HiRISE images

Ius Chasma dunes: they move
Published 2/20/2018 in Lori Fenton's Blog Author lfenton
Many dunes on Mars are actively migrating, like these dunes (view is 0.4x0.5 km, 0.25x0.31 mi). These are found deep in Ius Chasma, one of the Valles Marineris. These dunes slowly migrate toward the right, pushed by winds blowing from the lower and upper left.       Comparing this recent image with the first HiRISE image taken ~10.5 years ago (that's ~4.4 Mars years) shows development of a crest linking these two dunes, indicating the wind from the upper left has been most active over the last few years. Click on the grayscale image to the left to see an animation of this... read more ❯

Where dune fields begin
Published 2/12/2018 in Lori Fenton's Blog Author lfenton
This is the upwind edge of a dune field (825x625 m, 0.51x0.39 mi). Winds blow down a cliff (offscreen) from the lower right, blowing sand toward the upper left. Elongated dunes have formed parallel to the resultant wind direction, only avalanching into slip faces once enough sand has piled up (there are two slip faces at the upper left). The tan/black mottling shows where tan dust has settled or been removed from the dark sand by recent winds. Large grains are heavier and harder for the wind to move, so they form into ripples (with a 10 m or... read more ❯

Mars' "Type A" wind
Published 2/5/2018 in Lori Fenton's Blog Author lfenton
The busy, busy wind has moved a lot of things to make this 0.6x0.85 km (0.37x0.53 mi) landscape. First it built a big dark dune, covering it and the surrounding surface with ripples. Then it dumped a bunch of bright yellow dust all over everything, maybe the result of a nearby dust storm, or maybe just gradual fallout in a quiet season. And then it made some whirlwinds into dust devils that scribbled away some of the dust, revealing the dark dune surface. (I'll also note that when turned upside down, this looks like an interesting one-shoulder dress with a... read more ❯

Smash! Whoosh...
Published 1/30/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The dark splash pattern in this 0.9x0.9 km (0.56x0.56 mi) scene (click on it for a better view) is the site of an impact crater that appeared between images sometime between August 2006 and March 2010 (Smash!). The main crater is ~7 m (23 ft) across. Impacts smash a little ways into the ground, digging a hole and throwing out stuff that was once buried. Here, the buried stuff is darker than what's right at the surface. There are a lot of other similarly sized craters here, but they no longer have dark ejecta surrounding them.... read more ❯

Arnus Vallis, Mars
Published 1/22/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This is a section of Arnus Vallis (scene is 1.25x1 km, 0.78x0.62 mi). It's a >300 km long valley that was carved out, not by water, but by lava, long ago. Since then the wind has taken over. The left wall of the valley seems to have layers etched into high relief by wind scour; the floor is covered by ripples (TARs, really). But what I love most about this valley is that along the right (east) side, a long dune extends for much of the valley's length (it's why you don't see layers on the... read more ❯

Varying wind directions
Published 1/18/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: This 0.5x0.4 km (0.31x0.25 mi) scene shows two dunes near the north pole. The shape of the dunes indicates two main winds: one blowing left to right (which makes slip faces on the right side, one of which still has some bright white ice on it), and a secondary wind blowing from the lower right to upper left (elongating the upper "corners" of these dunes). The two lee sides are marked by yellow patches, where bright dust falls out of the atmosphere, accumulating in areas of relative calm. But if you look at the boulders (the... read more ❯

Dunes with comet tails
Published 1/8/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The north polar dunes in this 575x325 m (0.36x0.2 mi) scene are made of dark sand covered by bright winter frost (which will soon sublimate away, as this image was taken in late spring). To the right of the dunes extend pale yellow bumpy hills, making the dunes look like they have little "comet tails". What's going on here? These dunes are migrating towards the left, so the tails are what they leave behind. The dunes are located very far north, where the ground is always frozen. Ice freezes the lowest parts of the dunes, so... read more ❯

Fuzzy dunes
Published 1/2/2018 in Lori Fenton's Blog Author lfenton
A Piece of Mars: The dunes (or maybe they're ripples) in this valley appear to be fuzzy (the view is 625x775 m, 0.39x0.48 mi). They're not really fuzzy, but it's not actually clear what's going on. They seem to have smaller ripples superposed on them, and maybe bright dust has settled into the troughs between ripple peaks, so that they take on a striped, feathered look. It's unlike anything I've seen on Earth. (HiRISE ESP_052776_1785, NASA/JPL/Univ. of Arizona) read more ❯

Buried by ejecta
Published 12/26/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: To see this one well you'll have to click on the image. At the lower right, a 240 m (787 ft) diameter crater formed when a bolide hit the surface, throwing out ejecta on the surrounding terrain. Zooming in, you can see that the ejecta has a distinctive rough surface. Farther from the crater there are smooth patches where ejecta didn't fall. What I like about this is the many small bedforms (ripples), some of which are covered by ejecta and some of which aren't. Closer to the crater, you don't see so many of these... read more ❯

The mysterious bright streaks
Published 12/18/2017 in Lori Fenton's Blog Author lfenton
A Piece of Mars: Some things just go unexplained (so far, anyway). Here's a mysterious bright streak (scene is 1.2x1.8 km, 0.75x1.12 mi) concentrated between two sets of ripple-like bedforms. It looks sort of like a river, but it's on flat terrain and it's not water. It's part of a larger set of bright streaks that you can see throughout the top of this broader CTX image (the bright streak shown in detail here is visible as a distinct white stripe on the floor of a crater). My guess is that at some point, probably at least several million years... read more ❯