Quartz discovered for the first time on Mars by the Perseverance robot, attesting to ancient water circulation on the red planet

For the past 4 years, the Perseverance rover has been surveying the surface of Mars, with the aim of understanding the geology of the Jezero impact crater, and sampling selected rocks with a view to returning to Earth. After studying the magmatic rocks on the crater floor and the sedimentary deposits of an ancient delta deposited on top of them, the rover climbed the crater ramparts. A series of rocks with very specific chemical and mineralogical compositions were found. They bear witness to water-rock interaction dating back to the very beginning of Mars' history.

This discovery was made by an international scientific team using the SuperCam2 instrument package. SuperCam was able to identify rocks that are 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. While quartz is common in the Earth's crust, this is the first time 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, as these are common on Earth at the edges of impact craters. The energy supplied by cratering and associated deformation provides heat, promoting fluid circulation within the fractured rocks.

These rocks therefore bear witness to very ancient water circulation on Mars, and are interesting from an exobiological point of view. Siliceous rocks, and opal in particular, have a remarkable capacity to preserve traces of life, whether morphological or molecular. If Perseverance succeeds in sampling this type of rock, it will be a prime target for the search for signatures of life once brought back to Earth.