (1) determining reflectance ranges for image pixels covered by dust; (2) using the ratio of calibrated MAHLI red band data to blue band data as a proxy for the concentration of dust on the calibration target; and (3) manually counting dust-covered pixels in representative areas of the MAHLI calibration target. The results of each method are consistent within uncertainties, but the reflectance method provided the most efficient and effective way to measure dust cover on each target. Mean and median dust coverage is similar to 4.7% and 3.9% for the MAHLI target, 9.4% and 8.9% for the APXS target, and 51.9% and 63.4% for the REMS UV sensor. Maximum dust coverage (during the dust storm) is 49% and 42% for the MAHLI and APXS calibration targets respectively, and 80% for the REMS UV sensor. In modeling dust accumulation and removal, the best fit for the MAHLI and APXS targets is one that assumes 2-4% dust removal per sol and 20-40% efficiency in collection, while for the REMS UV sensor, it is one that assumes near 0 removal and 7% of nominal accumulation. Results indicate that the vertically-mounted MAHLI and APXS targets accumulated less dust overall during the mission than horizontally-mounted hardware such as the REMS UV sensor; this was true even during the 2018 global dust event. In addition, while the vertical orientation did not protect the targets from dust deposition during that event, dust removal following the event was more effective on these targets than on horizontally-mounted hardware. Because conditions cannot be monitored continuously, these studies cannot fully discriminate among the potential causes of this dust removal. However, the results suggest that vertical mounting is a reasonable dust mitigation strategy for hardware for which short-term dust accumulation is not a risk factor.