A Piece of Mars: This 480x270 m (0.3x0.17 mi) scene shows the contact between two very different terrains. On the left is a bright surface with polygonal cracks (characteristic of periglacial terrain - this is at a high latitude). On the right is a dark rippled sand sheet that superposes the polygonally-cracked surface. The long meandering furrows might be the beginnings of polygonal cracking in the sand, which might expand if wind doesn't erase them. (HiRISE PSP_006473_1125, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: Several years ago, a guy named Richard Hoagland claimed that some parallel linear features on Mars looked like the ridges of a transparent earthworm, calling these things "glass worms". Phil Plait debunked it nicely, but Hoagland stood his ground. He hasn't said much about them lately, has he? Here's why. New images show that, as scientists originally thought, these are nothing more than windblown ripples in the floors of channels, just like the many thousands of ripples seen all over Mars. Go science! (HiRISE ESP_035634_2160, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: I just adore that the wind can do this to a landscape. Over a long period of time, two different winds have scratched deep grooves in a rocky surface. Wind-carved rocks like this are called "yardangs". We have them in some deserts on Earth, too, but I've never seen two overlapping directions like this on Earth. Why are they more prominent on Mars? Mars has no oceans, no rivers, no beaches, no snowfall and no rain to change the surface, so the wind plays a stronger role in shaping the landscape. (HiRISE ESP_028200_1810) read more ❯

A piece of Mars: Steep slopes in some parts of Mars are prone to very thin landslides that leave behind dark tracks. The landslides may be triggered by the wind or nearby impacts. They always move downslope -- in this case from upper left to lower right, meandering around craters and lapping up against old, stabilized dunes. The darkest one here is brand new, having formed sometime between 2007 and 2012. (HiRISE ESP_028642_1800) read more ❯

A piece of Gale crater, Mars: Here is a tiny piece of feathery terrain way up high on Mt. Sharp, the mountain that Curiosity will one day climb. This is a special unit of fine-grained material that has weathered into a distinct feather shape by winds from the northeast. At high resolution, grooves carved by this wind are still visible, and blueish sand indicates that this erosive process is likely still active. (HiRISE ESP_028335_1755) read more ❯

A piece of Gale crater, Mars: Here are some of the large, dark dunes not far from where Curiosity has landed. They're pretty big monsters, 200-300 meters across. Their shape indicates they've been formed from two different wind directions: one blowing from the north and one from the ENE. These are the winds that Curiosity will experience on its trek to Mt. Sharp. (HiRISE ESP_018854_1755) read more ❯

A piece of Gale crater, Mars (Aug 11, 2012): This is a tiny portion of the ancient river channel that Curiosity will use to climb up Mt. Sharp in the coming year. It's a fascinating place, full of pale fractured rocks and partially buried by bluish-gray sand and ripples. (HiRISE ESP_025935_1750) read more ❯

A piece of Gale crater, Mars: These are rocks on Mount Sharp, where the Curiosity rover will be headed in the coming months. Like many of the surfaces in Gale crater, these have been streamlined by sandblasting over the eons. (HiRISE PSP_009861_1755) read more ❯

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 up. As usual, it's in the lee of a topographic feature. (HiRISE ESP_027002_1765) read more ❯

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 it a type of dune called a barchan. The other dunes are called "dome dunes", because they don't have proper slip faces. It is arguable that they aren't really proper dunes at all. (HiRISE ESP_027378_2540) read more ❯