A Geologic Model for Eridania Basin on Ancient Mars

This diagram illustrates an interpretation for the origin of some deposits in the Eridania basin of southern Mars as resulting from seafloor hydrothermal activity more than 3 billion years ago.

The ground level depicted is an exaggerated topography of a transect about 280 miles (450 kilometers) long. Blue portions of the diagram depict water-depth estimates and the possibility of ice covering the ancient sea.

Thick, clay-rich deposits (green) formed through hydrothermal alteration of volcanic materials in deep water, by this model. Notations indicate deep-water reactions of iron and magnesium ions with silicates, sulfides and carbonates. Deep-seated structural discontinuities could have facilitated the ascent of magma from a mantle source. Chloride deposits formed from evaporation of seawater at higher elevations in the basin.

This graphic was included in a 2017 report "Ancient hydrothermal seafloor deposits in Eridania basin on Mars" in Nature Communications.