We analyze Kodiak, an eroded delta remnant in Jezero Crater, Mars, using several hundred images from the Mastcam-Z and SuperCam instruments on the Mars 2020 Perseverance Rover. We create a high-accuracy digital terrain model to measure Kodiak’s stratigraphic layers, which we divide into three units and characterize individually. While each unit possesses geometries interpreted as consistent with a Gilbert-style delta formation, the older units exposed on Kodiak’s north to northeast sides include more complex layered structures with azimuthally varying foresets. We compare Kodiak’s northeast foresets with the clinoforms of Whale Mountain, an outcrop exposed in the Western Jezero Delta scarp, and show similar azimuthally varying foresets. The stratigraphic analysis presented herein (strike and dip, unit thickness, etc.) will help test and refine detailed sedimentological hypotheses for the formation and evolution of the Jezero delta. Our 3D reconstruction and measurements enable unprecedented precision to evaluate depositional models and advance geological interpretation.

During the NASA Perseverance rover’s exploration of the Jezero crater floor, purple-hued coatings were commonly observed on rocks. These features likely record past water-rock-atmosphere interactions on the crater floor, and understanding their origin is important for constraining timing of water activity and habitability at Jezero. Here we characterize the morphologic, chemical, and spectral properties of the crater floor rock coatings using color images, visible/near-infrared reflectance spectra, and chemical data from the Mastcam-Z and SuperCam instruments. We show that coatings are common and compositionally similar across the crater floor, and consistent with a mixture of dust, fine regolith, sulfates, and ferric oxides indurated as a result of one or more episodes of widespread surface alteration. All coatings exhibit a similar smooth homogenous surface with variable thickness, color, and spatial extent on rocks, likely reflecting variable oxidation and erosional expressions related to formation and/or exposure age. Coatings unconformably overlie eroded natural rock surfaces, suggesting relatively late deposition that may represent one of the last aqueous episodes on the Jezero crater floor. While more common at Jezero, these coatings may be consistent with rock coatings previously observed in-situ at other landing sites and may be related to duricrust formation, suggesting a global alteration process on Mars that is not unique to Jezero. The Perseverance rover likely sampled these rock coatings on the crater floor and results from this study could provide important context for future investigations by the Mars Sample Return mission aimed at constraining the geologic and aqueous history of Jezero crater.

Comets are active geological worlds with primitive surfaces that have been shaped to varying degrees by sublimation-driven sediment transport processes. Rosetta’s rendezvous with comet 67P/Churyumov-Gerasimenko (67P) in 2014 provided data with the necessary spatial and temporal resolutions to observe how micro-gravity worlds evolve. Rosetta’s observations have thus far revealed that the majority of changes to the surface occurred within 67P’s smooth terrains, vast sedimentary deposits that blanket a significant fraction of the nucleus. Understanding the global context of these changes, and therefore the sediment transport pathways that govern the evolution of 67P’s surface requires a thorough description of their changing morphologies, and an evaluation of existing global-scale spatial and temporal trends. Accordingly, we present a time-resolved synthesis of erosion and deposition activity on comet 67P as it passed through its August 13, 2015 perihelion from September, 2014 to August, 2016. Our mapping results indicate that, around perihelion, sediment is globally redistributed inter-regionally from 67P’s more active south to the north. Equally important, however, are local, topographically-influenced sediment transport processes, with large volumes of sediment moving intra-regionally over sub-kilometer scales. We also show evidence for regions of near-zero net erosion/deposition between approximately 30–60° latitude, which may act as terminal sedimentary sinks, with remobilization of these materials hindered by multiple factors. This work provides a complete mapping of the sediment transport processes and pathways across 67P observed by the Rosetta misison, and represents a critical step toward understanding the global landscape evolution of cometary surfaces.

The Mastcam-Z radiometric calibration targets mounted on the NASA’s Perseverance rover proved to be effective in the calibration of Mastcam-Z images to reflectance (I/F) over the first 350 sols on Mars. Mastcam-Z imaged the calibration targets regularly to perform reflectance calibration on multispectral image sets of targets on the Martian surface. For each calibration target image, mean radiance values were extracted for 41 distinct regions of the targets, including patches of color and grayscale materials. Eight strong permanent magnets, placed under the primary target, attracted magnetic dust and repelled it from central surfaces, allowing the extraction of radiance values from eight regions relatively clean from dust. These radiances were combined with reflectances obtained from laboratory measurements, a one-term linear fit model was applied, and the slopes of the fits were retrieved as estimates of the solar irradiance and used to convert Mastcam-Z images from radiance to reflectance. Derived irradiance time series are smoothly varying in line with expectations based on the changing Mars-Sun distance, being only perturbed by a few significant dust events. The deposition of dust on the calibration targets was largely concentrated on the magnets, ensuring a minimal influence of dust on the calibration process. The fraction of sunlight directly hitting the calibration targets was negatively correlated with the atmospheric optical depth, as expected. Further investigation will aim at explaining the origin of a small offset observed in the fit model employed for calibration, and the causes of a yellowing effect affecting one of the calibration targets materials.