EPSS Colloquium winter-2019

Biosignatures are usefully thought of as anything observable that provides evidence of current or past life. Biosignature detection efforts focus on ancient Earth and planetary exploration. The Mars 2020 mission addresses key questions about the potential for life on Mars and aims to search for signs of past microbial life with the ultimate goal of caching samples for return to Earth. Should the Mars 2020 mission sample ancient rocks deposited by wind? We address this question by linking wind tunnel studies in simulated martian conditions and analog studies of modern, microbially influenced eolian environments at Padre Island, Texas. This talk presents results from wind tunnels experiments that determine a threshold for sporadic bursting. This threshold is lower than traditional continuous motion threshold models for Mars and lower than measured in situ wind speeds at Viking Lander 2 and Curiosity rover sites. This new threshold model paired with recent theory on sediment motion on Mars is consistent with orbital and in situ observations of active sand transport on Mars. The second part of the talk presents the role of thresholds in concentrating heavy minerals that are bound by microbial mats that occupy sabkhas in wet eolian systems; an explored environment on Mars. Upon burial, the heavy mineral horizons play a key role in identifying an eolian-environment biosignature. Handheld and imaging micro x-ray florescence (XRF) analysis of trench walls and sediment peels from trenches show distinctive textural and geochemical signatures linked to heavy minerals concentrated within the microbial mats at the surface.