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 class and looking at their skeletons. That’s unusual — on Earth dunes usually get buried

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 materials — the darker ones are old dunes. How cool is it to know that

Generations of erosion

A piece of Mars: Sometime in the past, large ripples wandered the dusty lanes of this landscape, sandblasting the hills as they marched on by. Those ripples stopped moving and turned into the fossils you see here. Their bumpy texture indicates that they too are slowly being eroded away. (HiRISE ESP_026462_1740)

Enigma

A piece of Mars: Here is an example of an aeolian enigma. Dunes are depositional, meaning they are made of stuff that piles up on a surface. But these dunes show the strata of the underlying rock within them, which means these things were made from erosion of this rock. So we don’t really know

Boulder tracks

A piece of Mars: You can’t easily tell here, but you’re looking at a steep slope that is high at the bottom of the image and flattens out at the top of the image (the small dunes at the top sit at the foot of the wall). What’s neat here are the many small boulder

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. This is a good example of such a surface. (HiRISE ESP_016000_1670)