Abstract
Impact-induced hydrothermal systems have the potential to support long-lived aqueous environments throughout the history of Mars, but their nature and distribution are not well-understood. We reported impact-induced alteration within a well-preserved impactite stratigraphy across the inner rim of Ritchey crater. The impactite stratigraphy is characterized by a smooth and uniform sheet unit overlying fragmented breccia, consistent with emplacement of impact melt rocks on ballistic ejecta deposits, as observed in the typical double layer impactites of complex craters on Earth. CRISM hyperspectral data revealed a series of alteration minerals including serpentine, chlorite, Mg carbonate in fractured bedrock, veins, and fragmented breccia in erosional windows underneath the unaltered sheet unit. These alteration minerals neither correlate with post-impact fluvio-lacustrine facies, nor with the pre-impact target bedrock. Instead, the formation of these alteration minerals is most plausibly triggered by the emplacement of hot impact melt, facilitating percolation of groundwater reacting with the extensively fractured and permeable bedrocks at the crater rims. The ubiquitous distribution of the alteration minerals on the inner rim indicates habitable environments triggered by impact cratering and potential preservation of biosignatures in the precipitated minerals.