Until now, the exact mineral species behind these hydrous signatures remained uncertain, limiting researchers’ ability to reconstruct the planet’s recent water cycle. Different hydrated phases can form under very different conditions—especially whether they require prolonged liquid water, brief brines, or specific evaporative pathways.

In the new study, the team reports decimeter-scale crystal morphologies with a striking geometry: they resemble euhedral selenite, a distinctive crystal form of gypsum. Euhedral crystals grow from solutions that remain sufficiently stable for ions to organize themselves into ordered lattices, a clue that the rover’s target did not merely “weather” into place.

Why does that matter? Gypsum/selenite is interpreted here as a “primary evaporite,” meaning it precipitated directly from evaporating saline water at or near the surface, rather than being transported or produced by later alteration. The authors contrast this with sulfate deposits already reported on Mars, which may reflect different chemical histories.

Crucially, the paper argues that forming such primary evaporites requires surface water with a cumulative water-equivalent column of at least 6.25–25 meters over time. That estimate links mineral abundance and crystallization needs to plausible water budgets, not just to the presence of hydrated minerals.

But Mars did not have to be wet everywhere at once. The study suggests that either sustained or episodic upwelling of saline groundwater—potentially driven by magmatism—could have fed a very shallow, mostly ice-covered water body. At any particular moment, the actual liquid layer would likely have been about a meter or less.

If true, the setting becomes a chemical time capsule: brine would repeatedly infiltrate the near-surface ice-water interface, evaporate, and deposit new evaporites. Each crystal could therefore archive a sequence of geochemical conditions in the Amazonian period.

Perhaps most exciting, large selenite crystals may preserve fluid inclusions—microscopic pockets of ancient brine sealed within the growing mineral. Those inclusions could retain clues about the composition, salinity, and potential energy sources of Martian fluids, offering an unprecedented window into environments that might have been habitable, at least transiently.

Subject of Research: Mars surface aqueous history and evaporite formation using Zhurong rover observations

Article Title: Primary evaporite in southern Utopia Planitia on Mars from Zhurong rover observations

Article References: Liu, J., Wu, B., Gao, W. et al. Primary evaporite in southern Utopia Planitia on Mars from Zhurong rover observations. Nat Astron (2026). https://doi.org/10.1038/s41550-026-02917-3

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41550-026-02917-3

Keywords: primary evaporite, selenite, gypsum, Zhurong rover, Utopia Planitia, Mars aqueous activity, fluid inclusions, Amazonian water cycle

The dark, finger-like formations known as slope streaks, first detected during NASA’s Viking mission in the 1970s, have intrigued scientists for years. Characterized by their darker color compared to the surrounding Martian terrain, these streaks can extend hundreds of meters down cliff sides and crater walls. Some of these features exhibit longevity, persisting for years or even decades, while others have a more transient existence, appearing and disappearing in sync with the seasonal climate changes of Mars. The recurring slope lineae (RSL)—a subset of these streaks—are particularly intriguing as they consistently reappear in specific locations during the warmest periods of the Martian year.

The long-standing debate among scientists has revolved around the origin of these streaks. While some argue that they are a result of the flow of liquid water, potentially sourced from buried ice or subsurface aquifers, others have posited that these features stem from dry processes, such as landslides or wind-induced activity. The new study led by Adomas Valantinas and Valentin Bickel utilized advanced machine learning algorithms to delve deep into the nature of these slope streaks, ultimately revealing a clearer picture of their origins.

Valantinas, a postdoctoral researcher at Brown, emphasized the importance of understanding modern processes on Mars, including the possibility of minor liquid water flows on its surface. However, the research team’s findings indicated no corroborating evidence to support the liquid water hypothesis. Instead, their machine learning model suggested that slope streaks and RSLs are more likely associated with arid conditions influenced by wind and the movement of dust on steep Martian slopes.

Armed with a comprehensive dataset, the researchers cataloged over 500,000 slope streak features across more than 86,000 high-resolution satellite images, creating the first global map of slope streaks on Mars. This unprecedented effort enabled them to analyze spatial and temporal correlations with various environmental factors such as temperature fluctuations, wind velocity, and dust deposition rates. These correlations painted a picture that hinted at predominantly dry conditions as responsible for the streak formations.

The analysis starkly revealed that typically, both slope streaks and RSLs do not correlate with parameters indicating liquid sources, such as specific slope orientations or high humidity levels. On the contrary, their formation events seemed strongly linked with heightened wind speeds and abundant dust activity, hinting at dry mechanisms like sudden avalanches of dust rather than liquid flows. Such findings have substantial implications for our understanding of Mars’s climatic systems and its historical geology.

The researchers proposed that the streaks could originate when layers of fine dust are dislodged from steep surfaces. Factors such as recent impacts and geological disturbances appear to play a pivotal role, where shockwaves from impacts may disturb surface dust, or localized wind disturbances, such as dust devils, could contribute to the dust movement. This understanding challenges previous notions regarding the habitability of slope streak sites and raises critical awareness regarding the implications for future Mars exploration missions.

For NASA and other exploring entities, the findings from this study provide invaluable insights. The notion that slope streaks may not represent potential habitable environments mitigates some concerns associated with biocontamination risks during exploration. If these regions do not harbor liquid water, the likelihood of risking contamination from Earthly organisms during missions to Martian surface sites diminishes.

Overall, the implications of this research broaden our comprehension of Martian landscapes and challenge previous paradigms about the potential for life beyond our planet. The prospects of liquid water on the Martian surface, long deemed a possibility, now face significant challenges regarding their viability. As technologies advance and further research is conducted, it is becoming increasingly essential to adopt a more nuanced approach to understanding the complex geological processes at work on Mars.

In conclusion, this innovative use of machine learning offers a promising avenue for researchers, aiding the effort to parse out competing hypotheses about Mars’s geomorphology. As we continue to decipher the enigmatic features of the Martian landscape, it is vital to remember that each new discovery holds the potential to reshape our understanding of life in the universe. This study sheds new light on the processes that shape Mars and raises pertinent questions about the planet’s ability to support life, thus highlighting the ongoing need for robust research and exploration.

Subject of Research: Slope Streaks on Mars
Article Title: New Insights into Martian Slope Streak Formation: No Evidence of Water
News Publication Date: May 19, 2025
Web References: DOI Link
References: Nature Communications
Image Credits: NASA

Keywords: Mars, slope streaks, RSL, liquid water, dry processes, machine learning, geology, planetary science.