Latest Posts

Summery dune

ESP_035997_2565_0.38xA piece of Mars: Last December I blogged about a picture of a sand dune taken in early northern spring. This is the same dune, without frost, now that summer has come to the northern hemisphere and all the frost is gone. It’s quite a difference. Apparently the dunes are controlled by ice in the winter and by the wind in the summer. (HiRISE ESP_035997_2565, NASA/JPL/Univ. of Arizona)

How hills change dunes

ESP_036934_1915_0.38xA piece of Mars: Using dunes to interpret the winds can be a tricky business. Here’s one reason why: most of the dunes here go from the upper left to lower right. But the ones inside the funky oblong crater go from the upper right to the lower left. Why? One of two reasons. Either the rim of the crater rotates the winds that blow inside, or the rim blocks one wind but lets in another that is less effective at making dunes outside. (HiRISE ESP_036934_1915, NASA/JPL/Univ. of Arizona)

Where is Curiosity on her 1 Mars year anniversary?

ESP_029034_1750_1.0x_MSLA piece of Mars: Curiosity has been trolling around on Mars for one martian year, so I think it’s time I posted an update on where it is and what it’s seeing. Right now (late June 2014), the rover is rolling across meter-sized ripples, heading south toward Mt. Sharp. In the near future there will be even more impressive ripples, and then finally the terrain will start to grow more interesting. I will post more of these in the months to come. (HiRISE ESP_029034_1750, NASA/JPL/Univ. of Arizona)

In the lee

ESP_034084_1655_1.0xA piece of Mars: This crater (290 m or 950 ft across) is crawling with all sorts of ripples and dunes. The wind mainly blows from the top to the bottom of the frame, and it is responsible for the wonderful textures in the dark gray sand. It has also formed larger, cream-colored ripples. The creamy and dark gray sand have taken turns burying one another, like vines competing for sunlight. (HiRISE ESP_034084_1655 , NASA/JPL/Univ. of Arizona)

Swirly rocks

ESP_036436_2645_1.0A piece of Mars: Never mind the 4 m (13 ft) boulders that have fallen downslope, or the rippled sandy surfaces here. Look at those bright swirls in the ground. Those are the former interiors of sand dunes, which were trapped and incorporated into the bedrock (like dinosaur bones, but without so much rawr). The wind has been blowing sand around on Mars for a long, long time. (HiRISE ESP_036436_2645, NASA/JPL/Univ. of Arizona)

Whither the wind

ESP_036393_2560_1.0xA piece of Mars: Which way did the wind blow here? You can tell by looking at the dune and its ripples. The slip face (the avalanching slope of the dune) faces downwind, so the strongest wind here mainly blows toward the upper left. But that’s not the whole story, because, like on Earth, martian winds are always shifting. Recent avalanching and some ripples on the slip face show that the most recent wind blew toward the top of the frame. The dune is 267×110 m (876×361 ft). (HiRISE ESP_036393_2650, NASA/JPL/Univ. of Arizona)

The always-changing landscape

ESP_035558_1830_0.831xA piece of Mars: Over time, windblown sand can wear down a surface. This isn’t so common on Earth, where water, ice, and life are more likely to change the landscape, but it’s typical of many places on Mars. Here, we see one moment in time, where neverending sand (blowing from bottom right to top left) creates a pattern on the surface and scours a hole around a resistant rock. (ESP_035558_1830, NASA/JPL/Univ. of Arizona)

Flow

ESP_031944_1790_0.38xA piece of Mars: This is a bit of the flank of Arsia Mons, one of Mars’ great volcanoes. The big changes in topography are ancient relics of erosion by lava and great tectonic pulling. What I like is that the scene (1.58×1.18 km, or 0.98×0.74 mi) is covered in bright dust (looks a bit like snow here, doesn’t it?). And that dust has been eroded by wind channeled through the topography. So here we see signs of flow, both from ancient lava and from more recent wind. (HiRISE ESP_031944_1790, NASA/JPL/Univ. of Arizona)

Debunking Hoagland’s “Glass Worms” with HiRISE

ESP_035634_2160_1.0xA 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)

How we know wind blows down Olympus Mons’ flanks

ESP_035663_1985_1.0xA piece of Mars: It’s similar to my last post, but I love these wind tails. This is a tiny bit of the eastern slope of the gigantic volcano, Olympus Mons. The dusty surface has been covered by boulders (the largest of which is ~20 m, or 65 ft), probably flung there from a distant meteor impact on Mars. Winds screaming from the top of the volcano (from the left) have formed wind tails in the lee of these boulders. And there are some funky little ripples on them. (ESP_035663_1985, NASA/JPL/Univ. of Arizona)