Quartz discovered on Mars, evidence of ancient water circulations

For the past 4 years, the rover Perseverance has been on the surface of Mars, with the aim of understanding the geology of the impact crater Jezero, and sampling well-chosen rocks in preparation for a return to Earth. After studying the magmatic rocks at the bottom of the crater and the sedimentary deposits of an ancient delta deposited above, the rover climbed the walls of the crater. It was then that a series of rocks of very particular chemical and mineralogical compositions were found. They are evidence of a water-rock interaction dating back to the very beginning of Mars’ history.

This discovery was made by an international scientific team thanks to the SuperCam instrumental set. SuperCam was thus able to identify rocks very rich in silica, and composed of different forms of silica: opal (known on Earth for its iridescent properties), chalcedony (a form of quartz with very small crystals), and finally perfectly crystallized quartz. If quartz is common in the Earth’s crust, this is the first time that this mineral has been identified directly on the surface of the red planet, thanks to the Raman spectroscopy deployed by SuperCam. To dissolve and precipitate silica, the existence of hydrothermal processes can be proposed, which are common on Earth at the edges of impact craters. The energy provided by craterization and associated deformation allows heat to flow through the fractured rocks, promoting fluid circulation.

These rocks therefore testify to very old water circulations on Mars and are interesting from an exobiological point of view. Siliceous rocks, and in particular opal, have remarkable abilities to preserve traces of life whether they are morphological or molecular. If Perseverance can sample this type of rock, it will be a prime target to search for signatures of life once brought back to Earth.

« We demonstrate with this publication the presence of different phases of silica, and it is the first identification from the surface of Mars of an “iconic” mineral, quartz, with the most beautiful Raman spectrum ever measured elsewhere on Earth, almost 100 years after the discovery of technology. We also detected other forms of silica: opal and chalcedony. All this highlights a very old hydrothermal system, and these rocks are particularly interesting from an exobiological point of view because silica is a very effective material for preserving signatures of the living world.» says Pierre Beck, professor at the University of Grenoble-Alpes carrying out his research at the Institut de planétologie et d’astrophysique de Grenoble (IPAG). Observing on the surface of Mars traces of an ancient hydrothermal system linked to an impact crater is particularly remarkable, as hydrothermal environments are among the main targets for microbial life research in the Solar System. The surface of Mars is riddled with impacts, and it is quite possible that similar environments may have been fairly common on the red planet.” adds Lucia Mandon, postdoctoral fellow at the National Center for Space Studies (and former LGL-TPE!), also doing her research at IPAG.