Volcanic sulfur on MarsWas Mars ever warm enough to support life? Reduced sulfur refers to sulfur atoms in a negative oxidation state, forming compounds like hydrogen sulfide (H2S) and thiols (mercaptans). Volcanic emissions of reactive sulfur gases on early Mars may have contributed to a greenhouse effect, potentially creating conditions favorable for liquid water and microbial life. Bellino said:This indicates that sulfur cycling – the transition of sulfur to different forms – may have been a dominant process occurring on early Mars. In addition, they will investigate whether microbes could have used reduced sulfur as a food source.