Fatty Acid Preservation in Modern and Relict Hot-Spring Deposits in Iceland, with Implications for Organics Detection on Mars

Amy J Williams; Kathleen L Craft; Maëva Millan; Sarah Stewart Johnson; Christine A Knudson; Marisol Juarez Rivera; Amy C McAdam; Dominique Tobler; John Roma Skok

doi:10.1089/ast.2019.2115

Fatty Acid Preservation in Modern and Relict Hot-Spring Deposits in Iceland, with Implications for Organics Detection on Mars

Astrobiology. 2021 Jan;21(1):60-82. doi: 10.1089/ast.2019.2115. Epub 2020 Oct 29.

Authors

Amy J Williams^{1

2}, Kathleen L Craft³, Maëva Millan^{2

4}, Sarah Stewart Johnson^{4

5}, Christine A Knudson^{2

6}, Marisol Juarez Rivera⁷, Amy C McAdam², Dominique Tobler⁸, John Roma Skok⁹

Affiliations

¹ Department of Geological Sciences, University of Florida, Gainesville, Florida, USA.
² Planetary Environments Laboratory (Code 699), NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
³ Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA.
⁴ Department of Biology, Georgetown University, Washington, District of Columbia, USA.
⁵ Science, Technology, and International Affairs Program, Georgetown University, Washington, District of Columbia, USA.
⁶ CRESST Center for Research Exploration in Space Science and Technology at the University of Maryland, College Park, Maryland, USA.
⁷ School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA.
⁸ Department of Chemistry, Nano-Science Center, University of Copenhagen, Copenhagen, Denmark.
⁹ SETI Institute, Mountain View, California, USA.

PMID: 33121252
DOI: 10.1089/ast.2019.2115

Abstract

Hydrothermal spring deposits host unique microbial ecosystems and have the capacity to preserve microbial communities as biosignatures within siliceous sinter layers. This quality makes terrestrial hot springs appealing natural laboratories to study the preservation of both organic and morphologic biosignatures. The discovery of hydrothermal deposits on Mars has called attention to these hot springs as Mars-analog environments, driving forward the study of biosignature preservation in these settings to help prepare future missions targeting the recovery of biosignatures from martian hot-spring deposits. This study quantifies the fatty acid load in three Icelandic hot-spring deposits ranging from modern and inactive to relict. Samples were collected from both the surface and 2-18 cm in depth to approximate the drilling capabilities of current and upcoming Mars rovers. To determine the preservation potential of organics in siliceous sinter deposits, fatty acid analyses were performed with pyrolysis-gas chromatography-mass spectrometry (GC-MS) utilizing thermochemolysis with tetramethylammonium hydroxide (TMAH). This technique is available on both current and upcoming Mars rovers. Results reveal that fatty acids are often degraded in the subsurface relative to surface samples but are preserved and detectable with the TMAH pyrolysis-GC-MS method. Hot-spring mid-to-distal aprons are often the best texturally and geomorphically definable feature in older, degraded terrestrial sinter systems and are therefore most readily detectable on Mars from orbital images. These findings have implications for the detection of organics in martian hydrothermal systems as they suggest that organics might be detectable on Mars in relatively recent hot-spring deposits, but preservation likely deteriorates over geological timescales. Rovers with thermochemolysis pyrolysis-GC-MS instrumentation may be able to detect fatty acids in hot-spring deposits if the organics are relatively young; therefore, martian landing site and sample selection are of paramount importance in the search for organics on Mars.

Keywords: Fatty acids; Hot springs; SAM instrument.; Sinter; TMAH.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Ecosystem
Exobiology
Extraterrestrial Environment
Fatty Acids
Hot Springs*
Iceland
Mars*

Substances

Fatty Acids