July 16, 2012

Patch of blue

A piece of Mars: Most of the image, stretching beyond the edges of this frame, shows a bland gray landscape of lava blanketed in dust. But one small patch of blue shows where sand is still actively moving and piling […]
July 14, 2012

Barely a dune

A piece of Mars: What makes a dune different from a random pile of sand? Usually the requirement is that it has a “slipface”, a steep avalanching slope. The central dune in the image here has a small one, making […]
July 11, 2012

Wrapping around

A piece of Mars: Dunes near the north pole of Mars form in a very cold environment. Winter ice continually tries to stop them in their tracks, which makes for unusually rounded dunes like these. (HiRISE ESP_027451_2635)
July 10, 2012

An intriguing mess

A piece of Mars: What an intriguing mess this is. These are dunes or ripples, oriented every which way, and mottled with white spots. The different orientations tell us that the winds blow from several different directions, on timescales long […]
July 9, 2012

Dunes all gone

A piece of Mars: Way up in the cold northern plains of Mars, some of the dunes are being blown away slowly by the wind. Here are some that are barely there yet — dark patches of sand in the […]
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 18, 2012

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 […]
June 17, 2012

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 […]