12-mile-high dust devil photographed on Mars
The Buzz: Hot on their trail
Such a phenomenon -- 12 miles high in fact -- was photographed last month on an area of the Martian surface known as Amazonis Planitia. A photo of the dust devil was released this week by scientists at the Jet Propulsion Laboratory in La Canada Flintridge, Calif.
"It really is the size of it that is the unique thing," said Ashwin Vasavada, a JPL research scientist. "Conditions allowed this single giant vortex to form and survive to suck up dust all the way to that height."
The sun beats down on the desert-like surface of Mars and -- thanks to the lack of water and the "extremely thin atmosphere" there -- convection begins, he said. "Roiling, turbulent air" forms at the planet's surface in a layer five to 10 miles thick, he added.
These types of conditions can send dust devils spinning, said Vasavada, who is also a deputy project scientist for the Mars Science Laboratory, the rover nicknamed Curiosity that is now on its way to the Red Planet.
Arguably as impressive as the natural phenomenon is the technology that allowed it to be photographed for us to see back on Earth.
The $720 million Mars Reconnaissance Orbiter has been mapping Mars since March 2006. It has a camera "the size of a big telescope" that allows scientists to see details on the surface of the planet that are only 12 inches across, Vasavada said. From orbit, the camera can see the golf-cart-size rovers Spirit and Opportunity, even picking out their tracks.
The camera was used to help scientists pinpoint the spot where Curiosity will land when it reaches Mars in early August. The $1.8 billion rover was designed to look for evidence that the planet could have harbored life in a warmer, wetter past.
Curiosity will land at Gale Crater, where a mound exists that Vasavada likened to "a book that has chapters from all the major parts of Mars history." Scientists are especially interested in clay rocks called phyllosilicates that could only have formed, they think, in a climate that would have been hospitable to living beings.
Elsewhere in the mound are sulfates that formed when Mars was drying out. The most recent history, Vasavada said, is "characterized by a lot of boring dust."
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