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CBS News
20-05-2025
- Science
- CBS News
New study suggests scientists were wrong about dark streaks on Mars
A new study casts doubt on a phenomenon that was previously believed to show water flowing on the surface of Mars. Since the 1970s, scientists have studied dark streaks seen on Mars' cliff sides and crater walls. The streaks tend to be hundreds of meters long. Some can last for a long time, while others are more short-lived. Those more short-lived slope streaks, called recurring slope lineae, or RSLS, tend to recur in the same areas from year to year, according to a news release announcing the study. Some scientists believe the streaks are proof of flowing water on the planet and could suggest the Red Planet is home to habitable environments. Others believe the streaks are caused by dry processes, like rock falls or wind gusts, and said the streaks only appear like liquid remnants because scientists are studying orbital images. Adomas Valantinas, a postdoctoral researcher at Brown University, and Valentin Bickel, a researcher at Switzerland's University of Bern, used machine learning to study the streaks. The process cataloged more than 86,00 high-resolution satellite images of the slope streaks and RSLs. That created a first-of-its-kind global Martian map showing more than half a million such features. Slope streaks extend across Mars' Arabia Terra, as captured by the European Space Agency's Trace Gas Orbiter. NASA "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." Bickel said. "Then we could look for correlations over hundreds of thousands of cases to better understand the conditions under which these features form." The analysis, published in Nature on Monday, found that the slope streaks were not "generally associated with factors that suggest a liquid or frost origin," according to the news release. Such factors would include a specific orientation of slopes, high humidity or surface temperature fluctuations. What the study did find was that the slopes were more likely to form in places that had above-average wind speeds and dust deposition, likely pointing to a dry origin. The slope streaks were more often found near recent-impact craters and could be caused when shockwaves shake surface dust. RSLs are more common in areas with frequent rockfalls or dust devils. "Our study reviewed these features but found no evidence of water. Our model favors dry formation processes," Valantinas said. The results of the study cast doubt on claims that slope streaks could be signs of habitable regions. That means that researchers could send rovers or other spacecraft to explore the areas without contaminating the sites. "That's the advantage of this big data approach," Valantinas said. "It helps us to rule out some hypotheses from orbit before we send spacecraft to explore."
The Herald
20-05-2025
- Science
- The Herald
Study casts doubt on water flows as cause of streaks on Martian slopes
"It's similar to how dry sand can flow like water when poured. But on Mars, the ultra-fine particles and low gravity enhance the fluid-like properties, creating features that might be mistaken for water flows when they're dry material in motion," Valantinas said. The study examined about 87,000 satellite images, including those obtained between 2006 and 2020 by a camera aboard Nasa's Mars Reconnaissance Orbiter, of slope streaks, which form suddenly and fade over years. They average roughly 600m to 775m long, sometimes branching out and going around obstacles. The slope streaks were concentrated mostly in the northern hemisphere, particularly in three major clusters: at the plains of Elysium Planitia, the highlands of Arabia Terra and the vast Tharsis volcanic plateau including the Olympus Mons volcano, towering about three times higher than Mount Everest. The researchers said limitations in the resolution of the satellite images mean they account for only a fraction of slope streaks. They estimated the number at up to two million. Water is considered an essential ingredient for life. Mars billions of years ago was wetter and warmer than it is today. The question remains whether Mars has any liquid water on its surface when temperatures seasonally can edge above the freezing point. It remains possible that small amounts of water, perhaps sourced from buried ice, subsurface aquifers or abnormally humid air, could mix with enough salt in the ground to create a flow even on the frigid Martian surface. That raises the possibility that the slope streaks, if caused by wet conditions, could be habitable niches. "Generally, it is very difficult for liquid water to exist on the Martian surface due to the low temperature and the low atmospheric pressure. But brines, or very salty water, might potentially be able to exist for short periods of time," said planetary geomorphologist and study co-leader Valentin Bickel of the University of Bern in Switzerland. Given the massive volume of images, the researchers employed an advanced machine-learning method, looking for correlations involving temperature patterns, atmospheric dust deposition, meteorite impacts, the nature of the terrain and other factors. The geostatistical analysis found slope streaks often appear in the dustiest regions and correlate with wind patterns, while some form near the sites of fresh impacts and quakes. The researchers also studied shorter-lived features called recurring slope lineae, or RSL, seen primarily in the Martian southern highlands. These grow in the summer and fade the next winter. The data suggested these also were associated with dry processes such as dust devils, or whirlwinds of dust, and rockfalls. The analysis found both types of features were not typically associated with factors indicative of a liquid or frost origin such as high surface temperature fluctuations, high humidity or specific slope orientations. "It all comes back to habitability and the search for life," Bickel said. "If slope streaks and RSL would be driven by liquid water or brines, they could create a niche for life. However, if they are not tied to wet processes, this allows us to focus our attention on other, more promising locations." Reuters )
