The surface of early Mars may have been repeatedly warmed by episodes of intense volcanic activity, according to a study published online in Nature Geoscience. Evidence that liquid water once flowed on the Martian surface has previously been difficult to reconcile with predictions of a cold climate on early Mars.

Itay Halevy and James Head used computer modelling to investigate how sulphur emissions from large volcanic eruptions may have influenced the early Martian climate. In the simulations, emissions of the greenhouse gas sulphur dioxide and the formation of sulphate-coated aerosol particles in a dusty atmosphere led to a net warming effect at the Martian surface. The researchers suggest that volcanism could have temporarily increased the maximum daily temperatures above freezing in low latitude regions and that these conditions could have persisted for periods of tens to hundreds of years.

Intermittent surface melting triggered by volcanism is consistent with previous evidence that the channels and valley networks on ancient Martian terrains were formed during transient wet episodes.