HiRISE images

A piece of Mars: Here are two craters, each of which is ~240 m across. On the right is an old, very eroded crater. It has old, eroded ripples on its floor. The crater on the left is younger, with a mostly intact rim and even ejecta surrounding it. The ripples inside this crater are also younger: more crisp, and less broken-up. (HiRISE ESP_034482_1570, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: On Oct. 15, 2013, Curiosity drove past a crater that has small dunes or ripples on its floor. In a new HiRISE image, you can see Curiosity's tracks from that day (its 424th sol on Mars). While there, the camera took a nice panorama, so I thought I'd show what this crater and ripple field look like both from the rover and from orbit. Note the dark dunes and Mt. Sharp in the background of Curiosity's image. (HiRISE ESP_034572_1755 NASA/JPL/Univ. of Arizona, GigaPan) read more ❯

A piece of Mars: On martian dunes it's all about lines, lines, lines. The prominent wavy ones on the left are thought to be erosional scars left by sliding blocks of dry ice. The little fingerprint-like lines are ripples, like those found on any Earth dune. All those lines tell us that the dunes are formed as the wind, ice, and sand interact over time. (826x620 m, ESP_021838_1300, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: Where the wind blows strong and there's a lot of sand, the surface gets scoured. Some bits of the ground, called yardangs, are more resistant and stick around: they take on shapes elongated in the direction of the wind (in this case, a wind from the lower right). Groups of them are often called "fleets", as they sometimes look like inverted boat hulls. (993x745 m, ESP_034129_1820, NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: Bright hills appear to be bearded (or perhaps mustached?). What's going on? Dark sand has blown over some yellow-crested hills and settled on the downwind side, where the hill blocks enough wind that it can no longer move sand, and it all collects there in rippled drifts. (scene is 386x290 m, ESP_034084_1655, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: A single dune sits on the surface of Mars, not too far from the north pole. It's early spring, but this far north the dune is still covered in white CO2 frost (as well as a thin yellow layer of airfall dust). But the sun has done some work already: the dark spots are areas where enough frost is gone from the warm sun's rays, revealing the lovely black sand beneath. Before long the frost will be gone and the dark dune will be fully released from its wintery blanket. (HiRISE ESP_033729_2565, NASA/JPL/Univ. of Arizona) Update: See... read more ❯

A piece of Mars: Normally I post color images, but this one is just too cool to skip. These ripples formed ages ago: long enough ago that the impact of several small bolides formed craters (seen on the left), disrupting this ripple field (the largest crater is ~85 m across). After the impact, small ripples formed inside the craters, but they never grew to the same size as the original ripples. (HiRISE ESP_033717_1990, NASA/JPL/Univ. of Arizona) read more ❯

A piece of Mars: Sand that moves into holes in the ground tends to get stuck there. That's why this round hole ~150 m across, which was probably once a crater, is now brimming with sand and capped by ripples. (HiRISE ESP_033717_1990, NASA/JPL/Univ. of Arizona) read more ❯

A Piece of Mars: Two-toned ripples have formed on a steep slope, created by winds rushing downhill (from top to bottom in this frame). The larger ones are big ripples, with peaks more than 30 meters apart. What makes them unusual, however, is stark contrast between the dark (bluish) upwind side and the light (pale tan) downwind side. How did that happen? It's because sand blowing downhill preferentially scours the dark upwind side of the ripples, leaving the downwind side untouched. (PSP_002208_1755, NASA/JPL/University of Arizona) read more ❯

A Piece of Mars: These rocks look like hooded figures from some dark fantasy story. European standing stones should be jealous, they don't typically get a shroud of dark sand to add to their mystery and etch them into beguiling shapes (but then perhaps they don't need it). Here, sand moving from the upper right to lower left slowly carves out these lovely shapes. (PSP_007535_1755, NASA/JPL/Univ. of Arizona) read more ❯