Biomarkers from Fossilised Hot Spring Sinters: Implications for the Search for Life on Mars

Abstract

Summary The search for life on Mars has been guided in part by the search for biosignatures in Martian analogues on Earth. Siliceous hot springs are key astrobiological targets as they provide ideal conditions for biogenesis. This work documents biomarker analyses carried out on siliceous hot spring sinters from El Tatio, Chile, and from the Taupo Volcanic Zone, New Zealand, with an age range from actively forming to fossil deposits (∼1–21 ka). In addition, older samples (Pliocene–Miocene) were analysed from the Coromandel Volcanic Zone, New Zealand. Some of the data have already been published. The key hydrocarbons detected in some (or all) of the samples include n-alkanes, isoprenoids, monomethylalkanes, tricyclic and tetracyclic terpanes, hopanes, 2α-methylhopanes, steranes, and some aromatic hydrocarbons. A series of biomarker and aromatic hydrocarbon maturity parameters suggest that most samples have entered the oil generation window, and that maturity is strongly variable between samples and by parameter. These signals are indicative of organic matter sourced from subsurface hydrothermal fluids migrating from deeper immature source rocks that have been hydrothermally altered, rather than from the in situ material preserved within the samples in the hot spring environment.