PICS Seminar: Alexandra Pontefract (MIT)
Understanding Habitability and Biosignature Preservation in Hypersaline Environments
The transition of Mars from wet to dry during the Hesperian (~3.7 Ga), resulted in widespread deposition of sulfate and some chloride salts that are observed on the surface today. Moreover, the discovery of polyhydrated sulfates on Mars, e.g., inside Columbus Crater in Terra Sirenum, has provided compelling evidence for the presence of paleolakes: some of which may represent remnants of evaporitic brine pools. On Earth, hypersaline lakes impose severe osmotic stress on microorganisms, including chaotrophic effects due to high levels of membrane destabilizing cations (Mg2+, Ca2+). Yet, these environments host an astonishing diversity of microorganisms and are capable of preserving evidence of life. For example, amino acids can be preserved for 4-40 Ma in salt crystals, and ATP (adenosine triphosphate) can remain “indefinitely” unhydrolyzed in hypersaline settings. If life existed on Mars, it is feasible that brine pools could have hosted a wide array of microorganisms, and under increasingly dehydrating conditions, salts may have provided a last refuge for surface or near-surface organisms. This talk will explore the constraints underpinning habitability in hypersaline environments, as well as the effects that salts have on biosignature preservation.
About the Series
The MIT Planetary Lunch Colloquium Series [PlCS] is a weekly seminar series organized within the EAPS department. Colloquia topics span the range of research interests of the department's planetary sciences research program. The seminars usually take place on Tuesdays from 12-1:30 pm in 54-517 unless otherwise noted (term-time only). Speakers include members of the MIT community and visitors. Talks are intended to appeal to graduate students, postdocs, research scientists, and faculty with a background in planetary science. A light lunch is provided.