Canceled: DIX Planetary Science Seminar

This seminar is canceled. The next seminar is on 4/8/25.

Transient water-limited environments have historically hosted microbial communities early in Earth's history, and thus, may have been important ecosystems for life in ancient fluvial systems on Mars and water-limited environments on rocky Earth-like exoplanets. Similar environmental systems exist on Earth today, acting as meaningful analogs to study the preservation and detection of life in these environments. Particularly useful analogs are the McMurdo Dry Valleys of Antarctica, given their cold temperatures, aridity, elevated UV radiation exposure, and predominantly microbial ecosystem. Basins in these valleys contain ephemeral glacial meltwater streams, which contain a diversity of microbial communities only active when the streams are flowing ten weeks of the summer. These microbial communities were studied to examine how their in situ and remote biosignatures could inform the detection of similar life on Mars and rocky exoplanets.

In this talk, I will discuss how these organisms were found in association with carbonate rock coatings, morphologically resembling modern and ancient stromatolites from rivers, ponds, lakes, and hot springs. Microorganisms from these communities were found being preserved and influencing the formation of these coatings, becoming an additional Antarctic analog to ancient stromatolites. The presence of these carbonate coatings in an ephemeral stream suggests that processes in transient fluvial environments on Mars could have also generated coatings, which could have preserved biosignatures. I will also discuss how these microbial communities contained pigments, which were indicative of their community composition. The visible/near-infrared (VNIR) reflectance spectra of these communities were influenced by their pigments, demonstrating the capability of distinguishing microbial mat community composition using VNIR spectroscopy. Pigment absorption features acted as remote biosignatures that could then be applied to modeling the detection of similar life on the surfaces of cold and rocky Earth-like exoplanets. The detection times of Antarctic microbial mat remote biosignatures were compared with those of anoxygenic photosynthetic and nonphotosynthetic microorganisms, accounting for false positives, to determine which biosignatures were most detectable. The results from this work demonstrated the ability of the future space-based telescope, Habitable Worlds Observatory, to detect surface life on rocky Earth-like exoplanets.