Research results suggest that the black streaks observed on the cliffs of the 'Red Planet' Mars may be traces left by wind and dust rather than the water previously thought. This finding could significantly influence the direction of Mars exploration by putting a damper on the belief that water could still flow on Mars.
A joint research team from Brown University in the United States and the University of Bern in Switzerland noted on the 19th that "the stripes formed on the Martian slopes were confirmed to be created by wind and dust rather than water through large-scale analysis utilizing artificial intelligence (AI)." The research results were published in the international journal 'Nature Communications' on the same day.
The stripes on the Martian surface were first captured by the National Aeronautics and Space Administration (NASA) Viking spacecraft in the 1970s. The stripes appear darker than the surrounding area and extend along the slopes of cliffs or craters for over hundreds of meters. Some stripes persist for several years to decades, while others appear and disappear more rapidly. In particular, the stripes that repeatedly form during warm periods are referred to as "Recurring Slope Lineae (RSL)."
Scientists have continued to debate the nature of the stripes. As claims arose that the stripes were marks left by seasonal melting of ice mixed with salt underground, the possibility of life existing on Mars was suggested. Conversely, there were also arguments that they were the result of dry phenomena such as rockfalls or dust storms.
The research team analyzed 86,000 satellite images using machine learning and mapped over 500,000 stripe data based on this analysis. Machine learning is an AI technology that learns from large amounts of data and finds methods autonomously without being pre-programmed.
After training the AI, various conditions such as wind, temperature, humidity, and the likelihood of rockfalls were compared and analyzed. As a result, it was revealed that the stripes appear more frequently in areas where strong winds and dust accumulation occur rather than in conditions related to water, such as temperature, humidity, and topographical direction.
Dr. Adam Valantinas from Brown University said, "Finding evidence of water on the Martian surface was the main research goal, but we have not found sufficient evidence to support this. The results analyzed by AI further support the hypothesis that the formation of the stripes is due to dry processes."
In fact, the stripes frequently appear in areas where there have been recent meteorite impacts or where rockfalls or dust whirlwinds are active. The research team explained, "The likelihood of these stripes forming is greatest when fine dust layers suddenly slide down steep inclines, and they have been observed more frequently near recent impact craters, as shock waves can shake and dislodge surface dust."
These research results could influence future Mars exploration strategies. If areas with stripes are unrelated to water, they could be more freely accessible due to a lower risk of biological contamination. Until now, exploration was restricted in regions where life could potentially exist on Mars, as terrestrial microorganisms carried on exploration equipment could affect Martian life.
Dr. Valantinas stated, "This research demonstrates the advantages of a big data-based approach, allowing us to filter out unlikely theories before sending a spacecraft directly."
References
Nature Communications (2025), DOI: https://doi.org/10.1038/s41467-025-59395-w