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 21, 2012


A piece of Mars: Sedimentary layers on Mars are revealed by sandblasting. These are giant staircases dropping down towards the upper right, looking like some old eroded temple or city. Some bluish sand remains as a reminder of what scoured […]
May 20, 2012

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). […]
May 17, 2012

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 […]
May 16, 2012

Wind and hills

A piece of Mars: Blueish and yellowish ripples wind their way around a bright hill. The yellowish ones are probably not moving anymore, but the blueish ones are likely still active from time to time. (HiRISE ESP_020889_1320)
May 14, 2012

Swirls like ribbon ice cream

A piece of Mars: When the wind erodes layered rocks, it can create a dramatic swirly pattern like this. It looks like ribbon ice cream to me. Mmm, rocks. (HiRISE ESP_011582_1730)
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 […]
May 10, 2012

So beautiful

A piece of Mars: The dunes can be so beautiful on Mars. What a lovely vacation spot this would be, provided you brought a large supply of oxygen, food, and a heat source to keep you warm. (HiRISE ESP_026416_1620)