They're caused by the spinning motion of rising air as it is heated. The swirling column picks up dust as it moves across the landscape. Mars Pathfinder detected several dust devils during its 83 days of operation on Mars in 1997. Mariner 9 and the Viking landers and orbiters of the 1970s also found evidence that dust devils occur on Mars. Dark streaks and lines on the planet's surface had been puzzling researchers since the spacecraft started orbiting the red planet in 1997.
Dust devils are common in desert areas on Earth, where they last only a few minutes.
That's probably the case on Mars as well, Edgett said. Scientists believe the dust devils are removing some of the bright dust on the planet's surface, causing the dark streak to appear. In recent weeks, Global Surveyor has caught as many as five to 10 at a time on the arid planet, he said. In last week's issue of the journal Science, researchers using elevation and gravity measurements found evidence of a rapid cooling period early in the planet's history as well large buried channels where water once might have flowed. Major differences in the planet's ice caps.