Biogenic calcium carbonate as evidence for life

A groundbreaking discovery reveals that moonmilk, a calcium carbonate deposit found in the Iron Age Etruscan necropolises of Cerveteri and Tarquinia, is of unequivocal biogenic origin. This makes it the only known carbonate speleothem on Earth with confirmed microbial involvement, serving as a robust biosignature of life. The study, conducted by Ronca et al., demonstrates that moonmilk precipitation is driven by endolytic bacterial communities within calcarenite and hybrid sandstone rocks, not just on their surfaces. This finding challenges traditional understanding of speleothem formation and underscores the significant role microbes play in rock evolution. The research employed a combination of microbial community analysis and geochemical investigations to elucidate this process.

Ronca, S., Mura, F., Brandano, M., Cirigliano, A., Benedetti, F., Grottoli, A., Reverberi, M., Maras, D. F., Negri, R., Di Mauro, E., & Rinaldi, T. (2023). Biogenic calcium carbonate as evidence for life. Biogeosciences, 20(19), 4135–4145. https://doi.org/10.5194/bg-20-4135-2023