44 Advancing Mineral Science and Exploring Planetary Surfaces: In Honor of MSA Dana Medalist, Elizabeth B. Rampe, Part II

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

Sunday, 19 October 2025
1:30 PM - 5:30 PM
HBGCC, 214C

Measuring Sulfur on Mars: APXS, Sulfates and Elemental Sulfur at Gale Crater

Paper number: 44-6
Program: Technical Sessions
Time: 2:55 PM – 3:10 PM

Authors

Abstract

Sulfur is a major element on the martian surface, having been detected both from landed and orbital missions. Understanding the associated mineralogy and its distribution has implications for past climate and aqueous conditions. Gale crater was selected as the Mars Science Laboratory (MSL) landing site owing to orbital signatures within its 5 km high central mound (Aeolis Mons, informally Mount Sharp), which are consistent with a transition from clay- to hydrated Mg-sulfate-dominated mineralogies. This transition was hypothesized to indicate a drying out event, possibly related to a global change in Mars environment at this time. 

The Canadian-built and funded Alpha Particle X-ray Spectrometer (APXS) on the Curiosity rover uses a combination of Particle-Induced X-ray Emission and X-ray Fluorescence to determine the chemistry of rocks, powdered drill fines, unconsolidated materials, and argon in the atmosphere. Elemental abundances for Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Zn and Br are quantified and reported as weight% oxides except for Cl (element%) and Ni, Zn, and Br (parts per million). Detection limits for all elements are <0.5 wt%. Thus, APXS can accurately measure and track sulfur abundances along Curiosity’s traverse. Correlations with other elements (e.g., Ca and Mg) and intensities of elastically and inelastically scattered X-rays indicative of light element concentrations (e.g., oxygen), can be used to infer mineralogy of the S-bearing phases. We report the key findings of APXS sulfur analyses along the >35 km traverse and >500 m of elevation. Highlights include: 1) the occurrence of abundant and widespread CaSO4 veins; 2) low S bedrock dominating the base of the section (Bradbury grp) and Stimson formation sandstones; 3) transition from bedrock dominated by variation in the abundance of CaSO4 phases to strata (Layered Sulfate unit – LSu) exhibiting addition of ~10wt% MgSO4 phases, coincident with hydrated Mg-sulfate orbital signatures within the Mount Sharp grp; 4) identification of MgSO4-rich diagenetic nodules and resistant features; and 5) the unexpected discovery of native sulfur within the late stage, Gediz Vallis debris flow/avalanche deposit. Current exploration of the boxwork terrain has revealed changes in S and Mg relative to the LSu, consistent with decreasing MgSO4. We will place these findings in context and discuss the implications of the S-bearing phases detected by APXS.

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

doi: 10.1130/abs/2025AM-414286

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.