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Elemental Relics: Biosignatures for Microbial Life in Terrestrial Hot Springs on Ancient Earth and Mars
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  • Andrew Gangidine,
  • Malcolm Walter,
  • Jeff Havig,
  • Andrew Czaja,
  • Daniel Sturmer,
  • Jeffrey Hannon
Andrew Gangidine
Cranbrook Institute of Science

Corresponding Author:[email protected]

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Malcolm Walter
University of New South Wales
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Jeff Havig
University of Minnesota
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Andrew Czaja
University of Cincinnati Main Campus
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Daniel Sturmer
University of Cincinnati Main Campus
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Jeffrey Hannon
University of Wisconsin Madison
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Terrestrial hot springs have existed throughout Earth’s history and house some of the most ancient evidence of life on our planet. These settings are known for their high habitability and preservation potential, and are extensively studied as analog environments since hot spring deposits are thought to exist on the surface of Mars. Hot spring water commonly precipitates silica that coats microbial life dwelling in the hot spring outflow streams. This process can entomb microorganisms and preserve microbial remains over long timescales and with high morphological fidelity. Here we present research carried out on modern and sub-recent remains of microbial filaments from amorphous (unaltered) silica deposits in Yellowstone National Park. This work suggests that various elements sequestered by hot spring-dwelling organisms during life are preserved in microbial remains and persist over > 10,000 years. We also present findings from microfossils preserved in mid-Paleozoic terrestrial hot spring deposits which also show sequestrations of select elements in microfossil remains, suggesting that certain elements may persist even after several hundred million years and substantial host rock alteration. These elemental concentrations may be indicative of metabolic functioning during life and have application as biosignatures. Recent developments in analytical instrumentation now allow for even extremely low trace elemental abundances to be detected and mapped, regardless of sample complexity. This work is especially relevant to the search for life on Mars, as evidence of impact-induced hydrothermal activity may exist near the rim of Jezero Crater and may be sampled by the Perseverance rover. As a primary objective of the Mars 2020 mission is to search for evidence of past life on Mars, we suggest the application of this analytical technique to be valuable for potential samples returned to Earth by future Mars Sample Return missions. Distribution Statement A. Approved for public release: distribution unlimited.