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

This session honors MSA Dana Medalist Elizabeth B. Rampe, celebrating her contributions to Martian mineralogy and planetary science. We invite studies on in-situ and orbital planetary observations, lab/field data integration, and analog materials for extraterrestrial exploration.Sarah Simpson

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Manganese Phase and Oxidation State for Martian Analog Samples from Evolved Gas Analysis

Paper number: 153-8
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Manganese (Mn) enrichments have been identified by the APXS and ChemCam instruments onboard the Curiosity rover in fracture fills, coatings, and nodules at Gale crater, Mars. The enrichments can provide information about past geochemical conditions (e.g., oxidizing vs. reducing fluids) provided that the precise oxidation state and associated mineral phases of Mn are known or estimated. The goal of this study was to explore if analysis of martian samples by the Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA) can constrain the Mn-bearing phase and oxidation state.

Sixty-eight Mn-bearing samples (synthetic and natural) were analyzed using a thermal gravimetry (TG)/differential scanning calorimetry (DSC) instrument connected to a quadrupole mass spectrometer, configured to operate similarly to SAM (e.g., heating rate, furnace pressure, carrier gas). Results for evolved O2 Mn(II) oxides did not produce significant O2 peaks below 1000°C and therefore would not be detectable with SAM-EGA. Evolved O2 for higher valence Mn oxides (e.g., Mn2O3 and MnO2) took place between 460-1000°C and therefore would be detectable with SAM-EGA if present above SAM’s O2 detection limit of 0.01 wt. %. Laboratory EGA results for amorphous MnO and MnO2 were consistent with crystalline MnO and MnO2, respectively. This indicates that higher valence Mn oxides that are potentially in the X-ray amorphous component of drill samples could also be detectable by SAM-EGA.

Mn(II) carbonate, Mn(II) sulfate/sulfide, Mn(II) perchlorate, and Mn(II) oxalate are detectable by SAM-EGA as pure phases, showing characteristic CO2, SO2, HCl, and H2O, CO, and CO2 evolutions, respectively. In contrast, hydrated Mn phosphates would be difficult to discern with SAM-EGA because their water releases overlap with more abundant water-evolving phases such as hydrated salts or clays.

SAM-EGA could detect most but not all Mn-bearing phases if present above instrument detection limits. SAM-EGA is effective for detecting higher valence Mn oxides. Therefore, drill samples containing Mn oxides (detected by other rover instruments) that did not evolve O2 must be Mn(II) oxides or below detection. In oxidizing conditions Mn could precipitate into multiple phases detectible by SAM, and if detected would constrain Eh-pH to a greater degree than Fe alone.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414205

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