A multi‐instrument study of the regolith of Jezero crater floor units by the Perseverance rover has identified three types of regolith: fine‐grained, coarse‐grained, and mixed‐type. Mastcam‐Z, Wide Angle Topographic Sensor for Operations and eNgineering, and SuperCam Remote Micro Imager were used to characterize the regolith texture, particle size, and roundedness where possible. Mastcam‐Z multispectral and SuperCam laser‐induced breakdown spectroscopy data were used to constrain the composition of the regolith types. Fine‐grained regolith is found surrounding bedrock and boulders, comprising bedforms, and accumulating on top of rocks in erosional depressions. Spectral and chemical data show it is compositionally consistent with pyroxene and a ferric‐oxide phase. Coarse‐grained regolith consists of 1–2 mm well‐sorted gray grains that are found concentrated around the base of boulders and bedrock, and armoring bedforms. Its chemistry and spectra indicate it is olivine‐bearing, and its spatial distribution and roundedness indicate it has been transported, likely by saltation‐induced creep. Coarse grains share similarities with the olivine grains observed in the Séítah formation bedrock, making that unit a possible source for these grains. Mixed‐type regolith contains fine‐ and coarse‐grained regolith components and larger rock fragments. The rock fragments are texturally and spectrally similar to bedrock within the Máaz and Séítah formations, indicating origins by erosion from those units, although they could also be a lag deposit from erosion of an overlying unit. The fine‐ and coarse‐grained types are compared to their counterparts at other landing sites to inform global, regional, and local inputs to regolith formation within Jezero crater. The regolith characterization presented here informs the regolith sampling efforts underway by Perseverance.

A suite of high resolution cameras onboard the Mars Science Laboratory (MSL) Curiosity rover have provided an unparalleled look at active aeolian processes on Mars, including within the first active dune field explored on another planet, the Bagnold Dunes. Here we present results from a subset of MSL's repeat imaging (“change detection”) experiments with temporal resolutions sufficient to probe the diurnal variability in winds within Gale crater. Images reveal that saltation is a near‐daily phenomenon during southern summer, with repeatable diurnal circulation patterns producing steady impact ripple migration toward the west/southwest. Nighttime fluxes are inferred to be ∼four times larger than daytime fluxes, consistent with predictions from the MarsWRF model of multiple periods of enhanced wind between sunset and sunrise. Multiple factors are likely facilitating saltation at this time: (a) time‐averaged nighttime winds have a higher degree of variance (i.e., higher peak friction speeds) than daytime winds, (b) interactions between regional Hadley flows and local, thermally driven slope winds cause increased turbulence at night, and (c) relatively higher atmospheric density produces correspondingly higher shear stresses and decreases critical thresholds. Observations of sand transport at a range of spatiotemporal scales (down to scale of individual particles moving on the timescale of seconds) support the idea that bedform migration is driven by intermittent, low‐flux saltation events when winds fluctuate between canonical impact and fluid thresholds. Yet, whereas gustiness may play a role in initiating transport, saltation is found to be highly predictable on diurnal timescales and is only stochastic on the shortest timescales characteristic of turbulent fluctuations in wind.

On Mars, near the equator, much of the terrain in Gale Crater consists of bedrock outcrops separated by relatively smooth, uniform regolith surfaces. In scattered sites, however, distinct patterns—in the form and texture of the ground surface—contrast sharply with the typical terrain and with eolian bedforms. This paper focuses on these diverse, intriguing ground patterns. They include ∼1 to >10 m‐long linear disruptions of uniform regolith surfaces, alignments, and other arrangements of similar‐sized rock fragments and shallow, ∼0.1 m‐wide sandy troughs 1–10 m in length. Similar features were recognized early in the Mars Science Laboratory (MSL) mission, but they received only limited attention until Curiosity, the MSL rover, encountered striking examples in the Glen Torridon region. Herein, the ground patterns are illustrated with rover images. Potential mechanisms are briefly discussed in the context of the bedrock composition and atmospheric conditions documented by Curiosity. The evidence suggests that the patterns are active forms of spontaneous granular organization. It leads to the hypothesis that the patterns arise and develop from miniscule, inferred cyclic expansion and contraction of the bedrock and regolith, likely driven by oscillating transfers of energy and moisture between the atmosphere and the terrain. The hypothesis has significant implications for studies of contemporary processes on Mars on both sides of the atmosphere‐lithosphere interface. The ground patterns, as well as ripples and dunes formed by the wind, constitute remarkable extra‐terrestrial examples of granular self‐organization, complex phenomena well known in diverse systems on Earth.

Perseverance's Mastcam-Z instrument provides high-resolution stereo and multispectral images with a unique combination of spatial resolution, spatial coverage, and wavelength coverage along the rover's traverse in Jezero crater, Mars. Images reveal rocks consistent with an igneous (including volcanic and/or volcaniclastic) and/or impactite origin and limited aqueous alteration, including polygonally fractured rocks with weathered coatings; massive boulder-forming bedrock consisting of mafic silicates, ferric oxides, and/or iron-bearing alteration minerals; and coarsely layered outcrops dominated by olivine. Pyroxene dominates the iron-bearing mineralogy in the finegrained regolith, while olivine dominates the coarse-grained regolith. Solar and atmospheric imaging observations show significant intra- and intersol variations in dust optical depth and water ice clouds, as well as unique examples of boundary layer vortex action from both natural (dust devil) and Ingenuity helicopter-induced dust lifting. High-resolution stereo imaging also provides geologic context for rover operations, other instrument observations, and sample selection, characterization, and confirmation.

This study reports on the physical properties and geochemistry of aeolian bedform grains along the Curiosity rover traverse in Gale crater from Vera Rubin Ridge to the Sands of Forvie (Sols 1902–2995), and includes comparisons to results made earlier in the mission. Volumetrically, <150 μm grains dominate active aeolian bedforms in the study area, similar to previous findings elsewhere at Gale crater and at other locations on Mars. Coarser grains, up to 2.9 mm long, are present on larger active bedforms. The larger 1–3 mm active grains commonly are reddish or whitish in color and irregular in shape, suggesting erosion of local bedrock as sources. One inactive megaripple had a surface of dust‐covered 2–15 mm grains, with smaller <150 μm grains between and within the bedform interior. Geochemical measurements show element concentrations vary according to position on the bedform, sand activity, and grain contributions from local bedrock. A strong positive correlation between Mg and Ni is identified on active bedform surfaces, with the highest Ni always corresponding to ripple crests where the coarsest gray and clear grains were commonly found. There is also a correlation between Ti and Cr for the majority of active sands, with the finer active sands in ripple troughs and sand patches having the greatest number of red grains and highest Cr concentrations. These results show the smaller scale physical properties and geochemistry of several types of aeolian bedforms on Mars formed under current and ancient environments.

The Mars Science Laboratory rover, Curiosity, explored the clay mineral-bearing Glen Torridon region for 1 Martian year between January 2019 and January 2021, including a short campaign onto the Greenheugh pediment. The Glen Torridon campaign sought to characterize the geology of the area, seek evidence of habitable environments, and document the onset of a potentially global climatic transition during the Hesperian era. Curiosity roved 5 km in total throughout Glen Torridon, from the Vera Rubin ridge to the northern margin of the Greenheugh pediment. Curiosity acquired samples from 11 drill holes during this campaign and conducted the first Martian thermochemolytic-based organics detection experiment with the Sample Analysis at Mars instrument suite. The lowest elevations within Glen Torridon represent a continuation of lacustrine Murray formation deposits, but overlying widespread cross bedded sandstones indicate an interval of more energetic fluvial environments and prompted the definition of a new stratigraphic formation in the Mount Sharp group called the Carolyn Shoemaker formation. Glen Torridon hosts abundant phyllosilicates yet remains compositionally and mineralogically comparable to the rest of the Mount Sharp group. Glen Torridon samples have a great diversity and abundance of sulfur-bearing organic molecules, which are consistent with the presence of ancient refractory organic matter. The Glen Torridon region experienced heterogeneous diagenesis, with the most striking alteration occurring just below the Siccar Point unconformity at the Greenheugh pediment. Results from the pediment campaign show that the capping sandstone formed within the Stimson Hesperian aeolian sand sea that experienced seasonal variations in wind direction.

Gale crater, the field site for NASA's Mars Science Laboratory Curiosity rover, contains a diverse and extensive record of aeolian deposition and erosion. This study focuses on a series of regularly spaced, curvilinear, and sometimes branching bedrock ridges that occur within the Glen Torridon region on the lower northwest flank of Aeolis Mons, the central mound within Gale crater. During Curiosity's exploration of Glen Torridon between sols ∼2300-3080, the rover drove through this field of ridges, providing the opportunity for in situ observation of these features. This study uses orbiter and rover data to characterize ridge morphology, spatial distribution, compositional and material properties, and association with other aeolian features in the area. Based on these observations, we find that the Glen Torridon ridges are consistent with an origin as wind-eroded bedrock ridges, carved during the exhumation of Mount Sharp. Erosional features like the Glen Torridon ridges observed elsewhere on Mars, termed periodic bedrock ridges (PBRs), have been interpreted to form transverse to the dominant wind direction. The size and morphology of the Glen Torridon PBRs are consistent with transverse formative winds, but the orientation of nearby aeolian bedforms and bedrock erosional features raise the possibility of PBR formation by a net northeasterly wind regime. Although several formation models for the Glen Torridon PBRs are still under consideration, and questions persist about the nature of PBR-forming paleowinds, the presence of PBRs at this site provides important constraints on the depositional and erosional history of Gale crater.

On Mars, large aeolian ripples with wavelengths typically 1–3 m but lacking very coarse sand at crests have been encountered by rovers and observed from orbit. These bedforms have no terrestrial counterpart and several hypotheses for origins have been proposed. This work reports results of Computational Fluid Dynamics (CFD) experiments with ANSYS Fluent under terrestrial and Martian boundary layer conditions, using the k − ω SST turbulence model to evaluate shear stress along a topographic profile of large Martian ripples at different boundary layer wind speeds. Results indicate that, compared with Earth conditions: (1) boundary‐layer flow along large ripples under Martian conditions is less turbulent due to higher kinematic viscosity; (2) reverse‐flow vortex regions from crests at ripple lee flanks are larger; and (3) shear stresses at crests of large ripples are relatively low, so ripple flattening is less likely at high wind speeds. These results indicate Martian ripples formed by the saltation impact splash mechanism should be less constrained by shear stress effects limiting growth of exposed ripple crests, because the low‐density Martian atmosphere applies relatively low wind‐related shear stress to ripple surfaces. Other origins for the large Martian ripples are not excluded, however. On Earth, very large ripples with crests unprotected by very coarse grains do not develop due to higher wind‐related shear stresses.

Abstract In this contribution we report measurements and interpretations of aeolian abrasion features observed along the Mars Science Laboratory rover traverse at Gale Crater on Mars. Aeolian abrasion of surface rocks has been documented by most missions that have landed on Mars, but attention has largely focused on relatively resistant rocks that display ventifact morphologies well‐known from Earth. The current study instead emphasizes abrasion features developed on mudstone surfaces, because aeolian abrasion textures are very common in the mudstone‐dominated Murray Formation at Gale Crater. These abrasion textures have been observed over a wide area, and they allow deductions about dominant past wind regimes that differ from those observed at present. On Earth, aeolian abrasion features in mudstone outcrops have minimal preservation potential because of the susceptibility of mudstones to moisture and aqueous erosion, even in dominantly arid surface environments. Because of this there is no literature on potential terrestrial analogs. In order to better understand aeolian abrasion morphologies in mudstones on Mars, laboratory experiments were conducted that exposed a range of mudstone samples and rock simulant samples to wind‐driven sand for periods of up to four months. These experiments produced a range of aeolian abrasion textures (‘wind tails’, fluting, differential ‘etching’ of laminae, stalks and pedestals) that can serve as analogs for features in the Murray Formation, increasing our confidence regarding aeolian origins for these and the deductions of formative, sand‐driving wind azimuths. Orientations of aeolian abrasion textures along the Mars Science Laboratory traverse were compared with active ripple orientations in rover images, and with previous analyses of orbital images of the study area, in order to evaluate whether the current, complex wind environment can explain the abrasion orientations observed in rover images, or if the abrasion record might also contain signatures of past wind regimes that differed from those of the present. Results show relatively coherent patterns of airflow and sand movement that vary in accordance with factors like local topography and upwind availability of sand for abrasion. Wind events blowing southwest that are primarily responsible for southwest migration of the Bagnold Dunes have also caused bedrock abrasion of similar orientation between these dunes. Less effective wind events (from an abrasion standpoint) blowing south‐southeast have broadly affected bedrock exposures elsewhere across the Mars Science Laboratory landing site away from the Bagnold Dunes. A notable exception are northeast abrasion textures on the more erosion‐resistant sandstones of the Naukluft Plateau. The latter are consistent with one of two abrasion directions measured in previous studies, prior to the rover's arrival at the Murray Formation mudstones, and probably reflect the preservation of an ancient sand‐driving wind regime that differs from that of the present.

Orbiter-based observations have demonstrated that active aeolian environments are ubiquitous across Mars. Here we examine one such environment, the Bagnold Dune Field in Gale crater, with repeat imaging campaigns conducted from Curiosity during southern summer. Images reveal widespread migration of aeolian impact ripples (up to 2.8 cm/sol), which is in stark contrast to the inactivity of similar bedforms during southern winter. The winds responsible for steady southwestward migration of ripples are consistent with predictions of regional-scale flows that enter the crater from the north and interact with the topography of Mount Sharp but are not fully representative of all dune-forming winds. Inferred friction speeds of 1.5 m/s needed to explain mobilization of bedforms are likely not being achieved, and thus, a majority of sediment transport may be taking place at subthreshold conditions. This hypothesis is further supported by sand flux estimates that suggest a low saltation flux environment within the dune field. Plain Language Summary A wealth of orbital images have revealed that wind is actively moving sand on the surface of Mars; landed instruments enable a closer look at these processes. Images acquired during southern summer by the Curiosity rover in Gale crater revealed high levels of wind activity, in contrast to previous imaging done during southern winter. A majority of ripple migration occurs toward the southwest, with ripples moving up to 2.8 cm per day. These findings are consistent with models that predict southern summer to be the windiest season at this location on Mars, with strong regional winds flowing over the northern crater rim and causing strong southwestward flow along the floor of the crater in the vicinity of the rover. Despite the fact that bedforms are active, models do not predict that the wind should be strong enough to initiate motion, which challenges our understanding of the physics of sediment transport under Martian conditions.

We measured sand sizes and shapes on diverse eolian bedforms in Gale crater to help constrain models of eolian sediment transport on Mars. All grains are subangular to rounded with circularities of similar to 0.93-0.97, indicating an extensive abrasion history. There are two types of active bedforms based on grain size: (1) ripples composed of 50- to 150-mu m grains and (2) ripples that also include 250- to 500-mu m grains along their crests, in some cases with small amounts of even coarser grains (up to 1.4 mm). The smallest grain sizes (50-150 mu m) are volumetrically the most abundant at all active bedforms. Inactive bedforms have surfaces of 350- to 2,2000-mu m grains with finer-grained interiors, consistent with observations made by rovers at other landing sites. Grains coarser than similar to 300 mu m are less prone to mobilization driven by smaller saltating grains, making bedforms with concentrations of coarser grains more susceptible to surface stabilization and inactivity. Plain Language Summary We used microscopic images taken by a camera on the Curiosity rover at Mars to measure the shapes and sizes of sand grains. There are two types of active ripples that we identified based upon grain size: those that have grain sizes between 50 and 150 microns and those with coarser grains between 250 and 500 microns. Most of the grains on the active Bagnold dunes are very fine sand, except at the crests of larger ripples where the grains tend to be larger. The grains are circular and rounded, indicating that they have experienced an extensive abrasion history. Inactive ripples have coarser grains (350-2,000 mu m) armoring finer interior grains, some of which could be locally derived from the Stimson sandstone and Murray Formation outcrops. On Earth, the physical properties of grains partly control bedform morphology and are closely linked with mobility. Because these same principles are expected on Mars, it is important to know sand grain size and shape distributed across diverse ripple morphologies to help constrain models of martian bedform formation.

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.

A high density of REMS wind measurements were collected in three science investigations during MSL's Bagnold Dunes Campaign, which took place over ~80 sols around southern winter solstice (Ls~90°) and constituted the first in situ analysis of the environmental conditions, morphology, structure, and composition of an active dune field on Mars. The Wind Characterization Investigation was designed to Available online 14 December 2016 fully characterize the near-surface wind field just outside the dunes and confirmed the primarily upslope/downslope flow expected from theory and modeling of the circulation on the slopes of Aeolis Mons in this season. The basic pattern of winds is 'upslope' (from the northwest, heading up Aeolis Mons) during the daytime (~09:00-17:00 or 18:00) and 'downslope' (from the southeast, heading down Aeolis Mons) at night (~20:00 to some time before 08:00). Between these times the wind rotates largely clockwise, giving generally westerly winds mid-morning and easterly winds in the early evening. The timings of these direction changes are relatively consistent from sol to sol; however, the wind direction and speed at any given time shows considerable intersol variability. This pattern and timing is similar to predictions from the MarsWRF numerical model, run at a resolution of ~490 m in this region, although the model predicts the upslope winds to have a stronger component from the E than the W, misses a wind speed peak at ~09:00, and under-predicts the strength of daytime wind speeds by ~2-4 m/s. The Namib Dune Lee Investigation reveals 'blocking' of northerly winds by the dune, leaving primarily a westerly component to the daytime winds, and also shows a broadening of the 1 Hz wind speed distribution likely associated with lee turbulence. The Namib Dune Side Investigation measured primarily daytime winds at the side of the same dune, in support of aeolian change detection experiments designed to put limits on the saltation threshold, and also appears to show the influence of the dune body on the local flow, though less clearly than in the lee. Using a vertical grid with lower resolution near the surface reduces the relative strength of nighttime winds predicted by MarsWRF and produces a peak in wind speed at ~09:00, improving the match to the observed diurnal variation of wind speed, albeit with an offset in magnitude. The annual wind field predicted using this grid also provides a far better match to observations of aeolian dune morphology and motion in the Bagnold Dunes. However, the lower overall wind speeds than observed and disagreement with the observed wind direction at ~09:00 suggest that the problem has not been solved and that alternative boundary layer mixing schemes should be explored which may result in more mixing of momentum down to the near-surface from higher layers. These results demonstrate a strong need for in situ wind data to constrain the setup and assumptions used in numerical models, so that they may be used with more confidence to predict the circulation at other times and locations on Mars.