ripples
January 24, 2014
A piece of Mars: On Oct. 15, 2013, Curiosity drove past a crater that has small dunes or ripples on its floor. In a new HiRISE image, you can see Curiosity’s tracks from that day (its 424th sol on Mars). […]
January 13, 2014
A piece of Mars: Where the wind blows strong and there’s a lot of sand, the surface gets scoured. Some bits of the ground, called yardangs, are more resistant and stick around: they take on shapes elongated in the direction […]
January 8, 2014
A Piece of Mars: Bright hills appear to be bearded (or perhaps mustached?). What’s going on? Dark sand has blown over some yellow-crested hills and settled on the downwind side, where the hill blocks enough wind that it can no […]
December 23, 2013
A piece of Mars: Normally I post color images, but this one is just too cool to skip. These ripples formed ages ago: long enough ago that the impact of several small bolides formed craters (seen on the left), disrupting […]
December 11, 2013
A piece of Mars: Sand that moves into holes in the ground tends to get stuck there. That’s why this round hole ~150 m across, which was probably once a crater, is now brimming with sand and capped by ripples. […]
November 29, 2013
A Piece of Mars: Two-toned ripples have formed on a steep slope, created by winds rushing downhill (from top to bottom in this frame). The larger ones are big ripples, with peaks more than 30 meters apart. What makes them […]
October 25, 2013
A piece of Mars: Barchan, or crescent dunes, are generally thought to form from winds blowing from a single direction. Reality isn’t usually that nice. Here are two barchans with crescent-shaped slip faces on their eastern (right) sides, indicating that […]
August 8, 2013
A piece of Mars: Creamy dunes (or maybe they’re very large ripples) wind their way northward between mesas. More recently darker, more mobile sand (bluish here) has piled up against the western slopes of the mesas. We don’t know why […]
June 21, 2013
A piece of Mars: Yep, these are dunes shaped into polygons. Each “cell” is about 25 m (~80 ft) across. The crests of these things are outlined in blue, as if somebody traced them with a pen (well it’s stretched […]
June 17, 2013
A piece of Mars: In the lower left of the image, a small hill stands above a plain partly covered by stabilized ripples. Boulders have rolled down the hill as it slowly erodes. If these ripples aren’t ever activated by […]
June 5, 2013
A piece of Mars: Here in the bottom of a crater in Coprates Chasma is the intersection of two sets of ripples: dark, dust-free ripples at the bottom of the crater, and lighter ripples formed from debris that has come […]
May 24, 2013
A piece of Mars: The source of dune sand on Mars is normally something of a mystery. But here on the interior wall of a small crater it appears that small gullies have eroded sediment from the wall and carried […]