HiRISE images

A Piece of Mars: Hargrave crater has an amazing array of colorful surfaces, each of which reflects a different type of rock (this scene is 480x270 m or 0.3x0.17 mi). I like the ripples sitting on top of it all; I've long thought that much of the material in those ripples hasn't moved very far from where it originated. Here's a good example of why. The ripples on the greenish surface have incorporated some local greenish material. The same is true of the tan ripples in the lower left. I'd bet most of this stuff has only moved as far... read more ❯

A Piece of Mars: This 738 x 415 m (0.46 x 0.26 mi) scene shows dark sand flowing down a channel bisected by a ~60 m (~200 ft) tall, thin "island". That island, and many others around it (see the whole image), is what remains after windblown sand slowly carved away the rest of the rock, the same way rivers slowly cut through rock on Earth. The presence of the dark sand shows that the process is still active today. (HiRISE ESP_04400_1750, NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: The gray area in the center of the 480x270 m (0.3x0.17 mi) area is an erosional remnant: once, more of this area was covered by the gray stuff, but some of it has eroded away (most likely by the wind) to reveal the underlying terrain below. The wind probably blew from upper left to lower right, lifting away the finer grains and leaving behind the larger, heavier ones. Some of the larger grains have formed into ripples, that in some places may be the only sign that the overlying layer was ever there. (HiRISE ESP_043136_2020, NASA/JPL/Univ.... read more ❯

A Piece of Mars: This 480x270 m (0.3x0.17 mi) scene shows a dark dune peeking out from under its cover of winter frost. In this picture it's late spring, but still cold up at this latitude - it's as far north here as the Greenland town of Qaanaaq (pop. 656 as of 2013). The CO2 frost here lingers on shady slopes until summer, preventing the dunes from migrating until it's gone. (HiRISE ESP_043799_2570 NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: The long meandering lines snaking across the image (3.2x1.8 km or 2x1.1 mi across) are inverted channels. They are river deposits that once were the lowest part of the landscape (rivers always are), but then the water dried up and wind erosion took over. The river channels were more resistant to erosion and so now they stand above the rest of the terrain. The wind left behind straight, streamlined hills called yardangs. Given enough time, the wind will scrape at the surface until both the yardangs and the river channels are gone, but for now there's... read more ❯

A piece of Mars: This 480x270 m (0.3x0.17 mi) area is a steep slope that plunges down to the upper left. A pile of dark sand, covered by brighter tan dust, clings to the hillside. Usually the martian wind blows sand into ripples, and you can see where it's tried to do that here. But the steep slope triggers thin dark avalanches of dark sand that compete with the wind in shaping the sandy surface. (HiRISE ESP_043085_1670 NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: This 0.96x0.54 km (0.6x0.33 mi) area shows ripples forming on a layer of dark gray material. In a few spots, the gray layer has been eroded away (probably by wind scour), revealing the lighter, tan-colored terrain below. Geologists call these exposures windows, because you can see through one layer to another that's underneath. (HiRISE ESP_043086_1715 JPL/NASA/Univ. of Arizona) read more ❯

A Piece of Mars: This 480x270 m (1575x886 ft) area shows a seemingly endless field of ripples. They're big, about 50 m (164 ft) from crest to crest, and probably about 5 m (16 ft) high. Is there a knit or crochet pattern out there that looks like this? You could market it to some Mars aeolian scientists... (HiRISE ESP_042360_1755, NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: Most of the scene (0.96x0.54 km or 0.6x0.34 mi) is one long slope of a dune. The crest is the line in the top right; the ground below is in the bottom left. If you ever walk along a dune or beach, you'll see small ripples that can reach up to about a meter in length. But the ripples on this dune extend from the crest to the ground - they're more than half a kilometer (more than a third of a mile) long! (HiRISE ESP_043098_1650 NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: This 3.2x1.8 km (2x1.1 mi) area shows terrain covered by bright dust. Dark stripes are areas where wind has lightly scoured the surface, revealing the dark material beneath. Faint bright lines criss-cross the surface - these are tracks left by dust devils. The dust devils disturb the surface but don't lift up enough dust to reveal the darker surface underneath. (HiRISE ESP_042691_2060, NASA/JPL/Univ. of Arizona) read more ❯