A groundbreaking study published in Nature Communications has cast new doubt on the idea that the dark streaks observed on Martian slopes are signs of liquid water flowing on Mars today. For decades, these streaks, known as recurring slope lineae (RSL), have intrigued scientists as potential evidence for present-day water activity and possibly habitable environments. However, researchers from Brown University and the University of Bern have applied machine learning techniques to analyze a vast dataset of these features, concluding that the streaks are most likely caused by dry dust avalanches triggered by wind and impact events, rather than flowing water. This insight significantly changes how scientists understand the current processes shaping the Martian surface.
Dry Dust Avalanches Are Responsible for Mars’ Slope Streaks, Not Water
“A big focus of Mars research is understanding modern-day processes on Mars—including the possibility of liquid water on the surface,” said Adomas Valantinas, a postdoctoral researcher at Brown who coauthored the study with Valentin Bickel of the University of Bern. The streaks on Mars have been observed for nearly 50 years, first seen in Viking mission images from the 1970s. These dark features appear on steep slopes, often extending for hundreds of meters and lasting from days to years. Although some scientists previously proposed that they might form from salty liquid water flowing briefly on Mars’ surface, the planet’s cold and dry environment makes stable liquid water extremely unlikely under current conditions. The new research supports an alternative explanation: that layers of fine dust suddenly slide down steep slopes, creating dark streaks without any involvement of liquid water.
Machine Learning Unveils Global Patterns Behind Streak Formation
To better understand these mysterious streaks, the researchers used a machine learning algorithm to scan more than 86,000 high-resolution images, identifying over 500,000 slope streak features worldwide on Mars. “Once we had this global map, we could compare it to databases and catalogs of other things like temperature, wind speed, hydration, rock slide activity and other factors,” said Valentin Bickel. By examining such a large dataset, the team could statistically analyze correlations between streak occurrences and environmental conditions. Their findings revealed that these streaks do not correspond with factors that would support water or frost origins, such as temperature peaks or high humidity. Instead, they found strong links between streak formation and increased wind activity and dust deposition, pointing toward dry, granular flow processes as the primary cause.
Implications for Mars Exploration and Search for Life
The new findings have significant implications for the ongoing exploration of Mars, particularly in the search for life. If slope streaks and RSLs are not caused by liquid water, then these areas are unlikely to be habitable environments for microbes. This reduces the risk of contaminating potentially life-supporting sites with Earth-based microbes unintentionally transported by spacecraft. “That’s the advantage of this big data approach,” said Valantinas. “It helps us to rule out some hypotheses from orbit before we send spacecraft to explore.” With this improved understanding, future missions can better prioritize exploration targets, focusing on areas more likely to contain signs of past or present life. Additionally, the study underscores the dynamic role of wind and dust in shaping Mars’ surface and climate today.
