Investigating co-occurences of gypsum veins and magnesium sulfates in the Rio Puerco necks region as a geochemical proxy for sulfate origin on Mars
— Anna Szynkiewicz and Ettenborough, Ivy, Smith, Sara M., Vaniman, David, [eds.]

Abstract—In Gale crater on Mars, abundant secondary calcium (Ca) and magnesium (Mg) sulfate minerals are common as veins and cement in the sedimentary strata of Mount Sharp. However, the climate and source of aqueous sulfate (SO₄^2-) during their formation are not well understood. Our δ³⁴S analysis of surficial deposits in the Rio Puerco necks region show that oxidation of bedrock sulfides with negative δ³⁴S (-37 to -6‰) leads to abundant formation and co-occurrence of Ca-sulfate veins and Mg-sulfate-rich salt with similar negative δ³⁴S values (-33 to -13‰). Additionally, the negative δ¹⁸O values of SO4 2- (-7 to +3‰) and gypsum hydration water (-9 to +1‰) are consistent with local meteoric precipitation, implying their origin from shallow water-rock interactions. Our geochemical comparisons between the Rio Puerco necks region and Gale crater strongly suggest the importance of sulfide weathering and short-lived water activity under a dry climate in the past on Mars.