Spirit, the Mars rover, has snapped pictures of two dust devils swirling over the surface of the red planet. One was even was captured by both of the rover's cameras, allowing the mission scientists to calculate its speed and direction. This is the first time dust devils have been seen on Mars since the 1997 Pathfinder mission.
Another mini whirlwind seems to have passed directly over the rover, clearing accumulated dust from its solar panels: shortly after the picture were taken the rover's solar panel power output returned to 93 per cent of its original levels.
However, scientific opinion is divided about the cause of the cleaning, New Scientist reports. The exact time of the increase in power output is still being calculated, and Geoffrey Landis, a member of the science team, told the publication that the clearing could have taken place at night. Since the dust devils only occur in the midday sun, that would mean a strong breeze could have been responsible.
But a scientist at NASA's Jet Propulsion Laboratory, Matthew Golombek, who also worked on the Pathfinder mission, says that this is implausible. "We wait for months to see a dust devil and finally catch one and there's this big power boost within a day of it? That's too much of a coincidence," he told the magazine.
One alternative scenario, of course is that the rover stopped, just for a moment at a red traffic light and a Martian with a squeegee gave it a quick clean, in accordance with that particular universal law. It is not known whether NASA plans to equip future missions with loose change to prevent angering the natives with poor tipping.
The images have given scientists a way of measuring windspeed on the surface of the red planet. Neither rover carries an anemometer. Landis said that if more devils were spotted, the researchers could even begin to draw some conclusions about their duration and frequency. He added that the snaps were the highlight of the mission in terms of atmospheric science. ®