In situ NanoSIMS geochemistry of an exceptionally well preserved Paleoarchaean carbonaceous microfossils – a key for planetary habitability

Analytical methods to distinguishing biotic from abiotic features are crucially important for search evidence of life that could include problematic and fragmentary organic remnants in ancient terrestrial rocks as well as in extra-terrestrial materials. The NanoSIMS is the only instrument that has the capability of measuring isotope ratios accurately from very small sample volumes. This project aims to establish by using the TA3-NanoSIMS the biogenicity of unique 3.41-3.33-billion-year-old microfilaments discovered in one of the oldest outcrops, which include the few known signs of early life. These microfilaments were found in a vein-infill hydrothermal system. The objectives are to obtain by NanoSIMS in situ measurements, the C-Si-O isotope ratios of these carbonaceous filaments and the associated clots and host Si-matrix. The C-isotope ratio would elucidate the biological nature of the filaments and possibly infer their metabolism, and would help in discerning if clots are abiotic or genuine fossil remains. The Si-O isotope ratio of the host Si-matrix would constrain the temperature of hydrothermal fluids and help in the paleoenvironmental reconstruction of a primordial life’s habitat. Hydrothermal systems are crucial targets in search for early life, and likely were the prevailing habitats of Earth at its beginning. A better knowledge of early terrestrial paleoenvironments could have important implications for elsewhere understanding the planetary evolution and habitability.