Summary
Recent observation of Martian surface has yielded evidence of acidic, hypersaline, magnesium- and/or calcium-rich paleolakes that were intermittently available on ancient Mars. Because of their potential for habitability and preservation of bio-signatures in sediments deposited in a quiescent environment, paleolakes are considered high‐priority targets in the astrobiological exploration. These has provoked a rekindling of interest in study of similar geological formations that can be found on Earth, like calcium-saturated (6.0 M) surficial Don Juan Pond (DJP) (Wright Valley, Victoria Land, Antarctica). Tremendous salinity (> 470 g l-1) attributes this unfrozen shallow lake to the most harsh and polyextreme environment on Earth, where presence of liquid water is insufficient to support life. Indeed, up to date there are no conclusive evidences of microbes able to dwell in DJP brine and sediments. However, biological activity in form of microbial mats has been occasionally documented on the DJP waterside, where salinity/chaotropicity is reduced.

Objectives
Goal of our proposal is to understand to what extent life can withstand the multiple stresses occurring in this intriguing environment. This will be achieved by comprehensive study of both DJP brine/sediments and its shoreline, including modern molecular biology and bioinformatics, aw profiling, hydrochemistry and characterization of dissolved organic matter. We are confident that our findings will shed light on the plausibility of life in highly chaotropic environments, geochemical windows for microbial extremophiles, and will have implications for habitability studies elsewhere in the Solar System.

Project Partners
• National Institute of Oceanography and Experimental Geophysics (OGS)