The Mars 2020 Perseverance rover landing site is located within Jezero crater, a
∼
50
km
diameter impact crater interpreted to be a Noachian-aged lake basin inside the western edge of the Isidis ...impact structure. Jezero hosts remnants of a fluvial delta, inlet and outlet valleys, and infill deposits containing diverse carbonate, mafic, and hydrated minerals. Prior to the launch of the Mars 2020 mission, members of the Science Team collaborated to produce a photogeologic map of the Perseverance landing site in Jezero crater. Mapping was performed at a 1:5000 digital map scale using a 25 cm/pixel High Resolution Imaging Science Experiment (HiRISE) orthoimage mosaic base map and a 1 m/pixel HiRISE stereo digital terrain model. Mapped bedrock and surficial units were distinguished by differences in relative brightness, tone, topography, surface texture, and apparent roughness. Mapped bedrock units are generally consistent with those identified in previously published mapping efforts, but this study’s map includes the distribution of surficial deposits and sub-units of the Jezero delta at a higher level of detail than previous studies. This study considers four possible unit correlations to explain the relative age relationships of major units within the map area. Unit correlations include previously published interpretations as well as those that consider more complex interfingering relationships and alternative relative age relationships. The photogeologic map presented here is the foundation for scientific hypothesis development and strategic planning for Perseverance’s exploration of Jezero crater.
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.
Key Points
The Mars Descent Imager, an f/3 9.7 mm, 2 M pixel color camera operated autonomously during landing taking a descent video at 4 frames/second
Mastcam‐34 f/8, 34 mm camera takes <1600 × 1200 pixel images in broad and narrowband color over a field 20° × 15° at a scale of 218 μrad/pixel
Mastcam‐100 f/10, 100 mm, f/10 takes <1600 × 1200 pixel images in broad and narrowband color over a field 6.8° × 5.1° at 74 μrad/pixel scale
Plain Language Summary
Paper describes the Mast cameras and Descent Imager on the Mars Science Laboratory Curiosity rover. Cameras take 2 megapixel color images that can be compressed in both JPEG lossy and predictive lossless format. One of the two Mastcams has a 34 mm lens, equivalent to a consumer camera 35 mm lens, and the other has a 100 mm lens, similar to consumer camera telephoto lens. The descent imager has a very wide angle lens (~90°) and takes wide angle pictures. The Mast cameras are mounted on an azimuth elevation mast so they can scan around the rover and into the sky. The Descent camera always points down. The Mast cameras have different filters to allow for scientific color imaging as well as standard color imaging as performed by consumer cameras.
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 ...~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‐μm grains and (2) ripples that also include 250‐ to 500‐μm 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 μm) are volumetrically the most abundant at all active bedforms. Inactive bedforms have surfaces of 350‐ to 2,000‐μm grains with finer‐grained interiors, consistent with observations made by rovers at other landing sites. Grains coarser than ~300 μm 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 μm) 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.
Key Points
Sand grains on eolian bedforms on Mars vary in size and shape depending upon whether the bedform is active or inactive
The size distribution of most active sands is narrow and very fine (50‐150 micrometers) unless on a coarse‐grained (250‐500 micrometers size) ripple
Coarse‐grained ripples at Gale have similar grain sizes to those at both Gusev crater and Meridiani Planum landing sites
•We introduce the geologic mapping of Vesta Special Issue/Section of Icarus.•A geologic mapping campaign for Vesta was included as part of the Dawn Nominal Mission.•Geologic mapping of small airless ...bodies presents challenges not found on other planets.•We review the papers submitted for this Special Issue/Section.•We include a list of lessons learned from the mapping of Vesta, applicable to future missions.
The purpose of this paper is to introduce the Geologic Mapping of Vesta Special Issue/Section of Icarus, which includes several papers containing geologic maps of the surface of Vesta made to support data analysis conducted by the Dawn Science Team during the Vesta Encounter (July 2011–September 2012). In this paper we briefly discuss pre-Dawn knowledge of Vesta, provide the goals of our geologic mapping campaign, discuss the methodologies and materials used for geologic mapping, review the global geologic context of Vesta, discuss the challenges of mapping the geology of Vesta as a small airless body, and describe the content of the papers in this Special Issue/Section. We conclude with a discussion of lessons learned from our quadrangle-based mapping effort and provide recommendations for conducting mapping campaigns as part of planetary spacecraft nominal missions.
The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument onboard NASA’s
Perseverance
rover. SHERLOC combines imaging ...via two cameras with both Raman and fluorescence spectroscopy to investigate geological materials at the rover’s Jezero crater field site. SHERLOC requires
in situ
calibration to monitor the health and performance of the instrument. These calibration data are critically important to ensure the veracity of data interpretation, especially considering the extreme martian environmental conditions where the instrument operates. The SHERLOC Calibration Target (SCT) is located at the front of the rover and is exposed to the same atmospheric conditions as the instrument. The SCT includes 10 individual targets designed to meet all instrument calibration requirements. An additional calibration target is mounted inside the instrument’s dust cover. The targets include polymers, rock, synthetic material, and optical pattern targets. Their primary function is calibration of parameters within the SHERLOC instrument so that the data can be interpreted correctly. The SCT was also designed to take advantage of opportunities for supplemental science investigations and includes targets intended for public engagement. The exposure of materials to martian atmospheric conditions allows for opportunistic science on extravehicular suit (i.e., “spacesuit”) materials. These samples will be used in an extended study to produce direct measurements of the expected service lifetimes of these materials on the martian surface, thus helping NASA facilitate human exploration of the planet. Other targets include a martian meteorite and the first geocache target to reside on another planet, both of which increase the outreach and potential of the mission to foster interest in, and enthusiasm for, planetary exploration. During the first 200 sols (martian days) of operation on Mars, the SCT has been analyzed three times and has proven to be vital in the calibration of the instrument and in assisting the SHERLOC team with interpretation of
in situ
data.
Lacustrine sedimentary rocks of the Murray formation, Gale Crater, Mars, contain evidence for early diagenetic mineral precipitation. High‐resolution MAHLI images permit detailed morphological and ...spatial analysis of these features. Millimetre‐scale lenticular features occur in massive to well‐laminated mudstone and are interpreted as pseudomorphs after gypsum. The distribution and orientation of lenticular features indicate deposition at or near the sediment–water or sediment–air interface, and the lenticular form suggests crystallization in the presence of organic constituents. Original crystals were likely poikilotopic (i.e., incorporating elements of the matrix), and the original mineralogy was lost during later diagenetic fluid flow. Evidence for lenticular gypsum imaged in Gale Crater, along with earlier observations of potential early diagenetic evaporite precipitation made by the Opportunity rover, indicate that deposition of evaporitic sulfate minerals may have been widespread on early Mars.
We describe preliminary results from the first 100 sols of ground temperature measurements along the Mars Science Laboratory's traverse from Bradbury Landing to Rocknest in Gale. The ground ...temperature data show long‐term increases in mean temperature that are consistent with seasonal evolution. Deviations from expected temperature trends within the diurnal cycle are observed and may be attributed to rover and environmental effects. Fits to measured diurnal temperature amplitudes using a thermal model suggest that the observed surfaces have thermal inertias in the range of 265–375 J m−2 K−1 s−1/2, which are within the range of values determined from orbital measurements and are consistent with the inertias predicted from the observed particle sizes on the uppermost surface near the rover. Ground temperatures at Gale Crater appear to warm earlier and cool later than predicted by the model, suggesting that there are multiple unaccounted for physical conditions or processes in our models. Where the Mars Science Laboratory (MSL) descent engines removed a mobile layer of dust and fine sediments from over rockier material, the diurnal temperature profile is closer to that expected for a homogeneous surface, suggesting that the mobile materials on the uppermost surface may be partially responsible for the mismatch between observed temperatures and those predicted for materials having a single thermal inertia. Models of local stratigraphy also implicate thermophysical heterogeneity at the uppermost surface as a potential contributor to the observed diurnal temperature cycle.
Key Points
Diurnal ground temperatures vary with location
Diurnal temperature curves are not well matched by a homogeneous thermal model
GTS data are consistent with a varied stratigraphy and thermophysical properties
Sands at Gusev Crater, Mars Cabrol, Nathalie A.; Herkenhoff, Kenneth; Knoll, Andrew H. ...
Journal of geophysical research. Planets,
20/May , Volume:
119, Issue:
5
Journal Article
Peer reviewed
Open access
Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments ...for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine‐to‐medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).
Key Points
Textural analysis of the complete archive of the MER MI soil images
Distinct textural areas reflect the geographical divisions along the traverse
Processes, environments, and energy are inferred from particle shape and size
The morphology and composition of clasts have the potential to reveal the nature and extent of erosional processes acting in a region. Dense accumulations of granule‐ to pebble‐sized clasts covering ...the ground throughout the Glen Torridon region of Gale crater on Mars were studied using data acquired by the Mars Science Laboratory Curiosity rover between sols 2300 and 2593. In this study, measurements of shape, size, texture, and elemental abundance of unconsolidated granules and pebbles within northern Glen Torridon were compiled. Nine primary clast types were identified through stepwise hierarchical clustering, all of which are sedimentary and can be compositionally linked to local bedrock, suggesting relatively short transport distances. Several clast types display features associated with fragmentation along bedding planes and existing cracks in bedrock. These results indicate that Glen Torridon clasts are primarily the product of in‐situ physical weathering of local bedrock.
Plain Language Summary
Clasts are loose fragments produced by the breakdown of rock, which can be transported and reshaped by forces like water, wind and gravity. Clast shape, size, and texture are useful indicators of the clast's origin and the forces that have transported and modified it over time. The Glen Torridon region of Gale crater, the field site for the Mars Science Laboratory Curiosity rover, is covered at the surface by an abundance of granule‐ to pebble‐sized clasts. Between Martian days (“sols”) 2300 and 2593, Curiosity acquired images and compositional data of Glen Torridon clasts along the traverse. In this study, measurements of shape, size, texture, and composition of Glen Torridon granules and pebbles were compiled for characterization, and to determine their origin and erosional history. Nine primary clast types were identified, all of which are sedimentary rock and are similar in composition to the local bedrock, suggesting most clasts were transported short distances. Several clast types display features associated with fragmentation along bedding planes and existing cracks in bedrock. These results indicate that clasts in Glen Torridon are primarily the product of bedrock fragmentation.
Key Points
Clasts are abundant across the surface of Glen Torridon
Nine distinct clast types are identified throughout the region with different types representing distinct stages along the erosional continuum
Clasts are locally sourced and represent erosional and deflationary remnants of the Jura and Knockfarril Hill members
Abstract
We have constructed a global geologic map of the minor planet Vesta at 1:300,000-scale using Dawn spacecraft imaging, spectroscopic, topographic, and elemental data. In this effort, we used ...a mapping method that requires creating two maps independently: the first map uses morphology and topography to define map units, while the second map relies on multispectral data (“color”) to define units. The two are then combined into a hybrid product that retains the maximum amount of unique information from both maps in a readable format. This effort has revealed that for bodies where cratering is the dominant unit-forming process, and where there is not a close correlation between morphological feature types and multispectral signal, a hybrid mapping method better retains unique information carried by multispectral data during the mapping process than traditional morphology-based methods alone. Conversely, relying too heavily on color data risks placing too much emphasis on information drawn from the top few microns of the surface. To ensure both consistency and retention of unique information, we created a decision tree for determining which data would be primary in choosing where to draw unit boundaries. Also due to the significant amount of information borne by spectral data, we repurposed traditional mapping nomenclature so that subscripts carry color information. We recommend using this mapping methodology on bodies where (a) morphologic feature boundaries are commonly subtle, gradational, or both, and (b) spectral data carries a significant amount of unique data for identifying, characterizing, and interpreting geologic units.
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