The Red Planet is wet, scientists announced today. New evidence from NASA’s Mars Reconnaissance Orbiter (MRO) confirms that suspicious dark streaks on Mars that appear and disappear with the seasons are created by flowing liquid water. The streaks are made by salty water that runs down steep hills during warm months, when temperatures are above –23 degrees Celsius, and freezes during colder times.
The intriguing streaks, called recurring slope lineae, were first spotted in 2010 in images from the MRO’s HiRISE (High-Resolution Imaging Science Experiment) camera. Scientists have long suspected that the streaks marked the location of liquid water. Now researchers have found the chemical signatures of hydrated minerals on these slopes, confirming that explanation. The new evidence also comes from the MRO via CRISM, its Compact Reconnaissance Imaging Spectrometer for Mars, which separates light into its constituent wavelengths to reveal the chemicals present on the Martian surface. The instrument saw the signatures of magnesium perchlorate, magnesium chlorate and sodium perchlorate—all hydrated salts that require water to form and also contain it. The chemicals appear in the summer, when the dark streaks are visible, and disappear along with the features when temperatures drop. “This is the best evidence of liquid water on Mars in the present day,” says Georgia Institute of Technology scientist James Wray, co-author of a paper reporting the data published today in Nature Geoscience. “The fact that these chemicals are sitting on these flows and concentrated there and have water means there’s really no way that water wasn’t involved.” (Scientific American is part of Nature Publishing Group.)
The intriguing streaks, called recurring slope lineae, were first spotted in 2010 in images from the MRO’s HiRISE (High-Resolution Imaging Science Experiment) camera. Scientists have long suspected that the streaks marked the location of liquid water. Now researchers have found the chemical signatures of hydrated minerals on these slopes, confirming that explanation. The new evidence also comes from the MRO via CRISM, its Compact Reconnaissance Imaging Spectrometer for Mars, which separates light into its constituent wavelengths to reveal the chemicals present on the Martian surface. The instrument saw the signatures of magnesium perchlorate, magnesium chlorate and sodium perchlorate—all hydrated salts that require water to form and also contain it. The chemicals appear in the summer, when the dark streaks are visible, and disappear along with the features when temperatures drop. “This is the best evidence of liquid water on Mars in the present day,” says Georgia Institute of Technology scientist James Wray, co-author of a paper reporting the data published today in Nature Geoscience. “The fact that these chemicals are sitting on these flows and concentrated there and have water means there’s really no way that water wasn’t involved.” (Scientific American is part of Nature Publishing Group.)