Fragmented deoxyribonucleic acid could be extractable from Mars’s surface rocks

Detecting biomolecules in rocks is vital for understanding life’s evolution on Earth and its possible existence on Mars. The Curiosity rover measured Total Organic Carbon (TOC) levels of 201–273 ppm in 3500 million years (Ma)-old Martian mudstones exposed to radiation for 78 ± 30 Ma. Here we investigate whether deoxyribonucleic acid (DNA), a unique biological polymer, can be recovered under comparable conditions. We extracted and sequenced DNA from terrestrial sedimentary rocks with TOC ranging from 182 to 63,000 ppm, yielding 184,000 to 3.8 million nucleobases from a 0.5 g rock sample. After exposure to 10.45 MGy of gamma radiation, equivalent to 136 Ma on the Martian surface, we measured a radiolytic constant of K = 0.17 MGy⁻¹ in microbialite (2800-year-old) and oxide iron formation (2930 Ma old) samples. Despite fragmentation, 1.48–8.45% of sequences remained taxonomically identifiable, demonstrating that DNA fragments can persist in rocks for over 100 Ma. Taxonomically identifiable DNA can be recovered from terrestrial rocks containing as little as 182 ppm of total organic carbon after exposure to radiation equivalent to 136 million years on Mars, suggesting that biosignatures could remain detectable.