Abstract
Detecting signs of potential extant/extinct life on Mars is challenging because the presence of organics on that planet is expected to be very low and most likely linked to radiation-protected refugia and/or preservative strategies (e.g., organo-mineral complexes). With scarcity of organics, accounting for biomineralization and potential relationships between biomarkers, mineralogy, and geochemistry is key in the search for extraterrestrial life. Here we explored microbial fingerprints and their associated mineralogy in Icelandic hydrothermal systems analog to Mars (i.e., high sulfur content, or amorphous silica), to identify potentially habitable locations on that planet. The mineralogical assemblage of four hydrothermal substrates (hot springs biofilms, mud pots, and steaming and inactive fumaroles) was analyzed concerning the distribution of biomarkers. Molecular and isotopic composition of lipids revealed quantitative and compositional differences apparently impacted by surface geothermal alteration and environmental factors. pH and water showed an influence (i.e., greatest biomass in circumneutral settings with highest supply and turnover of water), whereas temperature conditioned the mineralogy that supported specific microbial metabolisms related with sulfur. Raman spectra suggested the possible coexistence of abiotic and biomediated sources of minerals (i.e., sulfur or hematite). These findings may help to interpret future Raman or GC–MS signals in forthcoming Martian missions.
Highlights
Detecting signs of potential extant/extinct life on Mars is challenging because the presence of organics on that planet is expected to be very low and most likely linked to radiation-protected refugia and/ or preservative strategies
In the search for Martian life evidences, Jezero crater and Gusev crater are interesting targets due to the presence in both of amorphous silica, a mineral phase with high potential to preserve biosignatures on Earth that has been orbitaly identified in Jezero by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)[16] and in situ measured in Gusev by the Spirit r over[17]
We explored the molecular and isotopic composition of lipid biomarkers in four hydrothermal substrates
Summary
Detecting signs of potential extant/extinct life on Mars is challenging because the presence of organics on that planet is expected to be very low and most likely linked to radiation-protected refugia and/ or preservative strategies (e.g., organo-mineral complexes). We explored microbial fingerprints and their associated mineralogy in Icelandic hydrothermal systems analog to Mars (i.e., high sulfur content, or amorphous silica), to identify potentially habitable locations on that planet. Amongst the extreme terrestrial environments with a resemblance to Mars, geothermal hot springs and the associated sinter precipitates are well known habitable environments on the early Earth (e.g.,3,4 and references therein) that are considered potential analogs of hydrothermal processes on Mars (e.g.,5–7) These environments, including impact-generated hydrothermal s ystems[8,9], provide a localized source of heat, water, and the necessary materials to harbor life (e.g.,7,10). In the search for Martian life evidences, Jezero crater (landing site of the NASA’s Perseverance rover in 2021) and Gusev crater (landing site of the NASA’s Mars Exploration Rover Spirit in 2004) are interesting targets due to the presence in both of amorphous silica, a mineral phase with high potential to preserve biosignatures on Earth that has been orbitaly identified in Jezero by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)[16] and in situ measured in Gusev by the Spirit r over[17]
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