ASTROBIOLOGICAL ANALOG STUDIES IN KARST SYSTEMS (Invited Presentation)

In order to better understand the potential for life elsewhere in the Solar System, it is important to understand the tenacity of life and the extreme limits where it can thrive. Life as we know it requires three dominant items for survival: (1) water, (2) carbon-based material, and (3) an energy source (direct or indirect). By studying life in environments where one (or more) of these needs are limited, comparisons can be drawn between extreme environs on Earth and the potential habitability of similar areas in the Solar System. For example, subterranean lakes of Earth present an opportunity to study isolated waters that are nutrient-limited as a potential analog to the waters of the icy moons of the Solar System.

With the anticipated launch of the Europa Clipper in 2024 to Europa, subterranean waters have become a subject of interest because of the potential comparisons between the nutrient-limited water and the interstitial lakes of the icy moons Europa and Enceladus. While many of these rare terrestrial waters require intensive boring to sample, caverns with subterranean lakes, such as Wind Cave in South Dakota provide direct access to subterranean water by human explorers.

These lakes contain an isolated, nutrient-limited biome that is an accessible terrestrial analog for low-biomass aqueous environments such as the oceans of Enceladus and Europa. Access to these lakes requires climbing and crawling ~3 km underground through passageways as small as 20 cm, limiting the amount of anthropogenic contamination from human visitors.

In contrast, river caves, such as Coldwater Cave in Iowa, flow with waters that are rich in surface runoff nutrients directing cave evolution along different directions.

In order to best determine how caves can serve as models of astrobiological nature, multiple aspects of the caves are under investigation including (1) tracing the flow of organics, (2) studying the microbial biodiversity of the caves, (3) tracing the anthropogenic microbial footprint through the caverns, and (4) laboratory analysis of cave waters to determine organic components.

These contrasting underground environments lend themselves to be used as analog sites for understanding the icy moons and for use as technique testbeds to enhance our exploration of the Solar System.