Lakes on Early Mars: A Space-for-Time Substitution Experiment

Abstract:

Lakes were abundant and active on early Mars for 100s millions of years. As global climate change prevented liquid water from remaining stable at the surface, they left behind key evidence of their past existence and duration in the landscape morphology, mineralogy, composition, and topography. As significant markers of environmental change, they have become critical exploration targets for our understanding of Mars past habitability potential, and the preservation potential of their sediments make them high-priority candidate landing sites for the upcoming NASA and ESA rover missions that will search for evidence of biosignatures on early Mars.

Identifying and caching the most valuable samples with these missions will require to both recognize these signatures, the geological and environmental processes that may have modified them through time, the spatiotemporal constraints these processes could have imposed on a biogeological record, and their significance for biosignatures and their preservation potential.

To help us understand where, what, and how to search on Mars, the Chilean Atacama desert, Altiplano, and the High Andes have provided robust analog study sites over the past 20 years. Exposed to the strongest solar irradiance measured so far on our planet, from sea level up to 6,000 m elevation, and from glacial regions to some of the most arid conditions on Earth, these unique sites allow us to perform a space-for-time substitution experiments that shows the likely evolution of martian lake habitats over time from the early Noachian to the Hesperian. The observed changes provide critical clues about plausible scenarios for the evolution of habitability and life potential. They also give us pointers on how increased environmental extremes linked to a thinning unstable atmosphere, increasing UV, desiccation, and geological and climate changes, may have impacted biodiversity at local and global scale.