08/01/2013 14:48
Volunteers wanted for Mars exploration
Members of the public are being asked to help identify dust features on the surface of Mars.
Volunteers can go to the Planetfour website to see millions of images taken by the Mars Reconnaissance Orbiter (MRO).
The images show some unusual features around the Martian equivalent of the Arctic Circle.
The website gives volunteers a quick tutorial which illustrates some of the likely features of the Martian Arctic.
They are then asked to explore the images and record any unusual activity.
Every winter Mars' polar region is blanketed by a layer of frozen carbon dioxide (dry ice), up to one metre deep. In the springtime, this seasonal polar cap sublimates (changes directly from ice to gas).
"One of the things we found in the MRO images is a really weird set of features that are associated with this process," says Chris Lintott from Oxford University.
Over the winter the seasonal ice layer is transformed to translucent slab ice, which allows sunlight to penetrate to the ground below in the spring. The ground warms up causing the ice to sublimate from the bottom.
This results in gas becoming trapped below the ice layer, under increasing pressure. When a crack or a rupture develops the gas flows out of the opening. The escaping gas carries along loose material, or dust, eroded from the ground. The gas and dust flow up to the top of the ice layer and out into the ambient wind.
The material lands on top of the seasonal ice layer, downwind of the vent, in fan-shaped deposits.