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

Comparative Study of Manganese Oxidation in Martian Fluids: Oxygen v. Oxyhalogens v. Nitrate.

Paper number: 153-7
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Oxidized manganese [Mn(III/IV)] deposits discovered in veins and fractures are key indicators of past redox conditions and potential habitability on Mars. On Earth, manganese oxidation is primarily driven by molecular oxygen (O2) in alkaline conditions or catalyzed by microbial activity, processes that became abundant during the Great Oxidation Event (~2.3 Ga). However, ancient Mars lacked a substantial O2 atmosphere, with estimated concentrations ranging from 0.05 to 10-5 bar, making the mechanism of Martian manganese oxidation a subject of debate. While some previous experimental data on Mn(II) oxidation by O2 or simple oxyhalogen systems exist, the accurate determination of the rate and products of such oxidation in Mars-relevant conditions, specifically by O2 in hydrothermal closed and open systems, mixed chlorate-bromate anions, and nitrate, remains underexplored. This study experimentally investigates oxygen (O2), mixed oxyhalogens (chlorate and bromate), and nitrate (NO3-) to determine the most effective and plausible oxidant responsible for manganese oxidation on Mars in Mars-relevant fluids.

We conducted laboratory experiments in batch reactors (50 mL glass serum bottles) simulating a wide range of environmental conditions, including pH (~2 to 11), temperature (25 to 75°C), oxidant concentrations, and background fluids (MgCl2 and MgSO4). The resulting solid-phase products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ion chromatography (IC), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Together, these analyses will determine the oxidation extent, product mineralogy, and final fluid composition to identify the most effective Mn(II) oxidant. Ultimately, this will allow us to constrain the specific conditions (oxidant, pH, temperature) under which manganese oxide formation is favored. 

Preliminary results from the experiments have demonstrated substantially faster rates of Mn(II) oxidation in mixed chlorate and bromate systems across all pH conditions. Nitrate, on the other hand, showed no detectable Mn(II) oxidation in any experimental solution investigated. Oxygen showed substantial Mn(II) oxidation at high pH conditions. Scanning electron microscopy reveals that the mineral morphologies of the oxidized products are substantially different in case of Mn(II) oxidation by O2 as compared to oxyhalogens. By comparing Mn(II) oxidation across multiple chemical systems, we constrain the most plausible pathways, oxidants, and environmental conditions responsible for manganese oxide formation on early Mars.

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

doi: 10.1130/abs/2025AM-414503

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