Preservation and Detection of Lipid Biosignatures in Modern Hot Spring Deposits using the Flight-like Experiments from the SAM and MOMA Instruments
Abstract
The search for traces of past life is a driving goal of the Mars exploration program. Terrestrial silica-rich rocks, such as the hot spring silica sinters actively forming in the Taupo Volcanic Zone (TVZ), New Zealand (NZ), have shown mineralogic and textural similarities with opaline silica deposits on Mars highlighted by the Spirit Mars Exploration Rover (e.g. Columbia Hills). Martian silica sinter could host and preserve lipid biomarkers and thus be relevant targets for the detection of organic biosignatures with Martian rovers, but silica sinters in general remain understudied and an especially good avenue for biosignature identification. Digitate spicular sinters were collected at six active geothermal fields in the TVZ around Rotorua in June 2018. They represent various physical and geochemical characteristics, including a range of fluid compositions (alkali-chloride, acid-sulfate chloride, acid sulfate and bicarbonate-sulfate), temperatures (from ambient to ~80°C) and pHs (1.6-8.4). The content and distribution of their lipid biosignatures were initially characterized in order to evaluate their preservation potential across conditions. Lipid biosignatures were detected in most of the environments regardless of water temperature or pH. Their organic geochemical distribution indicates the presence of plants and microbial lipids from active and/or recently active metabolisms. The samples are also currently being analyzed using flight-like analytical methods, akin to the Sample Analysis at Mars (SAM) instrument currently aboard the Curiosity rover and the MOMA (Mars Organic Molecular Analyzer) instrument that will be aboard the Exomars Rosalind Franklin rover. Techniques include flash-pyrolysis, SAM- and MOMA-like pyrolysis-GC-MS experiments, wet chemistry experiments (MTBSTFA, TMAH and DMF-DMA), and MOMA-like laser desorption (LD)-MS experiments. These ongoing investigations will improve our knowledge of the preservation of biosignatures in a range of hot spring Martian analog environments, and will illuminate the potential to detect lipids within siliceous spicules using flight-like experiments. These studies will also help us evaluate the possible limitations and biases induced by current and future flight-like experiments, enhancing biosignature detection strategies through laboratory experiment optimization, improve the understanding of the precursors and origin of the organic compounds detected on Mars, and add to our analog database for comparison with future analyses to be performed on Mars with next generation rovers.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1940M