P070-05
The Search for Fatty Acids on Mars: Results from the First In Situ Thermochemolysis Experiment at Gale Crater, Mars
Tuesday, 15 December 2020: 05:42
Virtual
Amy J Williams1, Jennifer L Eigenbrode2, Ross H Williams3, Arnaud Buch4, Samuel Teinturier2, Maëva Millan2,5, Daniel Patrick Glavin6, Caroline Freissinet7, Cyril Szopa8, Sarah Johnson5, Christine A Knudson9, James M. T. Lewis10, Amy McAdam11, Rafael Navarro-Gonzalez12, Roger E Summons13, Valerie K Fox14, Alexander B Bryk15, William B Brinckerhoff16, Charles Malespin2 and Paul R Mahaffy11, (1)University of Florida, Department of Geological Sciences, Ft Walton Beach, FL, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)Center for Research and Exploration in Space Science and Technology, University of Maryland, NASA Goddard Space Flight Center, Greenbelt, MD, United States, (4)CentraleSupelec, Gif-sur-Yvette, France, (5)Georgetown University, Washington, DC, United States, (6)NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, United States, (7)LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales, Paris Cedex 05, France, (8)Université Versailles St-Quentin, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales, Paris, France, (9)CRESST/University of Maryland College Park, College Park, MD, United States, (10)Center for Research and Exploration in Space Science and Technology, Howard University, Washington, DC, United States, (11)NASA Goddard SFC, Greenbelt, MD, United States, (12)Universidad Nacional Autonoma de Mexico, Mexico City, EM, Mexico, (13)Massachusetts Institute of Technology, Earth, Atmospheric and Planetary Sciences, Cambridge, MA, United States, (14)University of Minnesota, Earth and Environmental Sciences, Minneapolis, MN, United States, (15)University of California Berkeley, Earth and Planetary Science, Berkeley, CA, United States, (16)NASA, Greenbelt, MD, United States
Abstract:
The SAM instrument on the
Curiosity rover can perform wet chemistry experiments in conjunction with pyrolysis gas chromatography mass spectrometry (py-GC-MS) analysis of surface samples. Two cups in SAM contain reagents for thermochemolysis with tetramethylammonium hydroxide [TMAH] in 25% in methanol. These wet chemistry experiments transform polar organic molecules, such as carboxylic and amino acids, into volatile derivatives that are more amenable to GC-MS analysis, and free bound components of larger macromolecules otherwise undetectable with GC-MS. Of particular interest to astrobiology are carboxylic acids, bound in macromolecules or monomers bound to mineral phases, which could derive from abiotic or biotic sources. These are rendered detectable by transformation into methyl esters. The fatty acids (FA) used in terrestrial biology are abundant constituents of bacterial and eukaryotic cellular membranes, bound in phospholipids and glycolipids. These exhibit distinct even-over-odd carbon chain length preference due to their characteristic biosynthesis. Carboxylic acids are also found in carbonaceous meteorites, such as Murchison; however, these populations favor shorter carbon chain lengths and show no carbon number preference due to abiotic single-carbon-addition reactions. These patterns will aid in differentiating the sources of FA detected on Mars.
Specific SAM experiments in the Cumberland mudstone have yielded interesting results including the detection of C10 - C12 alkanes, which may originate from carboxylic acids. The first thermochemolysis experiment will occur in 2020 in Glen Torridon. Laboratory thermochemolysis of clay-rich analog samples have demonstrated that FA would be detectable if well preserved or recently present (<2 Ga). The SAM thermochemolysis experiment represents the first opportunity to detect organics bound in macromolecules on Mars. Beyond the science from Curiosity, the results and analytical features of this experiment on SAM will inform future missions. For example, a version of the TMAH thermochemolysis experiment is also featured in the Mars Organic Molecule Analyzer (MOMA) instrument onboard the 2022 ExoMars rover. The SAM results will critically underpin the corresponding MOMA analysis of clay-rich samples from depths up to two meters.
