Chemistry of Meridiani Outcrops

Introduction: The chemistry and mineralogy of the sulfate-rich sandstone outcrops at Meridiani Planum, Mars, have been inferred from data obtained by the Opportunity rover of the MER mission and reported in recent publications [1-6]. Here, we provide an update on more recent samples and results derived from this extensive data set. Compositional Trends: Analyses of the chemistry and mineralogy of outcrops are available in [2], up through the exploration of Endurance Crater. Since leaving this crater, several additional outcrop samples have been analyzed, as float material and as part of larger expanses of exposed outcrop at small craters and in the current position at Erebus crater. The highest sulfur concentration so far encountered at Meridiani is in the Gargarin sample, with SO3 > 27 wt %, Figure 1. This is low-Cl material, in distinction with Cl enrichments in the lower-lying layers in Endurance.