An international research team comprising scientists from CNRS Terre & Universe and CNRS Physique (including LATMOS-IPSL) has identified clear rocks rich in alumina (Al₂O₃), a compound rarely found in such high concentrations on Mars. These rocks contain minerals such as kaolinite, a clay formed by intense aqueous alteration, and dehydrated phases, including spinel-type minerals.

They bear witness to extreme alteration by water, probably during the ancient periods of Mars, around 3.8 to 4 billion years ago, when humid conditions prevailed. The water would have dissolved elements such as iron and magnesium, leaving a high concentration of aluminium. Subsequently, these rocks were exposed to high temperatures, possibly as a result of meteorite impacts or volcanic processes, leading to partial dehydration and hardening.

The Chignik rock, captured by the Mastcam-Z instrument and analysed by SuperCam on board Perseverance, contains the highest concentration of kaolinite ever observed by a rover on Mars. © Reference

These rock fragments, scattered around the Jezero crater, could have come from the crater rim, eroded by fluvial phenomena or impacts. Their discovery is significant because kaolinite and other similar clays are markers of a once habitable environment. It demonstrates that Mars underwent complex geological processes comparable to those observed on Earth, and confirms that water played a crucial role in transforming its landscape.

Scientists hope that the study of these rocks will provide a better understanding of the ancient climatic conditions on Mars, as well as the mechanisms that may have supported possible microbial life. These samples are also considered a priority target for return to Earth on future missions, as they could contain valuable clues about the geological and climatic history of Mars.

In summary, these alumina-rich rocks represent the most pronounced signs of aqueous alteration ever observed in-situ on Mars. They shed light on the planet’s wet periods and pave the way for new research into the possibility of past life on the Red Planet.

The SuperCam instrumental ensemble

This highly innovative instrument was developed jointly by a consortium of French laboratories led by IRAP (Toulouse, France) and LANL (Los Alamos, USA), with a contribution from the University of Valladolid (Valladolid, Spain). CNES is responsible to NASA for the French contribution to SuperCam. CNES, CNRS and a number of universities have contributed human resources for the supply of this instrument, and the instrument is operated alternately by the American team from LANL and by the French and European team through the control centre installed at CNES in Toulouse (FOCSE Mars 2020).

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CNRS Laboratories

• Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS-IPSL, CNRS/Sorbonne Univ/UVSQ)
• Institut de Recherche en Astrophysique et planétologie (IRAP-OMP, CNRS/CNES/Univ. Toulouse III Paul Sabatier)
• Institut de planétologie et d’astrophysique de Grenoble (IPAG-OSUG, CNRS/UGA)
• Laboratoire de Géologie de Lyon : Terre, Planètes, Environnement (LGL-TPE-OSUL, CNRS/ENS Lyon/Univ. Claude Bernard/UJM Saint-Étienne)
• Laboratoire d’Instrumentation et de Recherche en Astrophysique (LIRA-Obs de Paris-PSL, CNRS/Observatoire de Paris-PSL/Sorbonne Univ/Univ Paris Cité)
• Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC, CNRS/MNHN/Sorbonne Univ.)

Reference

Royer, C., Bedford, C.C., Johnson, J.R. et al. Intense alteration on early Mars revealed by high-aluminum rocks at Jezero crater. Commun Earth Environ 5, 671 (2024).

Source: CNRS Terre & Univers.