Geological studies have shown that the surface of Mars was shaped by liquid water more than 3 billion years ago. Geomorphological and mineralogical evidence of this aqueous activity (i.e. related to liquid water) comes mainly from observations made on ancient terrain in the southern hemisphere. In contrast, the younger terrain of the Northern Plains shows very few signs of this activity. This indicates a drastic climate change: a little over 3 billion years ago, Mars became a frozen desert where liquid water could no longer exist on the surface. The problem is that it is in these Northern Plains that the scientific community believes Martian oceans once existed... So where are the clues? Are they invisible to our eyes, buried under thick layers of dust and volcanic ash? Or perhaps they never existed? The mystery remains.
Scrutinizing the northern plains of Mars using various NASA and ESA probes orbiting the planet, the research team, which includes numerous French laboratories (see author affiliations below), including LGL-TPE and LAM, has revealed the presence of specific minerals associated with intriguing conical structures. These minerals, in the form of hydrated silica (such as opal, well known on Earth for its iridescent properties) and sulfates (e.g., salts such as gypsum, which form through water evaporation), are evidence of relatively recent (less than 2.5 billion years ago) water activity on the planet’s surface. The discovery of these mineralogical clues has enabled scientists to confirm, for the first time, that the conical structures observed are in fact sedimentary volcanoes (mud or sand volcanoes) that expelled siliceous and/or sulfated material initially buried beneath the surface. This indicates that water reservoirs enriched in silica or sulfates are present at various depths in the planet’s Northern Plains. Studying these minerals reveals the processes at work deep underground and thus allows us to trace the planet’s geological history.
According to calculations made by the planetologists involved in this study, the silica-rich reservoirs could be buried several tens of meters deep. The sulfate reservoirs, buried several hundred meters deep, are therefore older than the former. They could be associated with the deep layers of the Vastitas Borealis Formation (VBF), a geological unit in northern Mars sometimes suggested as a relic of hypothetical ancient Martian oceans. It is therefore possible that these sulfates trace the presence of ancient evaporite deposits, formed by the evaporation of liquid water when Mars was still covered by oceans. These discoveries open up new perspectives for future Mars exploration missions. Indeed, studying these deposits on the surface will make it possible to indirectly sample sedimentary reservoirs buried deep underground, which could provide new clues to tracing the history of liquid water on Mars and settle the ongoing debate about the existence of ancient ocean sediments.
Publication reference
Pineau1,2, M., Carter1,3, J., Lagain4,5,6, A., Ravier7, E., Mangold8, N., Le Deit8, L., Quantin-Nataf2, C., Zanella7, A. (2025). Recent aqueous alteration associated to sedimentary volcanism on Mars. Communications Earth & Environment, 6(1), 800. https://doi.org/10.1038/s43247-025-02713-3Authors’ affiliations
1. Aix Marseille Université , CNRS, CNES, LAM, Marseille, France.2. Université Claude Bernard Lyon 1 , ENS de Lyon, CNRS, LGL-TPE, F-69622 Villeurbanne, France.
3. Institut d’Astrophysique Spatiale, Université Paris Sud, CNRS, Université Paris-Saclay, Orsay, France.
4. Aix Marseille Université, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France.
5. Aix-Marseille Université, Institut ORIGINES, Marseille, France.
6. Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth, Australia.
7. Laboratoire de Planétologie et Géosciences, LPG UMR 6112, CNRS, Le Mans Université, Université Angers, Nantes Université, Avenue Olivier Messiaen, 72085 - Le Mans, France.
8. Nantes Université, Université Angers, Le Mans Université, CNRS, Laboratoire de Planétologie et Géosciences, LPG UMR 6112, 44000 Nantes, France.
Scientific contact
Maxime Pineau
Post-doctoral researcher
maxime.pineau [at] univ-lyon1.fr
Press contact
Béatrice Dias
Communication Chief Officer at Université Claude Bernard Lyon 1
+33 (0)4 72 44 79 98 or +33 (0)6 76 21 00 92
