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Ancient Lake on Mars turned salty for a spell, Curiosity Rover finds

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NASA's Curiosity Mars rover may have just captured a snapshot of the Red Planet's long-ago Great Drying. Curiosity has detected relatively high levels of sulfate salts in the rocks of Gale Crater, a new study reports. Gale hosted a lake-and-stream system in the ancient past, and the newfound salts were likely concentrated by evaporation during a period of low water levels, researchers said. This period may have been part of a normal cyclical fluctuation, a regular climatic change perhaps driven by recurring shifts in Mars' axial tilt or orbital parameters. "Alternatively, a drier Gale lake might be a sign of long-term, secular global drying of Mars, posited based on orbital observations," the scientists wrote in the new study, which was published online today (Oct. 7) in the journal Nature Geoscience.


Mars was once a relatively warm and wet world, complete with rivers and lakes and, most researchers believe, an ocean covering a large swath of the planet's northern hemisphere. But things began to change around 4.2 billion years ago. Mars lost its global magnetic field, which had protected the planet's atmosphere from the solar wind, the stream of charged particles flowing continuously from the sun. As a result, Mars lost the vast majority of its air to space by about 3.7 billion years ago, causing the planet to become much colder and drier. Today, Mars' air is just 1% as dense as Earth's atmosphere at sea level. (Luckily for us, Earth still has its global magnetic field.)

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