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Catalytic Degradation of Organic Matter by Ferrous Iron-Rich Smectites on Mars: Replicating Sample Analysis at Mars (SAM) Pyrolysis Experiments in the Laboratory

Session: Advancing Mineral Science and Exploring Planetary Surfaces: In Honor of MSA Dana Medalist, Elizabeth B. Rampe (Posters)

Presenting Author:

Javi Estrada

Authors:

Estrada, Javi¹, Clark, Joanna Victoria², Malesky, Lauren³, Pamula, Krishnakumari⁴, Mitra, Kaushik⁵

(1) Department of Earth & Planetary Sciences, The University of Texas at San Antonio, San Antonio, TX, USA, (2) Amentum JETSII Contract at NASA Johnson Space Center, Texas State University, League City, TX, USA, (3) Department of Earth & Planetary Sciences, The University of Texas at San Antonio, San Antonio, TX, USA, (4) Department of Earth & Planetary Sciences, The University of Texas at San Antonio, San Antonio, TX, USA, (5) Department of Earth & Planetary Sciences, The University of Texas at San Antonio, San Antonio, TX, USA,

Abstract:

The preservation and detection of organic matter are important to astrobiological investigations and the search for preserved biosignatures on Mars. Carbonaceous chondrite meteorites have been proposed to be important sources of organic matter on the surface of Mars. High-temperature pyrolysis experiments by the SAM-Evolved Gas Analyzer (SAM-EGA) on the Curiosity rover have detected organic molecules in clay-rich Gale crater sediments. Both in-situ analyses and orbital remote sensing have detected phyllosilicates of dioctahedral (ferric or Fe(III)-rich) and trioctahedral (ferrous or Fe(II)-rich) varieties at multiple locations on Mars, including Gale crater. Clay minerals are proposed to be safe havens for organic matter on Mars . Phyllosilicate minerals have also been known for their catalytic effects on the maturation of complex organic matter or kerogen on Earth.

Kerogens are complex geological macromolecules of organic matter found in terrestrial sedimentary rocks. The presence of ‘matrix minerals’, such as iron oxides and clays, are known to catalyze the conversion of complex organic matter into simpler organic molecules during natural maturation during diagenesis. Additionally, matrix minerals have a catalytic effect on the thermal decomposition of organic molecules during laboratory thermal analysis. While the effect of iron oxides (e.g., hematite) and clay minerals (e.g., illite, kaolinite) have been investigated in previous studies, the influence of both di- and trioctahedral smectite minerals on organic matter degradation on Mars remains to be investigated. Here, we conduct laboratory SAM-Evolved Gas experiments to determine the impact of smectite clays on the thermal decomposition of organic matter under Mars-relevant conditions.

Utilizing a SAM analog system at NASA Johnson Space Center, we are investigating the impact of iron-rich phyllosilicate minerals, both Fe(II)/Mg smectites and Fe(III)-rich nontronites, on the thermal decomposition of simple as well as complex organic matter. While ferrous smectites are being synthesized in controlled anoxic environments in the laboratory, nontronite samples used in the analysis are mainly sourced naturally. A suite of organic molecules is being investigated: hopane [C₃₀H₅₂], polyethylene, naphthalene (C₁₀H₈), and kerogen type-III (coal samples). Mixtures of phyllosilicate minerals and organic matter substrates will be subjected to pyrolysis under Mars-like conditions, and products will be analyzed using standard analytical techniques.