Geochemistry of Mineral-Water Interactions in Basaltic Lava Caves as
Earth Analogs (Screen 4)
Basaltic lava caves are important Earth analogs in our search for life
on Mars and other planets. Terrestrial lava caves exhibit
morphologically diverse secondary mineral deposits (speleothems) often
associated with liquid water. The detailed geochemical characterization
of cave water and speleothems can provide valuable insights on potential
biotic or abiotic mechanisms that lead to formation of these features.
Our results showed that the cave water chemistry is consistent with
basaltic host rock chemical composition. The water contained high levels
of dissolved organic carbon and nitrogen, which could support microbial
growth. The dissolved organic matter showed macromolecular structure and
appears to be plant-derived, highly humified and microbially processed.
Elevated nitrate in cave water may be due to agriculturally influenced
regional surface water source or in situ oxidation of ammonia or organic
N. Speleothems contained 29-79 wt% of crystalline, cryptocrystalline,
or amorphous SiO2, and secondary minerals containing biosignature
elements (Ca, Mg, Fe, Mn, S and V). This work complements the ongoing
NASA BRAILLE (Biologic and Resource Analog Investigations in Low Light
Environments) project to study basaltic lava tube caves as Earth analogs
and ultimately provide insights for planning future missions to search
for biosignature on Mars and other planetary bodies.