Lori Fenton's Blog

A piece of Mars: Some of the dunes on Mars are just plain weird. Here are some feather-shaped ones. I’m not sure anybody knows why they form these fractal shapes just yet. I don’t know of anything on Earth that looks like these. (HiRISE ESP_028024_1830 NASA/JPL/University of Arizona)

A piece of Mars: Dark sand has been blown into the scene from the upper right. It has piled up against older, brighter dunes that may now be inactive. The sand drifts on and on, piling up where the wind weakens and carving out rock where the wind is strong. And that is geology on Mars today. (HiRISE ESP_028024_1830 NASA/JPL/University of Arizona)

A piece of Mars: Sandwiched between hills, a huge stepped amphitheater has been carved out of the rock by the wind. The scene is 770×577 m across, with each giant step about 20 m wide. Just imagine a huge concert taking place down in the bottom of this monstrous gap (except the acoustics on Mars aren’t so great). (HiRISE ESP_020534_1825, NASA/JPL/University of Arizona)

A piece of Mars: The dark dune here seems to have a subtle rainbow color across it. Is it a real rainbow? Well, no. Part of it is that I’ve stretched the image to enhance color, so the dark dune should really be more gray than blue. But part of it is real — creamy orange dust has settled in a strip on the left side of the dune, making its contrast with the rest of the dune look like a rainbow. (HiRISE ESP_025001_2255, NASA/JPL/University of Arizona)

A piece of Mars: Most dunes on Mars are the freshest, youngest features around. Not so here. The bright dunes near the bottom here are slowly being buried by debris coming down from the gullies on the slope, coming from the upper left. (HiRISE ESP_029483_1470, NASA/JPL/University of Arizona).

A piece of Mars: These large dunes are located in Kaiser crater, a big crater in the southern midlatitudes. The scene is 789×592 m across. Imagine standing on one of these monsters, and seeing nothing but pristine ripples criscrossing all over the place. (HiRISE ESP_029500_1330, NASA/JPL/University of Arizona)

A piece of Mars: What are those dark, flat circles and why are there little dunes sitting on top of them? They’re probably old impact craters that got filled in with dark sediment, and were then eroded flat. So you’re seeing the old crater floors — the crater rim and ejecta have all been eroded away. Dunes have formed out of some of the dark sediment that’s slowly eroding away. (HiRISE ESP_029422_2055 NASA/JPL/University of Arizona)

A piece of Mars: A lovely little dune is right at the edge of this image, trying its best to migrate into the center of the frame. The bright sickle-shaped part of the dune is its slip face, where sand avalanches down as the wind continually forces the dune to inch forward. The contrast between this bright side and the dark, rippled, windward side, indicates that both bright and dark sand are moving in this scene. (HiRISE ESP_029793_1365, Image credit: NASA/JPL/University of Arizona)

A piece of Mars: Dunes don’t usually have a rough surface texture like these do. It’s not clear what’s going on. Are they ancient dunes that are being eroded? What causes this particular texture? It seems unique to high elevations on Mars. Nobody knows yet. (HiRISE PSP_009448_1670, NASA/JPL/University of Arizona)

A piece of Mars: Dunes often cannibalize each other, with new dunes forming from the sand in older dunes. Here the tan dunes have formed from the sand that made up the grayish blue dunes. Notice the banding on the bluish dunes — this is a sign of erosion. The banding is probably layering in the blue dunes that was exposed as a wind from the northwest scoured the surface. (HiRISE ESP_028918_1605, NASA/JPL/University of Arizona)