It looks like someone has been painting blue streaks on the wall of this Martian crater (see image, right). But in fact this is a false colour picture from the High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA's Mars reconnaissance orbiter, showing areas recently disturbed by an avalanche.
The crater, called Zunil, is 10 kilometres wide and lies just north of Mars's equator. The ubiquitous reddish dust that coats much of the Martian surface is absent from the areas where the avalanche passed, indicating that the disturbance is recent.
The avalanche might have been triggered by a Marsquake, or the impact of a small meteorite, suggest members of the science team on the HiRISE website.
There also are signs that a much bigger but more ancient landslide occurred on the slopes of Mars's Olympus Mons, the largest volcano in the solar system. Another image captured by HiRISE shows part of a halo of material around the volcano.
The halo occupies most of the image, but ends at the upper left. This boundary may have been created when boulders, flowing en masse, moved up a slope and then receded like a wave on a beach.
"When there's that much rock flowing like that, it does things like water does," says Laszlo Keszthelyi, a scientist with the HiRISE team based in Flagstaff, Arizona, US.
This behaviour is similar to the way dry sand can be poured like a liquid even though it is made up of solid particles. But in the proposed landslide scenario for the halo, "huge boulders and house-size rocks were moving around," says Keszthelyi.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
