Mars Might Host a Planetwide Subsurface Water Network

A study of 24 enclosed Martian craters in the northern hemisphere finds evidence for a planetwide groundwater system that persisted after surface water declined, with water migrating into deep, interconnected underground reservoirs likely fed by a vast ancient ocean about 3–4 billion years ago. Minerals such as clays and carbonates at several sites suggest habitable conditions in the subsurface and the potential preservation of biosignatures in buried sediments.