June 3, 2012

Active wind erosion

A piece of Mars: Bright rocks are being scoured and shaped by dark (bluish) sand. On Mars, active geologic activity is easy to identify: when there aren’t many craters visible, you’re probably looking at a surface that is undergoing change. […]
May 31, 2012

Festoons of geology past

A piece of Mars: Erosion by sandblasting has revealed layers in volcanic rock. Likely nearly horizontal, the wind here has shaped the surface so the layers appear to be festoons, swirling across the landscape. (HiRISE ESP_021627_1975)
May 30, 2012

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 […]
May 29, 2012

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 […]
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 […]