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Defining criteria for mapping material units on airless, rocky bodies is challenging. Where the primary geologic process for most of a body’s history is impact cratering, traditional morphology-based mapping approaches may fail, because differences in morphologic characteristics among the various cratered surfaces can be hard to discern, and surface morphology is muted by the regolith’s physical and mechanical properties. In constructing a global geologic map of Vesta at 1:300,000-scale using the Dawn Framing Camera (FC), DTM-derived slope and contour, and multispectral data, we have countered this problem by utilizing a hybrid method of mapping that first requires creating two maps independently. The first map depends on morphology and topography to define map units, while the second uses spectral data to define units. The unique results of each map are then combined into the hybrid map units. Multispectral data provide unique insight into stratigraphy (material brought up through cratering processes) that is easily lost when using an albedo mosaic as the basemap. However, solely using a “color” ratio mosaic as a basemap easily magnifies potentially misleading data, because spectroscopy in the shorter wavelengths (UV-VIS-near IR) can only sample the upper few µm of the surface, and very little unique material is required to affect the signal of a regolith. Contacts defined by multispectral data may not coincide with clear morphologic boundaries as a result, so caution must be used in how the two maps are merged and clear criteria should be established to define hybrid map units. We found that the crucial exercise in ensuring unique data were retained when combining these two maps was to create a decision tree for determining which data would be primary in choosing where to draw unit boundaries. We divided the decision tree into the following if-then statements:If saturated colors (meaning the color signal in color-ratio spectral data was strong and the color itself was easy to describe) matched unit boundaries derived from morphology, there was no conflict. For example, saturated colors on Vesta tend to be associated with fresher expressions or exposures of regolith, which are more likely found at the youngest, freshest craters/ejecta, easily demarcated morphologically. If muted colors exist, where the morphology is relatively clear, the morphology is the primary guide for unit definition, as it retains the least altered record of geologic processes and the most reliable record of the nature of the rock bodies. Colors provide additional characteristics of such units, allowing for some interpretation of composition. If saturated colors are not associated with morphologic boundaries, the color boundaries are interpreted to record the most recent (even if very thin) impact evidence. In such cases we have mapped the saturated color data as impact material. This preserves the underlying morphology/topography information while supporting stratigraphic interpretations based on excavated subsurface layers revealed by crater ejecta. In the case of muted colors where the morphology is unclear, decisions must be made case-by-case, using all available data to make a reasonable determination of where to mark unit boundaries.

Covering the time between Curiosity’s 3424th and 3547th Martian days (sols) of operations in northern Gale crater, Mars, this document is a compilation of the Mars Science Laboratory (MSL) Mars Hand Lens Imager (MAHLI) Team’s notes and information about MAHLI images and activities conducted during that period. The report includes brief sol-by-sol notes—written as the mission unfolded—regarding how the MAHLI instrument was used and significant events that occurred which impacted the MAHLI instrument or investigation. The document, further, contains information regarding range and scale (camera working distance and scale of in-focus elements of an image); the parent images, range, and scale information associated with each MAHLI focus merge product created onboard the instrument; and a description of the purpose and intent behind acquisition of each MAHLI image and creation of each onboard focus merge product. The MSL science team and rover engineers routinely used the information contained in this report during the course of the mission for tactical planning, strategic planning, and scientific analysis.

International audience; The “Marker Band” (previously called the Marker Bed and Marker Horizon [1-4]) in Gale crater is a distinctive indurated and dark-toned unit observed in the strata of Mount Sharp. From orbital data, the Marker Band (MB) was mapped across much of the western and southern edges of Mount Sharp, spanning over 80 km in distance and 1.6 km in elevation [4]. CRISM spectra of the MB show no hydration signatures and broad absorptions around~1 and 2 μm interpreted to be from high-Ca pyroxene [4]. Favored origins for the MB based upon orbital observations included a more indurated sulfate, a sandstone, and a volcanic ash deposit. The Curiosity rover recently reached the MB and is now collecting critical in situ measurements to test these postulated and other origins and make new discoveries at the finer mm- to cm-scale that could not be assessed from orbital data. Here we provide a summary of several of the most crucial MB observations made by the rover thus far from sols 3640-3645 and 3668-present.

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 S & eacute;& iacute;tah 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 M & aacute;az and S & eacute;& iacute;tah 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.Plain Language Summary We used multiple instruments on the Perseverance rover to describe three populations of loose sediments found on the floor of Jezero crater by their grain sizes and chemical compositions. The smallest population has grains that are small sand-sized (80-530 mu m) and a mixture of minerals commonly found on Mars, including pyroxene that is present in local rocks and airborne dust found globally. These grains are the easiest to move by wind, so could have distal regional sources as well. Larger gray grains that are 1-2 mm in size and rounded contain olivine. These grains move along the surface, pushed by the impacts of smaller grains that are lifted by the wind. Their size and composition are very similar to olivine grains found in nearby in-place rocks, indicating that they may have a more local source. Finally, there are larger pieces of rocks that have broken down from the erosion of local in-place rocks over time and mix with the other types of grains. Loose sediments within the Jezero crater described here can be compared to loose sediments studied at other landing sites on Mars to help understand how Jezero sediments are formed and transported.

Covering the time between Curiosity’s 3290th and 3423rd Martian days (sols) of operations in northern Gale crater, Mars, this document is a compilation of the Mars Science Laboratory (MSL) Mars Hand Lens Imager (MAHLI) Team’s notes and information about MAHLI images and activities conducted during that period. The report includes brief sol-by-sol notes—written as the mission unfolded—regarding how the MAHLI instrument was used and significant events that occurred which impacted the MAHLI instrument or investigation. The document, further, contains information regarding range and scale (camera working distance and scale of in-focus elements of an image); the parent images, range, and scale information associated with each MAHLI focus merge product created onboard the instrument; and a description of the purpose and intent behind acquisition of each MAHLI image and creation of each onboard focus merge product. The MSL science team and rover engineers routinely used the information contained in this report during the course of the mission for tactical planning, strategic planning, and scientific analysis.

The stratigraphy preserved within Aeolis Mons (Mount Sharp) in Gale crater (Mars) shows a major transition from mudstone-rich strata (with subordinate sandstones) recording deposition in lacustrine to fluvial settings into a major sulphate-bearing unit (the Layered Sulphate-bearing unit (LSu)) [1, 2]. This transition is interpreted to represent a major environmental change from wetter conditions toward a more arid palaeoclimate on early Mars. A stratigraphic section over this transition constructed along Curiosity’s traverse shows a vertical change from mudstones with interstratified sandstones of the Glasgow and Mercou members of the Carolyn Shoemaker formation into strata of the Pontours member which have a strong diagenetic overprint, and thence into large-scale cross-stratified sandstones of the Mirador formation that are interpreted to be the deposits of large, migrating aeolian dunes. The lower section of the LSu is dominated by stacked, cross-bedded facies with variable diagenetic overprint, that likely records a purely dry aeolian dune environment [3]. However, higher up in the studied section, approximately 80 m above the base of the Mirador formation, there is a transition into a succession still dominated by large-scale cross-beds but with interstratified lenses of a different sandstone facies. The presence of these lenses within large-scale cross bedded rocks is denoted by a transition to the Contigo member of the Mirador formation. Whilst a number of lenses are visible in the stratigraphy of the Contigo member in cliffs along Curiosity’s traverse, the Mars Science Laboratory science team selected one lens, informally named The Prow to investigate in detail. Here, we describe the sedimentology of The Prow at a range of scales using Navcam, Mastcam, ChemCam Remote Micro-Imager(RMI), and Mars Hand Lens Imager (MAHLI) images with a focus on characterizing sedimentary structures, their depositional process interpretation and comparison to Earth analogs. The 3D geometries of The Prow’s sedimentary structures are analysed by [4]. The Prow was investigated during sols 3349 and 3379 in early 2022 and had been identified as a target of interest from long distance observations suggesting that it formed constrasting facies to surrounding rocks. The Prow is an ~18-m-long, ~0.5-1-m-thick lenticular sedimentary body that is interbedded with large-scale cross-stratified facies interpreted to be aeolian dune deposits. The nature of the lower contact of The Prow is unclear. The lens pinches out to the south. The Prow shows a range of sedimentary structures suggestive of deposition under predominantly aqueous conditions. These structures differ from structures in surrounding bedrock indicating contrasting environmental conditions. The lowermost part of The Prow section appears to comprise decimetre-scale cross-beds indicative of deposition from subaqueous dune migration. The scale of these cross-beds is quite different from the large metres-scale trough cross-beds in rocks surrounding the lenses. The upper sections of The Prow are dominated by cm-scale ripple structures well observed in cross-section. In particular, lenticular and flaser geometries are observed. Lenticular ripple forms with convex upper surfaces are common with concave lower surfaces where they overlie underlying ripple forms. The ripple forms occur vertically stacked and laterally offset. The individual lenses are commonly interconnected forming complex interwoven structures. The crests generally show rounded symmetric profiles. Locally, symmetric vertical accretion over ripple crests is observed implying rapid sediment aggradation. Many ripple forms do not appear to show internal lamination, although this may be due to a lack of grain size variation. In a few examples where internal lamination is observed, preserved foresets are suggestive of unidirectional flow. RMI and MAHLI images reveal that ripple forms appear to have a finer-grained drape overlying ripple crests and extending into ripple troughs. MAHLI data confirm initial ChemCam observations and show that ripple cores comprise a sandstone and draping laminations are finer grained and likely below MAHLI-resolution (~60 microns). The drapes are provisionally interpreted as mud drapes formed from suspension fallout onto ripple topography during low energy quiescent episodes. The overall sedimentary geometry resembles flaser- to lenticular bedding common in Earth examples. The symmetric form of many of the ripple structures with preservation of form sets is suggestive of formation by oscillatory flow by wave action. Locally, there is evidence of asymmetric accretion which is likely indicative of combined flow ripples. The presence of drapes of finer-grained material superimposed on coarser-grained ripple forms is interpreted to record episodes of higher-energy sand transport separated by recurrent intervals of low-energy conditions during which sand grains could not be mobilised. Wave and current activity caused bedload transport of sand constructing symmetric and asymmetric ripples. Between these episodes, there were quiescent periods where active flow ceased and finer-than-sand grains deposited out of suspension onto temporarily fossilised ripple forms. The preservation of stacked well-preserved ripple forms with crests intact suggests conditions of rapid deposition. Locally, planar laminated beds with laterally continuous laminae are present; these maybe interpreted as either wind-ripple laminations formed by aeolian transport or as upper flow regime plane beds. The presence of mudstone-draped wave and current ripple forms in the upper section of The Prow is strongly indicative of deposition from aqueous flows and moreover suggests the existence of a likely aerially small, shallow standing body of water in which the sediments were deposited. We compare the observed structures to forms observed in 1 Ga lake deposits from the Diabaig Formation of the Torridon Group (NW Scotland). We tentatively infer that The Prow and by inference the other lenses observed in the Contigo member may record the episodic interdune or scour-fill presence of transient small standing bodies of water in an otherwise dominantly dry aeolian dune-dominated environment. The vertical transition from the underlying Dunnidear and Port Logan members of the Mirador formation that are dominated purely by large-scale trough cross bedding indicative of dry aeolian conditions indicates a change to a more mixed environmental setting with episodic fluvial/lacustrine activity perhaps from transient snow-melt or precipitation events occurring in otherwise arid conditions. Lenses such as The Prow demonstrate fluvio-lacustrine intervals punctuated dominant aeolian environment in the layered sulphate-bearing unit. References: [1] Milliken et al., 2010, Geophys. Res. Lett. 37, L04201; [2] Rapin et al., 2021, Geology 49; [3] Rapin et al., 2022, EPSC, this meeting; [4] Caravaca et al., 2022, EPSC, this meeting.

At a Mars analog site in Utah, we tested two science operation methods for data acquisition and decision-making protocols: a scenario where the tactical day is preplanned, but major adjustments may still be made before plan delivery; and a scenario in which the sol path must largely be planned before a given tactical planning day and very few adjustments to the plan may be made. The goal was to provide field-tested insight into operations planning for rover missions where science operations must facilitate the efficient choice of sampling locations at a site relevant to searching for habitability and biosignatures. Results of the test indicate that preplanning sol paths did not result in a sol cost savings nor did it improve science return or optimal biologically relevant sample collection. In addition because facies variations in an environment can be subtle and evident only at scales below orbital resolution, acquiring systematic observations is crucial. We also noted that while spectral data provided insight into the chemical components as a whole at this site, they did not provide a guide to targets for which the traverse should be altered. Finally, strategic science planning must include a special effort to account for terrain.

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.

Covering the time between Curiosity’s3193rd and 3289th Martian days (sols) of operations in northern Gale crater,Mars, this document is a compilation of the Mars Science Laboratory (MSL) MarsHandLens Imager (MAHLI) Principal Investigator’s notes and information aboutMAHLI images and activities conducted during that period. The report includes briefsol-by-sol notes—written as the missionunfolded—regarding how the MAHLIinstrument was used and significant events that occurred which impacted theMAHLI instrument or investigation. The document, further, contains informationregarding range and scale (camera working distance and scale of in-focuselements of an image); the parent images, range, and scale informationassociated with each MAHLI focus merge productcreated onboard the instrument;and a description of the purpose and intent behind acquisition of each MAHLIimage and creation of each onboard focus merge product. The MSL science teamand roverengineers routinely used the information contained in this reportduring the course of the mission for tactical planning, strategic planning, andscientific analysis.

We conducted a field test at a potential Mars analog site to provide insight into planning for future robotic missions such as Mars 2020, where science operations must facilitate efficient choice of biologically relevant sampling locations. We compared two data acquisition and decision-making protocols currently used by Mars Science Laboratory: (1) a linear approach, where sites are examined as they are encountered and (2) a walkabout approach, in which the field site is first examined with remote rover instruments to gain an understanding of regional context followed by deployment of time- and power-intensive contact and sampling instruments on a smaller subset of locations. The walkabout method was advantageous in terms of both the time required to execute and a greater confidence in results and interpretations, leading to enhanced ability to tailor follow-on observations to better address key science and sampling goals. This advantage is directly linked to the walkabout method's ability to provide broad geological context earlier in the science analysis process. For Mars 2020, and specifically for small regions to be explored (e.g.

Covering the time between Curiosity’s3069th and 3192nd Martian days (sols) of operations in northern Gale crater,Mars, thisdocument is a compilation of the Mars Science Laboratory (MSL) MarsHand Lens Imager (MAHLI) Principal Investigator’s notesand information aboutMAHLI images and activities conducted during that period. The report includes briefsol-by-sol notes—written as the mission unfolded—regarding how the MAHLIinstrument was used and significant events that occurred whichimpacted theMAHLI instrument or investigation. The document, further, contains informationregarding range and scale (cameraworking distance and scale of in-focuselements of an image); the parent images, range, and scale informationassociated witheach MAHLI focus merge product created onboard the instrument;and a description of the purpose and intent behind acquisitionof each MAHLIimage and creation of each onboard focus merge product. The MSL science teamand rover engineers routinelyused the information contained in this reportduring the course of the mission for tactical planning, strategic planning, andscientific analysis.

Granule- to cobble- sized clasts in the Glen Torridon region of Gale crater on Mars were studied using data captured by NASA’s Mars Science Laboratory Curiosity rover between sols 2302 and 2593. Th...

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.

The Mars Science Laboratory Curiosity rover conducted a reconnaissance traverse across the Pahrump Hills outcrop within Gale crater from Sols 780–797. During the traverse, the Mars Descent Imager (MARDI) acquired a continuous imaging record of primary and secondary sedimentary features throughout the outcrop. The characteristics of the features (laminae, resistant features, fractures, gray clasts) and their spatial distribution provide insight into the processes that contributed to the formation of Pahrump Hills. Thin, regular laminae (mm-scale) are ubiquitous in the bedrock, implying that depositional processes at that scale did not change appreciably during deposition of the mudstone succession at Pahrump Hills. Higher bedrock slopes correlate with undulatory bedrock surfaces, bedrock with elevated Mg contents, and fractures exhibiting wide, raised edges. These collective features are consistent with increased erosional resistance caused by greater quantities of erosionally-resistant, Mg-bearing cement within the bedrock permitted by coarser grain sizes. Resistant features exhibit a range of morphologies, elevated Mg contents, and do not deflect laminae within the bedrock. Their characteristics implicate the involvement of Mg-enriched fluids in a late diagenetic overprint affecting the bedrock. The variations of fracture fill and edge morphologies and chemistries further suggest repeated fracturing and fluid interaction events within the strata exposed at Pahrump Hills. Gray clasts strongly resemble fragments eroded from sandstone horizons interspersed throughout the Pahrump Hills outcrop.

The Desert RATS field analogue tests in 2010 and 2011 utilized the position of Science Communicator (SciCom) as that of a communications facilitator among the test's astronaut crews, science backrooms, and flight operations team. Based on the traditional role of the Spacecraft Communicator (CapCom), the SciCom was tasked with utilizing their science expertise to understand the inputs from the science backroom, and to quickly and effectively distill those into executable tasks communicated to the crew. The role was demonstrated to be a crucial component of the success of these tests. Certain skills were determined to be essential for a SciCom to develop; these included science knowledge germane to the mission, good communications skills, diplomacy, the ability to multitask, and the ability to advocate for the crew. Key attributes of the SciCom role include: the ability to balance science team goals and requirements with crew needs on a science-driven tactical timeline; using good judgment, strong situational awareness, foresight, and experience to meet the needs of each team; fostering a good relationship with their Science Lead (SciLead); anticipating and being proactive in addressing issues; and strengthening constructive cross-referencing and cross-education with the SciLead. These attributes mimic the relationship between the CapCom and the Flight Director.

Recent robotic missions to Mars have offered new insights into the extent, diversity and habitability of the Martian sedimentary rock record. Since the Curiosity rover landed in Gale crater in August 2012, the Mars Science Laboratory Science Team has explored the origins and habitability of ancient fluvial, deltaic, lacustrine and aeolian deposits preserved within the crater. This study describes the sedimentology of a ca 13 m thick succession named the Pahrump Hills member of the Murray formation, the first thick fine‐grained deposit discovered in situ on Mars. This work evaluates the depositional processes responsible for its formation and reconstructs its palaeoenvironmental setting. The Pahrump Hills succession can be sub‐divided into four distinct sedimentary facies: (i) thinly laminated mudstone; (ii) low‐angle cross‐stratified mudstone; (iii) cross‐stratified sandstone; and (iv) thickly laminated mudstone–sandstone. The very fine grain size of the mudstone facies and abundant millimetre‐scale and sub‐millimetre‐scale laminations exhibiting quasi‐uniform thickness throughout the Pahrump Hills succession are most consistent with lacustrine deposition. Low‐angle geometric discordances in the mudstone facies are interpreted as ‘scour and drape’ structures and suggest the action of currents, such as those associated with hyperpycnal river‐generated plumes plunging into a lake. Observation of an overall upward coarsening in grain size and thickening of laminae throughout the Pahrump Hills succession is consistent with deposition from basinward progradation of a fluvial‐deltaic system derived from the northern crater rim into the Gale crater lake. Palaeohydraulic modelling constrains the salinity of the ancient lake in Gale crater: assuming river sediment concentrations typical of floods on Earth, plunging river plumes and sedimentary structures like those observed at Pahrump Hills would have required lake densities near freshwater to form. The depositional model for the Pahrump Hills member presented here implies the presence of an ancient sustained, habitable freshwater lake in Gale crater for at least ca 10^3 to 10^7 Earth years.

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.

We conducted geologic mapping of the Urvara (Ac-13) and Yalode (Ac-14) Quadrangles (21–66°S, 180–360°E) of the dwarf planet Ceres utilizing morphologic, topographic, and compositional information acquired by NASA's Dawn mission. The geologic characteristics of the two large impact basins Urvara (170 km diameter) and Yalode (260 km diameter) and their surroundings were investigated using Dawn Framing Camera datasets, including Survey (415 m/pixel), HAMO (140 m/pixel), and LAMO (35 m/pixel) images and mosaics, color and color ratio images, and DTMs derived from stereo-photogrammetry. Geologic mapping demonstrates that impact cratering has dominated the geologic history of the Urvara and Yalode Quadrangles, with early cratered terrain formation followed by formation of the large basins and widespread emplacement of basin-related smooth material. Impact craters display a wide range of preservation states from nearly completely buried/degraded forms to more recent pristine craters with terraced inner walls and lobate ejecta deposits. Cross-cutting relationships and morphologic signatures show that the Urvara impact followed the Yalode impact, consistent with ages derived from crater size-frequency distributions (580 ± 40 Ma for Yalode and 550 ± 50 Ma for Urvara). Observed differences in basin materials and rim morphology suggest heterogeneities in the substrate excavated by impact. Smooth deposits that cover large areas of the quadrangles, including the basin floors, rims, and exterior zones, are interpreted to be dominated by Urvara ejecta but Yalode ejecta and localized ice-rich flow material may be minor components. Geologic mapping results and simulations of ejecta emplacement suggest that Urvara and Yalode ejecta deposits extend for large distances (more than two crater diameters from the basin centers) and may serve as important stratigraphic markers for the geologic record of Ceres.

Geochronology, or determination of absolute ages for geologic events, underpins many inquiries into the formation and evolution of planets and our Solar System. Absolute ages of ancient and recent magmatic products provide strong constraints on the dynamics of magma oceans and crustal formation, as well as the longevity and evolution of interior heat engines and distinct mantle/crustal source regions. Absolute dating also relates habitability markers to the timescale of evolution of life on Earth. However, the number of geochronologically-significant terrains across the inner Solar System far exceeds our ability to conduct sample return from all of them. In preparation for the upcoming Decadal Survey, our team formulated a set of medium-class (New Frontiers) mission concepts to three different locations (the Moon, Mars, and Vesta) where sites that record Solar System bombardment, magmatism, and/or habitability are uniquely preserved and accessible. We developed a notional payload to directly date planetary surfaces, consisting of two instruments capable of measuring radiometric ages in situ, an imaging spectrometer, optical cameras to provide site geologic context and sample characterization, a trace element analyzer to augment sample contextualization, and a sample acquisition and handling system. Landers carrying this payload to the Moon, Mars, and Vesta would likely fit into the New Frontiers cost cap in our study (~$1B). A mission of this type would provide crucial constraints on planetary history while also enabling a broad suite of investigations such as basic geologic characterization, geomorphologic analysis, ground truth for remote sensing analyses, analyses of major, minor, trace, and volatile elements, atmospheric and other long-lived monitoring, organic molecule analyses, and soil and geotechnical properties., Comment: Submitted to the Planetary Science Journal, October 2020

Stack, K. et al., The Mars 2020 Perseverance rover landing site is located within Jezero crater, a ∼50km 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., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

Extraformational sediment recycling (old sedimentary rock to new sedimentary rock) is a fundamental aspect of Earth's geological record; tectonism exposes sedimentary rock, whereupon it is weathered and eroded to form new sediment that later becomes lithified. On Mars, tectonism has been minor, but two decades of orbiter instrument-based studies show that some sedimentary rocks previously buried to depths of kilometers have been exposed, by erosion, at the surface. Four locations in Gale crater, explored using the National Aeronautics and Space Administration's Curiosity rover, exhibit sedimentary lithoclasts in sedimentary rock: At Marias Pass, they are mudstone fragments in sandstone derived from strata below an erosional unconformity; at Bimbe, they are pebble-sized sandstone and, possibly, laminated, intraclast-bearing, chemical (calcium sulfate) sediment fragments in conglomerates; at Cooperstown, they are pebble-sized fragments of sandstone within coarse sandstone; at Dingo Gap, they are cobble-sized, stratified sandstone fragments in conglomerate derived from an immediately underlying sandstone. Mars orbiter images show lithified sediment fans at the termini of canyons that incise sedimentary rock in Gale crater; these, too, consist of recycled, extraformational sediment. The recycled sediments in Gale crater are compositionally immature, indicating the dominance of physical weathering processes during the second known cycle. The observations at Marias Pass indicate that sediment eroded and removed from craters such as Gale crater during the Martian Hesperian Period could have been recycled to form new rock elsewhere. Our results permit prediction that lithified deltaic sediments at the Perseverance (landing in 2021) and Rosalind Franklin (landing in 2023) rover field sites could contain extraformational recycled sediment., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)