IMPACT GENERATED HYDROTHERMAL SYSTEMS: EARTH, MARS, AND BEYOND

Impact structures are the dominant geological features on rocky and icy bodies in the Solar System and impact cratering is the only ubiquitous geological process in the Solar System. Any hypervelocity impact into a water-rich target capable of generating a complex impact crater will result in impact induced hydrothermal activity. Mineralogical evidence of impact generated hydrothermal systems (IGHS) is preserved at ~70 of the ~183 terrestrial impact structures and spectrally determined mineral assemblages at several Martian impact craters are consistent with IGHS.

Impact-melted or -heated materials provide a transient exogenous heat source driving water circulation in an otherwise cold environment. The interaction of water with hot impactites forms a system of convective fluids that can dissolve, transport, and precipitate various mineral species. Following rapid, exponential cooling driven by steam production and degassing, a long period of gradual cooling can provide habitable conditions for thousands to millions of years. IGHS and associated mineral deposits are characterized by chemical and thermal disequilibria rendering them attractive systems for microbial colonization. The end of the Late Heavy Bombardment coincides with the earliest evidence of life on Earth leading to the speculation impact generated hydrothermal systems could have harboured early life on even played a role in the origin of life on Earth.

Impact-associated hydrothermal activity should have also been widespread on Mars, providing transient habitable conditions capable of circulating chemically active fluids for upwards of 10^5-7 years. With the availability of orbital high resolution spectral and imaging instrumentation capable of detecting hydrothermal phases such as clays and allowing for morphological and contextual integration, the detection of impact hydrothermal deposits around Martian craters is now becoming possible.