Let me know if you get tired of these... no, wait. Don't let me know. These pictures from the orbiting HiRISE camera never get old because they're frakking amazing! Here is another awesome avalanche caught in the act... on Mars!
Holy Haleakala! Coooool. Click the pic to nobly embiggen. And oh yes, you want to embiggen this one. This may be my favorite Red Planet avalanche of them all. On the left you can see the surface of Mars: that's frozen carbon dioxide -- dry ice -- covering the ground. The red brick-like pattern to the right of the ice is actually the face of a scarp, a steep cliff. We're looking almost straight down on it, so it's foreshortened, but don't let that fool you; it's 700 meters (2000 feet) high! On the right is the greyish floor, dusty basaltic rock. You can see sand dunes rippling across it, as well as a few boulders here and there. But right there is the plume of a large avalanche, the cloud still rising above the floor! Clearly this was caught within seconds of the landslide hitting the floor of the scarp. The shadow of the plume is clear and obvious below and to the left. That's particularly cool because knowing the Sun angle in the image means the plume height can be determined. They generally rise to 50 or more meters. It's spring in the northern hemisphere of Mars, and the warming temperatures are sublimating the dry ice. This may be causing the slides; the CO2 gets in the cracks of the rocks and dust, and when it goes away the loose debris can be free to fall. The folks at HiRISE have been targeting scarps like this one just in case they can catch avalanches like this. I like this avalanche shot in particular because you can really see the contrast between the layer of ice, the scarp wall, and the floor. It makes for a wonderfully complete scene, and for some reason reminds me of Earth... maybe it's because I live in Boulder, and I'm used to seeing ice covered red rocks with lots of interesting geological bits around. I'm not sure. But like all the other avalanche shots, it reminds me that Mars is a planet, a world, a location, an actual place. It may lack the dynamic and diverse weather we get here on Earth, but there's still plenty going on at that little ball.
Image credit: NASA/JPL/University of Arizona