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, 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.