121 Caves and Karst Through Space and Time: Biogeochemistry, Climate, and Astrobiology

We welcome submissions on the biogeochemistry, astrobiology, and historical records in of caves and karst features.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 211

Microbial Life Biosignatures in Earth's Extreme Lava Caves: Targets for Identifying Potential Extraterrestrial Life

Paper number: 121-3
Program: Technical Sessions
Time: 2:10 PM – 2:30 PM

Authors

Abstract

While the surface of Mars and other planetary bodies may seem unhabitable, scientists have suggested that the subsurface, particularly volcanic caves, is likely more habitable. Many lava caves worldwide contain a range of secondary mineral deposits in which we have documented communities of microorganisms that utilize elements within the deposits as energy sources, were engulfed as the deposits formed, or that helped precipitate the minerals in the deposits. These deposits and their microbial communities provide essential information for identifying best targets for searching for life on extraterrestrial bodies. Deposits of particular interest have been the mineral crusts, coralloids, polyps, fingers, spheroids, ooze, and moonmilk. Studying a range of these deposits in different locales allows us to identify the best mineral deposit morphologies for searching for life on Mars and other exoplanets and moons. Our research has explored this range of deposits in lava caves in Hawai`i Island, El Malpais National Monument (USA), the Azores, and Iceland, using DNA sequencing, scanning electron microscopy, and XRD. One of the Hawaiian caves studied was a newly formed lava cave, only four years old when we entered it. The different speleothems and microbial mats contained a variety of bacteria present including Bacillus, Nitrospira, Crossiella, and Euzebya, some of which are known to be key parts of the nitrogen cycle. Icelandic and Hawaiian lava caves have provided insights into the hidden microbial life and its remnants in a variety of mineral deposits. These observations can help us identify some of the best mineral/microbial deposits to investigate as we explore a variety of subsurface environments on exoplanets and moons.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412945

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