Fossilized wrinkles in impact craters suggest once again that water might once have flowed on Mars — this time, beneath the surface.
Water on Mars has been "discovered" many times in recent years. Clay deposits, meteorite evidence, dark rivulets flowing down Sunward-facing crater walls, and many more bits of evidence all point to a past, and possibly a present Mars with liquid water flowing on its surface.
Now it seems water might once have flowed beneath the surface too, putting Mars in the underground-water club with Europa and Enceladus. The evidence for an underground water system comes from ridges, well-known, but not well understood structures seen in Martian crater fields.
Lee Saper and Jack Mustard (Brown University) mapped out 4,000 ridges, using the Mars Reconnaissance Orbiter to take wide-field shots as well as detailed close-ups of two crater fields called Nili Fossae and Nilosyrtis. They found that the ridges weakly aligned, suggesting that they were wrinkles caused by impact craters. But how have they stood the test of time, when the surrounding land has been eroded by wind and dust? Saper and Mustard suggest that when impacts fractured the ground, underground water flowed into the cracks, depositing minerals in their wake. Mars has no Drano to clear the pipes, so the minerals built up over time, fossilizing the evidence for water as the surrounding land eroded away.
Is this result shocking? No. Some might say that the evidence for a wet Martian past became clear in 1971 with Mariner 9 images of "flow features" on the surface. But what's interesting is that the two crater fields examined by Saper and Mustard fall right on the edge of Utopia — the Utopia Planitia, that is. The Utopia Planitia lies within the great Vastitas Borealis, the low-lying plains that cover much of Mars's northern hemisphere. One controversial theory suggests that Vastitas Borealis was filled by an ancient ocean some 4 billion years ago, and previous studies have suggested that some of that water may have gone underground.
BROWN UNIVERSITY RELEASE:
Ridges on Mars suggest ancient flowing water
Networks of narrow ridges found in impact craters on Mars appear to be the fossilized remnants of underground cracks through which water once flowed, according to a new analysis by researchers from Brown University. . . . Read the full press release.