2020.1.11 172. Was There Water on Ancient Mars? Despite Mars's bleak,cold climate today,there is abundant geologic evidence that liquid water once flowed on the Martian surface (and even recent evidence that some water still periodically flows today).The...
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2020.1.11 172. Was There Water on Ancient Mars? Despite Mars's bleak,cold climate today,there is abundant geologic evidence that liquid water once flowed on the Martian surface (and even recent evidence that some water still periodically flows today).The evidence of past flows includes river channels,now dry,that were once carved by powerful foods,valley networks of branching streams and tributaries indicating precipitation falling over wide areas,river deltas and layered sediments suggesting flow into standing bodes of liquid water,and salt and other minerals that dissolved in liquid water and were left behind when water evaporated. When that ancient wet period existed and when it ended is difficult to say. The best method for dating a surface uses radioactivity,the process by which certain elements decay over time.One collects rocks from the surface and measures their radioactive elements to see how much of the decay products have accumulated in the rock since it formed.Transferring
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