June 26, 2013

Pale gold satin sand

A piece of Mars: Sand sometimes piles up on steep slopes. It forms downslope streaks as it slides downhill, which here appear like long narrow stripes, like shimmering satin (down is toward the lower left). Note the wind-blown ripples in […]
June 21, 2013

Polygons of dunes

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

Hills, boulders, and wind

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 7, 2013

Blue ribbon

A piece of Mars: In ancient, wind-carved hills, a bluish ribbon of actively moving sand still winds its way. It is a remnant of a long-lived period of wind scour that shaped this landscape. (And it’s been stretched to look […]
June 5, 2013

The colors of geology

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

Where does martian sand come from?

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 […]
May 21, 2013

New dust devils swirls

A piece of Mars: Swirly loops form on the martian surface as dust devils pass by, cleaning up dust on the surface and revealing the dark, rippled dune beneath. Every year the swirls get cleaned off and reform — such […]
May 2, 2013

Dunes on crater bones

A piece of Mars. The dark circle (~170 m across) in the middle of the picture is the interior of what used to be a crater. It’s now almost completely eroded away, probably by the wind. Small dunes have formed […]
April 22, 2013

Topography and the wind

A piece of Mars: Everybody else loves this image because it shows an inverted channel — the remains of a stream that once flowed through this area. But I love it because the little dunes were also formed by a […]