IRON-SULFUR CONTAINING MINERAL PHASE IDENTIFIED IN JEZERO’S NORTHERN MARGIN UNIT WITH SUPERCAM LIBS DATA AND SPECTRAL UNMIXING

Abstract

The SuperCam LIBS (laser-induced breakdown spectroscopy) instrument is part of the rover’s payload and collects data on the martian surface from remote distances of up to several meters. Sulfur is an element that is generally challenging to detect and quantify using LIBS but its emission features can be identified and quantified in targets with high sulfur content, such as Ca-sulfates and Mg-sulfates. High sulfur in SuperCam LIBS data was observed at the delta front in several targets containing Ca-sulfates, which were identified as anhydrite using SuperCam Raman data. At Bright Angel in Neretva Vallis, high sulfur was again seen together with high calcium, indicating again the presence of Ca-sulfates that was consistent with findings of other rover techniques. The sulfur emission lines in LIBS data are strongly superimposed by Fe lines and are particularly difficult to interpret in targets with significant iron content, complicating the analysis of mineral phases with both iron and sulfur. Spectral unmixing (SU) provides a new and alternative way to analyze LIBS data to obtain semi-quantitative values for major and minor elements. In particular, sulfur scores can be obtained, unmixed from the contribution of iron in the spectra. In this work, we present the results of SU applied to SuperCam LIBS data, reporting the detection of a mineral phase enriched in both sulfur and iron, with most detections occurring in a few targets in the northern part of the Margin Unit of Jezero crater’s western fan.