NASA’s Mars rover has photographed its first “dust devil”.
A dust devil photographed on Mars by Opportunity. Although common on the red planet, this is the first photograph of such a phenomenon by this NASA rover. The shot’s contrast has been increased in order to make the dust devil easier to see. Credit: NASA/JPL-Caltech/Cornell University/Texas A&M
After more than 6 years on the red planet, Opportunity is still working and continues to move towards its next main objective, the 22km wide crater, Endeavour. However, during the journey, the science continues and the mobile robot is continually taking photographs or performing measurements. This is how it photographed a dust devil on Mars on 15 July. Spirit beats Opportunity hands down! In fact, the phenomenon is a common occurrence on the red planet and the American agency’s other rover, Spirit, has already taken some spectacular shots of these whirlwinds. By assembling the images, the specialists at NASA's Jet Propulsion Laboratory have even obtained a short clip showing a dust devil in action (see below).
It is important to recognise that in hunting dust devils in the field, Spirit beats its twin Opportunity hands down since it has already collected a dozen or so observations! Admittedly, it arrived on Mars 21 days before Opportunity (3 January as opposed to 24 January 2004), but over more than 6 years the gap has proved too small to explain such a difference. Likewise, over such a long period, the chances of taking photographs at the right moment should have balanced out between the two Mars rovers. So, is the region covered by Opportunity less favourable in terms of the occurrence of whirlwinds? Despite appearances, no and the explanation is as follows. Like on Earth, dust devils occur in a dry environment when the ground is hotter than the surrounding air. The air's movement then forms a whirlwind which stirs up the dust on the ground. For NASA scientists, it is precisely this dust that explains why Opportunity has had to wait 6 years before taking its first shot of a dust devil. In fact, Opportunity is crossing a region of Mars (Meridiani Planum) which has less loose dust on the surface than the Gusev crater where Spirit is located. As a result, there are just as many whirlwinds in Opportunity’s region, but simply less loose dust to be stirred up, making the phenomenon more difficult to capture on camera.
Spirit and Opportunity are two identical rovers. This image of one of the two being tested on Earth gives an idea of their size. After more than 6 years spent on the red planet, Opportunity is still operational although Spirit has ceased all transmission, its electronics entering hibernation mode due to the Martian winter raging in the region where it is located. Credit: NASA
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