Follow the serpentine as a comprehensive diagnostic for extraterrestrial habitability

One of the main goals of most ongoing and future space exploration missions is to search for habitable conditions and potential signs of extraterrestrial life on Solar System bodies. Space Agencies have usually implemented this by ‘following’ a specific diagnostic that has an important role in life, with ‘following the water’ being the most famous — but by no means the only — indication. However, the use of only one life-essential element has limitations. Here we propose to follow the serpentine as a way to integrate multiple aspects of habitable conditions as we know them, given that the presence of serpentine implies a water supply, organic molecules, bioavailable essential elements, energy sources, greenhouse gases and preservable environments. Serpentine minerals are associated with the complex process called serpentinization, a subtype of water–rock interactions. Serpentinization and its products are therefore likely to provide insights into where to find potential life-inhabited niches on celestial bodies such as Mars and icy moons. Serpentinization — the metamorphism of rocks involving large amounts of water — includes many different aspects linked to habitability and offers a more reliable indicator of habitable conditions in the Solar System than a single diagnostic, such as water.