Fragmented DNA in rocks: Implications for the study of life on Mars and Earth

Detecting biomolecules in rocks is crucial for understanding the evolution of life on Earth and assessing its potential existence on Mars. The Curiosity rover has measured Total Organic Carbon (TOC) levels of 201–273 ppm in Martian mudstones exposed to radiation for 78 ± 30 million years. Here, we demonstrate that deoxyribonucleic acid (DNA) can be extracted and sequenced from terrestrial sedimentary rocks with TOC ranging from 182 to 63,000 ppm, yielding 184,000 to 3,800,000 nucleobases from a 0.5 g rock sample. After exposure to 10.45 MGy of radiation (equivalent to 136 million years on Mars) nucleobase degradation was quantified, with radiolytic constants of K = 0.17 +/- 0.09 MGy⁻¹ in microbialite (2800 years old) and oxide iron (2930 Ma old) samples. Despite significant fragmentation, 1.48–8.45% of sequences remained taxonomically identifiable. These findings suggest that rock matrices can protect DNA fragments for over 100 million years, preserving potential traces of past or present life on Mars.