dunes

June 20, 2012

Dune bones

A piece of Mars: The thin stripes within stripes are the bones of dunes. You’re seeing old dunes that have had their tops eroded away so you’re seeing into their insides, as if you were dissecting them in a biology […]
June 19, 2012

The edge of the ice

A piece of Mars: This is the edge of the northern polar cap on Mars. At the top is the bright icy surface, which is abruptly cut by a cliff. The wall of the cliff shows many layers of different […]
June 6, 2012

Stretched out

A piece of Mars: Dunes near the north pole take on a stretched appearance. It’s been proposed that ice in the dunes acts to cement them, which makes them look elongated. (HiRISE PSP_010219_2785)
May 28, 2012

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 […]
May 27, 2012

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 […]
May 24, 2012

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 […]
May 23, 2012

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 […]
May 22, 2012

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 […]
May 13, 2012

One perfect barchan on Mars

A piece of Mars: In nature most dunes pile on one another or strongly influence each other. But occasionally, like a perfect flower or crystal, you find a perfectly shaped dune. Here is a crescentic dune, called a “barchan”, formed […]