Rock Coatings as Evidence for Late Surface Alteration on the Floor of Jezero Crater, Mars

Abstract

During the NASA Perseverance rover's exploration of the Jezero crater floor, coatings were commonly observed on rocks. These features may record past water-rock-atmosphere interactions on the crater floor, and understanding their origin is important for constraining the timing of potential 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 alteration 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 the results from this study could provide important context for future investigations by the Mars Sample Return mission aimed at constraining the geologic and alteration history of Jezero crater.