NSS Convention 2026

Caves identified on Mars and the Moon highlight terrestrial caves as astrobiological analog environments. Biovermiculations—microbe-rich, dendritic rock coatings on cave walls—are a conspicuous potential biosignature. Most prior studies focus on sulfidic caves, linking their formation to sulfur cycling reactions [1][2]. Here, we investigate the biogeochemistry of biovermiculations in the carbonate karst system of Mammoth Cave (MC), Kentucky, USA, to compare with sulfidic systems and evaluate biogenicity. We hypothesize that MC biovermiculations form via a distinct microbiological mechanism involving active redistribution of surface material.

We integrate morphological classification, spatial mapping, live and epifluorescence microscopy, 16S rRNA gene sequencing, and metagenomics. MC biovermiculations occur in five morphological classes: simple, globule, intermediate, and complex A/B. Vermiculated material includes soot, fine-grained mud, and cricket guano. Spatial analyses indicate morphology correlates more strongly with material availability and substrate rheology than with proximity to other morphologies. Microscopy reveals motile microorganisms potentially capable of material redistribution. Growth extends into 19th–20th century candle soot but minimally alters post-1970s deposits, constraining formation timescales.

Preliminary genomic data indicate conserved microbial communities distinct from surrounding substrates. After Proteobacteria, Desulfobacterota is the second most abundant phylum, enriched ~10× relative to other locations. Beyond organic carbon oxidation, prevalent metabolic genes include sulfur and sulfite oxidation, iron and sulfate reduction, and methanotrophy. Ongoing DNA/RNA comparisons, isotopic (C/N) analyses, and cross-site comparisons will further resolve microbial contributions to material redistribution. Overall, this work develops a multiparameter framework for assessing biovermiculation biogenicity in cave systems.

[1] Hose, Palmer, Palmer, Northup, Boston & DuChene (2000), Chemical Geology 169:399–423.
[2] Jones, Lyon & Macalady (2008), Journal of Cave and Karst Studies 70:78-93.