Mars, the enigmatic Red Planet, has long fascinated scientists and explorers alike. Among its diverse geological features, thick deposits of clay stand out as critical markers of the planet’s ancient environment. These clay layers, sometimes stretching hundreds of feet deep, offer a window into Mars’ distant past when water was prevalent on its surface. For decades, researchers have speculated about the origins of these clays and their implications for past habitability, but many questions remained unanswered—until now.
In a groundbreaking study published in Nature Astronomy, a team of scientists from The University of Texas at Austin presented an in-depth analysis of these Martian clay-rich landscapes, revealing that the majority formed adjacent to long-standing bodies of surface water. This finding suggests that ancient Mars hosted vast, stable lakes or shallow seas where water persisted over extended periods, fostering intense chemical weathering processes. Such conditions could have created the ideal setting for life to emerge and evolve, supported by the availability of water, minerals, and a relatively tranquil environment shielded from physical disturbances.
The research, spearheaded by Rhianna Moore during her postdoctoral fellowship at the Jackson School of Geosciences, employed detailed imaging and topographical analyses of over 150 known clay deposits identified by NASA’s Mars Reconnaissance Orbiter. Moore’s meticulous mapping revealed a strong correlation between low elevation clay deposits and ancient lake beds, while these deposits were conspicuously absent near valley networks characterized by more vigorous water flow and erosion. This spatial distribution points to a delicate environmental balance—conditions favoring chemical weathering without excessive physical erosion, crucial for the preservation of thick, mineral-rich clay horizons.
Co-author Tim Goudge, an assistant professor at the UT Jackson School, drew parallels between these Martian environments and certain tropical regions on Earth, where thick clay layers accumulate due to humid, stable climates with minimal physical erosion. On our planet, these regions typically feature slow-moving water bodies coupled with abundant chemical reactions that transform primary minerals into clays. The similarity suggests that although ancient Mars was vastly different from Earth today, some fundamental geochemical and hydrological processes might have operated in analogous ways.
One particularly intriguing aspect of this study lies in its revelations about Mars’ ancient water-carbon cycle. Unlike Earth, where the tectonic activity constantly recycles crustal rocks and exposes fresh surfaces for weathering, Mars shows no clear evidence of plate tectonics. This absence had dramatic consequences for the planet’s climate and geological pathways. When volcanic eruptions on Mars emitted carbon dioxide (CO₂), the lack of fresh, reactive volcanic rock meant that this greenhouse gas accumulated in the atmosphere rather than being efficiently sequestered in carbonate minerals as it often is on Earth.
The Martian clays themselves may have played a role in this imbalance. By absorbing water and binding chemical byproducts within their mineral matrix, these extensive clay deposits potentially inhibited the formation of carbonate rocks, which would otherwise have formed through reactions between CO₂, water, and fresh volcanic substrates. This phenomenon could explain the long-standing enigma of Mars’ sparse carbonate record, despite geological and atmospheric conditions that should favor their presence.
The implications of this balanced but complex chemical environment are profound. Not only do the thick clay layers attest to a wetter, more habitable Mars billions of years ago, but they also underline how the planet’s geological and atmospheric evolution diverged sharply from Earth’s. The stable nature of those clay-rich lowlands—with limited topographic upheaval—would have provided a refuge where early life could have taken root, shielded from the harsh fluctuations witnessed elsewhere on the planet.
This deeper understanding of Mars’ ancient surface conditions also feeds into ongoing debates about where to look for biosignatures in the search for past life. Unlike disruptive and erosive valley networks, these stable lacustrine environments are prime candidates for the preservation of organic molecules and microbial fossils. Their chemical composition, approachable via rover missions or sample return missions, may hold the keys to unraveling Mars’ biological past.
Furthermore, the study sheds light on the climatic narrative of early Mars. Billions of years ago, the Red Planet experienced conditions capable of sustaining liquid water on its surface—a significant departure from the cold, arid world we observe today. The presence of long-lasting lakes capable of promoting clay formation suggests a climate warm enough for water to remain stable for extended durations, driven by a thicker atmosphere rich in greenhouse gases like CO₂.
Yet, devoid of tectonic recycling, Mars’ geological processes entered a state of stasis. Without new rock exposures, chemical weathering processes slowed down, allowing greenhouse gases to accumulate unchecked and causing climate conditions that, while warmer and wetter than today, also gradually transitioned into the cold desert Mars we recognize. The clays, therefore, stand as silent witnesses to an intermediate phase in Mars’ environmental history, bridging the wet ancient past and the harsh present.
This research was made possible through the comprehensive global surveys conducted by NASA’s Mars Reconnaissance Orbiter and advances in remote sensing technologies that enable detailed assessments of mineralogical compositions from orbit. The mapping of aluminum-bearing clays, for example, alongside iron and magnesium clays, provides useful proxies for ancient aqueous chemistry and sedimentation patterns.
Moreover, the study exemplifies interdisciplinary collaboration, merging planetary geology, geochemistry, and climatology to forge a comprehensive narrative of Mars’ ancient landscape dynamics. As Moore moves forward in her career with NASA’s Artemis program, the insights gained from this research continue to inspire new explorations not only on Mars but also on celestial bodies across the solar system where water-rock interactions might hint at life-forming processes.
With NASA and the Canadian Institute for Advanced Research supporting this work, it marks a significant stride in our understanding of planetary habitability beyond Earth. The findings emphasize that Mars, once a seemingly desolate neighbor, was a complex and potentially life-friendly world marked by stable environments conducive to chemical weathering and clay formation. As missions like Perseverance and upcoming sample returns continue to probe the Red Planet, such knowledge lays critical groundwork for identifying promising sites for future exploration and, possibly, evidence of ancient extraterrestrial life.
Subject of Research:
Not applicable
Article Title:
Deep chemical weathering on ancient Mars landscapes driven by erosional and climatic patterns
News Publication Date:
16-Jun-2025
Web References:
https://www.nature.com/articles/s41550-025-02584-w
http://dx.doi.org/10.1038/s41550-025-02584-w
Image Credits:
NASA/JPL-Caltech/UArizona
Keywords:
Mars, Landscape evolution, Space weathering, Sediment, Physical geology, Hydrology, Clays, Soils, Porous materials
