Swirls and stripes

A piece of Mars: I know, I keep showing ripples. But they’re all so different. This one has a distinct swirl appearance, like it’s stretched and twisted taffy. The complexities of the winds that create these things are not at all understood. (HiRISE PSP_003101_1320)

Visited wind streaks

A piece of Mars: Back in 2007, the Mars Exploration Rover Opportunity spent a great deal of time investigating the rim of Victoria crater. Here is the northern rim of the crater, showing three dark (bluish) sandy streaks formed by the wind as it blows dark sand out of the crater. You can see small

Complex winds

A piece of Mars: My brain keeps seeing it as stuffed pillows, but it’s the other way around — the sun is coming from the upper left, so the centers of the little polygons are low and their edges are sharp-crested dunes. Or maybe ripples, we’re still not sure. Stare at it until your brain

Tuning forks of the wind.

A piece of Mars: Small, dark ripples have overridden larger, bright ones. The larger ones have some interesting shapes — arcs, splits that resemble tuning forks, and even circles. Their shape is accentuated by the smaller, very regular ripples between them. (HiRISE PSP_004077_1325).

Fashionable stripes of Mars

A piece of Mars: Is it the latest in patterns for ties, or is it Mars? (Can it be both?) These are some unusually regular dunes on Mars, separated by a bouldered surface. The dunes have interesting pale bands common in this region on Mars, as well as an unending supply of long, parallel ripples.

At the edge

A piece of Mars: Old, subdued dunes (in blue) near the south pole on Mars. This shows the edge of a dune field, with white rock-strewn surface beyond the sand. Criss-crossing the sand are the tracks that dust devils have left behind. I wonder if these whirlwinds are the main reason why the dunes are

When dunes die

A piece of Mars: This is what dunes look like when they die. At least on Mars. On Earth they typically get buried or eroded away. On Mars geology works slowly enough that the steep slopes of dunes are gradually reworked and pitted, and covered in fine layers of bright dust. (HiRISE PSP_005980_1085)

Ripples in a crater

A piece of Mars: Many small craters on Mars are filled, at least in part, by small dunes or ripples. It’s one of the distinguishing features of Mars — a surface marked by geology both old (craters) and young (dunes). This particular crater isn’t so old — boulders surrounding it were made from rocks flung

Dust and oddities

A piece of Mars: In the dustier regions of Mars, there are many small dark streaks on steep slopes that we don’t understand well. Because we don’t know much about them we call them “slope streaks”, which is not the most imaginative name. They are actively forming on Mars today, though, and seem to be