Abstract: Variability in the sulphur isotopic composition in sediments can reflect atmospheric, geological, and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulphur-bearing volcanic gases….