Sulfur species in alh 84001 carbonates constraining conditions of water on ancient mars

Introduction: Geological and geomorphological evidence suggests the presence of liquid water on the Martian surface in the past [1]. A 4.1-billion-year old (Ga) Martian meteorite, Allan Hills (ALH) 84001 [2], has trace amounts of carbonates (ALH carbonates) that are interpreted to have formed from Martian nearsurface fluids at ~3.9 – 4.0 Ga [3, 4]. The carbonates have characteristic structures with Mg-Fe-Mn-Ca chemical zoning that reflects the compositions of the co-existing fluids [5]. Sulfur (S), a redox sensitive element (valence state of –2 to +6), is a promising tracer for constraining the oxidation process. The objective of this study is to determine a possible redox condition of the aqueous fluids at the 4 Ga Martian near-surface system. Here we conducted X-ray absorption near edge structure (μ-XANES) analyses to investigate the sulfur species in carbonates of ALH 84001.