Hydrothermal activity generated by impact melt emplacement on the rim of Ritchey crater, Mars

Impact-induced hydrothermal systems have the potential to sustain long-lived aqueous environments throughout the history of Mars, yet their nature and distribution are not well-understood. While post-impact hydrothermal alteration on Mars has traditionally been studied at central peaks, we reported similar processes within a well-preserved impactite stratigraphy across the inner rim of Ritchey crater. This stratigraphy comprises a sheet unit overlying fragmented breccia, consistent with the emplacement of impact melt rocks on ballistic ejecta deposits, similar to features observed in complex craters on Earth. Analysis of CRISM hyperspectral data revealed alteration minerals including serpentine, chlorite, Mg-carbonate in fractured bedrock, veins, and erosional windows underneath the sheet unit. These alteration minerals are unrelated to post-impact fluvio-lacustrine facies or pre-impact target bedrock. Instead, their formation is most plausibly attributed to the emplacement of hot impact melt and subsequent groundwater percolation through fractured bedrock at the crater rim. The widespread distribution of the alteration minerals on the inner rim suggests that impact cratering can create extensive habitable environments. Our findings underscore the potential for alteration minerals at crater rims to preserve biosignatures, a key objective of the Mars 2020 mission at Jezero crater.