Recent studies using HiRISE and CTX imagery show that fan-shaped deposits are widespread especially across the walls of craters on Mars and likely formed during the Hesperian and Amazonian periods. Remote imagery and topographic analyses suggest that they may have been produced by both fluvial and debris-flow processes and are generally distinct from deltaic deposits such as those in Jezero. Curiosity rover-based observations of the deeply eroded deposits of the Gediz Vallis Ridge (GVR), lying at the base of Aeolis Mons (Mt. Sharp), now provide our first cross-sectional observation of a steep, central peak-based Martian fan, revealing episodic deposition by debris flows, and reworking by fluvial processes, and likely fluvial sheetfloods. The fan remnants today rest on top of the Stimson formation, a lithified aeolian sandstone that mantles the Greenheugh pediment. Above the Stimson is a discontinuous, fine-grained (<= gravel size), Basal unit with decimeter-scale bedding that is concordant with the top of the Stimson. The unit reaches a maximum observable thickness of 15 m and is unconformably onlapped by stratified gravel and boulder deposits. Discontinuous layering within these deposits ranges in thickness from 0.25 to 3 m and exhibits a mean slope of 7% oriented parallel to the ridge axis, which is much gentler than the slope of the basal contact. At progressively higher elevations, five depositional packages are exposed. Each package is composed of two facies whose frequency and lateral extent differ: 1) a light-toned, boulder-rich coarse facies, typically matrix-supported, with scattered erosionally resistant dark-toned gravel and boulders, and 2) a dark-toned gravel and boulder facies, typically clast-supported. Both facies have median grain sizes of about 180 mm and host 1-3 m boulders scattered throughout. The light-toned strata are interpreted as debris flow deposits. The dark-toned strata are interpreted to be fluvial, probably derived from surface runoff that concentrated dark clasts from the light-toned unit into channels and sheetflood deposits while disaggregating the weaker light-toned sediment during transport. The gentle slopes of these deposits indicate that the depocenter back-stepped up the steep underlying pediment surface, and probably formed the core of fan that may have extended as much as 10 km downslope, likely in the late Hesperian or early Amazonian. Most of the fan may have been composed of the light-toned sediment highly erodible by wind, leading to a near complete removal of the fan deposit after the cessation of fan construction. Stratigraphic differences in the five packages suggest significant changes in the magnitude and frequency of surface runoff and sediment supply likely reflecting variable climate conditions. Reconstructed fan sediment volume estimates indicate that at least many tens of meters (and likely much more) of precipitation-generating runoff from Mt. Sharp were needed to build the fan, and this involved thousands of runoff events. This variability supports proposals based on orbiter data that Martian fans are characterized by mixtures of debris flow and fluvial deposits and that fan development was episodic, rather than a single pulse. The GVR fan records one of the last significant hydrogeomorphic phases in Gale and likely the youngest observed in situ by Curiosity.

Evidence of paleo-rivers, fans, deltas, lakes, and channel networks across Mars has prompted much debate about what climate conditions would permit the formation of these surface water derived features. Pediments, gently sloping erosional surfaces of low relief developed in bedrock, have also been identified on Mars. On Earth, these erosional landforms, often thought to be created by overland flow and shallow channelized runoff, are typically capped by fluvial sediments, and thus in exceptionally arid regions, pediments are interpreted to record past wet periods. Here we document the Greenheugh pediment in Gale crater, exploiting the observational capability of the Curiosity rover. The absence of a fluvial cap suggests that the pediment was likely cut by wind erosion, not fluvial processes. The pediment was then buried by an aeolian deposit (Stimson sandstone) that mantled the lower footslopes of Aeolis Mons (informally known as Mt. Sharp). This burial terminated active wind erosion, preserving the pediment surface (as an angular unconformity). Groundwater was present prior-to, during, and shortly after Stimson deposition, perhaps contributing to lithification and certainly to early diagenesis. Post lithification, wind erosion first cut canyons in the northern most footslopes (north of Vera Rubin ridge). Unlithified gravels were deposited in these canyons, likely due to runoff from Mt. Sharp. Boulder-rich fluvial and debris flow deposits built a > 70 m thick sequence (Gediz Vallis ridge) on the southern Greenheugh pediment. Continued wind erosion left elevated patches of gravel on the northern footslopes, and exposure age dating shows that erosion essentially ceased before 1 Ga (but possibly much earlier). Erosion to the south led to emergence of Vera Rubin ridge, retreat of the Greenheugh pediment, and the formation of Glen Torridon valley. Hence, this footslope environment of Mt. Sharp records climate-driven periods of wind erosion, aeolian deposition (and groundwater activity), surface runoff and sediment deposition, followed by further significant wind erosion that declined to present very slow rates. This likely occurred during the late Hesperian and possibly into the Amazonian.

The Mars Science Laboratory Curiosity rover has monitored the Martian environment in Gale crater since landing in 2012. This study reports the record of optical depth derived from visible and near-infrared images of the Sun. Aerosol optical depth, which is mostly due to dust but also includes ice, dominates the record, with gas optical depth too small to measure. The optical depth record includes the effects of regional dust storms and one planet-encircling dust event, showing the expected peaks during southern spring and summer and relatively lower and more stable optical depth in fall and winter. The measurements show that there is a seasonally varying diurnal change in dust load, with the optical depth peaking in the morning during southern spring and summer, correlated with thermotidal pressure changes. However, there was no systematic diurnal change during autumn and winter, except after one regional storm. There were indications that the dust was relatively enhanced at high altitudes during high-optical-depth periods and that high-altitude ice was significant during winter. The observations did not provide much information about particle size or composition, but they were consistent with a smaller particle size after aphelion (in southern winter). No scattering halos were seen in associated sky images, even when there was visual evidence of ice hazes or clouds, which suggests small or amorphous ice particles. Unexpectedly, the measurement campaign revealed that the cameras collected saltating sand in their sunshades 1.97 m above the surface. As a result, the measurement strategy had to be adjusted to avoid high-elevation imaging to avoid sand covering the optics.

AbstractWater and carbon dioxide each form mesospheric clouds on Mars. At such altitudes (40–100 km), clouds may remain sunlit for part of the night. We describe a previously unreported, visually spectacular season of iridescent, noctilucent clouds visible in early southern autumn from the Curiosity rover's site in Gale crater. Ice nucleation begins near sunset with a narrow range of particle sizes, and the ice aerosols grow and precipitate. The iridescence, visible through three‐color imaging, arises from locally uniform particle sizes resulting from similar growth histories. Colorful fall streaks show the clouds evolving, and a scattering corona shows size uniformity over large areas. The terminator was observed on the clouds, allowing the determination of cloud altitudes and a likely CO2 composition. This is the first observation of particle size variations within individual Martian clouds, allowing a new probe of Martian cloud physics.

Wave modeling and analysis of sedimentary structures were used to evaluate whether four examples of symmetrical, reversing, or straight‐crested bedforms in Gale crater sandstones are preserved wave ripples; deposition by waves would demonstrate that the lake was not covered by ice at that time. Wave modeling indicates that regardless of atmospheric density, winds that exceeded the threshold of aeolian sand transport could have generated waves capable of producing nearshore wave ripples in most grain sizes of sand. Reversing 3‐m‐wavelength bedforms in the Kimberley formation are interpreted not as wave ripples but rather as large aeolian ripples that formed in an atmosphere approximately as thin as at present. These exhumed bedforms define many of the ridges at outcrops that appear striated in satellite images. At Kimberley these bedforms demonstrably underlie and therefore predate subaqueous beds, suggesting that a thin atmosphere existed at least temporarily before subaqueous deposition ceased in the crater. The other three candidate wave ripples (Square Top, Hunda, and Voe) are consistent with modeled waves, but other origins cannot be excluded. The predominance of flat‐laminated (non‐rippled) beds in the lacustrine Murray formation suggests that some aspect of the lake was not conducive to formation or preservation of recognizable wave ripples. Water depths may generally have been too deep, lakebed sediment may have been too fine‐grained, the lake may have been smaller than modeled, or the lake may have been covered by ice.

Two >130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.

Dataset accompanying the publication titled "New Craters on Mars: An Updated Catalog" by I. J. Daubar et al., published by Journal of Geophysical Research: Planets in 2022. For more details, see that publication.

R. M. E. Williams, M. C. Malin, K. S. Edgett, R. C. Wiens, R. A. Yingst, K. M. Stack, S. Gupta, E. Heydari, J. Bridges, V. Sautter, A. Cousin, and O. Gasnault. Planetary Science Institute, Tucson, AZ, williams@psi.edu, Malin Space Science Systems, San Diego, CA, LANL, Los Alamos, NM, JPL/Caltech, Pasadena, CA, Imperial College, London, UK, Jackson State University, Jackson, MS, University of Leicester, UK, IMPMC, Sorbonne Université, Paris, France, IRAP, Toulous, France.

Introduction: Since landing at Gale crater in August, 2012, the Mars Science Laboratory rover Curiosity has observed present and past aeolian activity as recorded by sand grain motion, actively migrating aeolian bedforms, and aeolian abrasion textures and morphologies of large rocks and bedrock surfaces (ventifacts). Modern dune forms record a bidirectional wind regime [1, 2], that moves sediment in southwesterly (225) and southeasterly (150) directions. Observations early in the rover traverse of abrasion facets, lineations, and fluting in rocks also suggest a bimodal wind regime with one dominant airflow direction towards the southeast, and another to the northeast [2]. Whereas the former direction matches the modern dune observations [1], the latter does not and might record an earlier wind regime [2]. These observations suggest the potential of surface rocks to carry an imprint of past wind regimes in Gale crater which may help us better understand the excavation of the crater fill, leading to present day topography. Because mudstones are easily abraded to form “wind tails” in experiments [3], and analogous features were observed in the Sheepbed mudstone [4] and in the first exposures of the Murray formation (Fig. 1), we examined the distribution of wind abrasion features in the Murray formation through Sol 1742 of the MSL rover traverse.

Lees, Leslie Keely, Timothy J. Parker and Michael Malin, SGT , NASA Ames Research Center, MS 2453, Moffett Field, CA, USA, Carnegie Mellon University, Jet Propulsion Lab, Malin Science Space Systems (ara.nefian@nasa.gov) This paper presents a fully automatic rover localization system suitable for autonomous planetary exploration in the absence of Global Positioning System (GPS) infrastructure. The method presented in this paper determines the best rover location through matching between the terrain seen by the onboard rover stereo camera system and a pre-existing 3D orbital map. The system is tested on data retrieved from the Mars Science Lab (MSL) mission and uses a human in the loop localization solution as ground truth. Experimental results show the system presented here can localize the rover 87% of the time within 10m of the ground truth solution.

The Mars Science Laboratory Mast camera and Descent Imager investigations were designed, built, and operated by Malin Space Science Systems of San Diego, CA. They share common electronics and focal plane designs but have different optics. There are two Mastcams of dissimilar focal length. The Mastcam‐34 has an f/8, 34 mm focal length lens, and the M‐100 an f/10, 100 mm focal length lens. The M‐34 field of view is about 20° × 15° with an instantaneous field of view (IFOV) of 218 μrad; the M‐100 field of view (FOV) is 6.8° × 5.1° with an IFOV of 74 μrad. The M‐34 can focus from 0.5 m to infinity, and the M‐100 from ~1.6 m to infinity. All three cameras can acquire color images through a Bayer color filter array, and the Mastcams can also acquire images through seven science filters. Images are ≤1600 pixels wide by 1200 pixels tall. The Mastcams, mounted on the ~2 m tall Remote Sensing Mast, have a 360° azimuth and ~180° elevation field of regard. Mars Descent Imager is fixed‐mounted to the bottom left front side of the rover at ~66 cm above the surface. Its fixed focus lens is in focus from ~2 m to infinity, but out of focus at 66 cm. The f/3 lens has a FOV of ~70° by 52° across and along the direction of motion, with an IFOV of 0.76 mrad. All cameras can acquire video at 4 frames/second for full frames or 720p HD at 6 fps. Images can be processed using lossy Joint Photographic Experts Group and predictive lossless compression.

The NASA Curiosity rover Mast Camera (Mastcam) system is a pair of fixed‐focal length, multispectral, color CCD imagers mounted ~2 m above the surface on the rover's remote sensing mast, along with associated electronics and an onboard calibration target. The left Mastcam (M‐34) has a 34 mm focal length, an instantaneous field of view (IFOV) of 0.22 mrad, and a FOV of 20° × 15° over the full 1648 × 1200 pixel span of its Kodak KAI‐2020 CCD. The right Mastcam (M‐100) has a 100 mm focal length, an IFOV of 0.074 mrad, and a FOV of 6.8° × 5.1° using the same detector. The cameras are separated by 24.2 cm on the mast, allowing stereo images to be obtained at the resolution of the M‐34 camera. Each camera has an eight‐position filter wheel, enabling it to take Bayer pattern red, green, and blue (RGB) “true color” images, multispectral images in nine additional bands spanning ~400–1100 nm, and images of the Sun in two colors through neutral density‐coated filters. An associated Digital Electronics Assembly provides command and data interfaces to the rover, 8 Gb of image storage per camera, 11 bit to 8 bit companding, JPEG compression, and acquisition of high‐definition video. Here we describe the preflight and in‐flight calibration of Mastcam images, the ways that they are being archived in the NASA Planetary Data System, and the ways that calibration refinements are being developed as the investigation progresses on Mars. We also provide some examples of data sets and analyses that help to validate the accuracy and precision of the calibration.