Mars’ Mysterious Streaks Aren’t Water After All, New Study Finds

For decades, dark streaks snaking down Martian cliffs and crater walls have teased scientists and fueled public imagination. Were these strange features the result of flowing liquid water, hinting at habitable environments on the Red Planet? A new study says: probably not.

A research team analyzing roughly 500,000 slope streaks captured in Mars satellite images has concluded that these formations are most likely created by dry processes, not liquid flows. The findings cast fresh doubt on one of the most debated signs of present-day water on Mars, reinforcing the planet’s image as a cold, dry desert world — at least on the surface.

Dry Dust Mimicking Water’s Behavior

According to Adomas Valantinas, a planetary scientist at Brown University and co-leader of the study published this week in Nature Communications, the streaks are formed when fine Martian dust accumulates on slopes and is then triggered to move by gusts of wind, meteorite impacts, or marsquakes. In Mars’ low-gravity, ultra-dry environment, these tiny dust particles can flow and branch in ways that resemble the behavior of liquids.

“It’s like watching dry sand flow like water when you pour it,” Valantinas explained. “On Mars, the ultra-fine dust and weak gravity amplify this effect, creating these long, sinuous streaks that could easily be mistaken for water flows.”

A Massive Data Dive with AI Support

The researchers combed through 87,000 high-resolution images from NASA’s Mars Reconnaissance Orbiter, collected between 2006 and 2020, identifying slope streaks ranging from 600 to 775 meters in length. These features tended to cluster in Mars’ northern hemisphere, especially in regions like Elysium Planitia, Arabia Terra, and the Tharsis volcanic plateau, home to the colossal Olympus Mons.

Since current satellite resolution limits detection, the team estimates the true number of Martian slope streaks could be closer to two million.

To process this vast dataset, the team applied machine-learning algorithms to identify correlations with factors like temperature, wind patterns, dust levels, and nearby meteor impacts. The conclusion: streaks are strongly associated with dusty regions and dry surface processes, not with evidence of liquid water or frost.

What About Water on Mars?

Water remains essential in the search for extraterrestrial life. Mars is believed to have been warmer and wetter billions of years ago, but today’s surface conditions make liquid water extremely unlikely. While extremely salty brines might persist briefly under specific conditions, this study found little evidence that such processes are responsible for the slope streaks.

The researchers also examined a related Martian phenomenon — recurring slope lineae (RSL) — seasonal streaks that appear in the southern highlands during the summer and fade by winter. These too, the data suggests, are caused by dry processes like dust devils and rockslides rather than liquid water.

“It always comes back to habitability and the search for life,” said study co-leader Valentin Bickel of the University of Bern. “If these streaks had been driven by liquid water, they might have provided a niche for life. Knowing they’re dry helps redirect our search toward places with more promising conditions.”