Dusty rejuvenation.

The Mars rover Spirit just got a windblown reprieve. In January 2004, the rover landed in a dusty crater. Ever since, its solar arrays--its main power source--have been getting dirtier and thus less efficient, limiting Spirit's performance. For instance, the robot typically drove for fewer hours each day or took in less data than its cleaner twin rover Opportunity did.

When Spirit landed, it could generate 900 watt-hours of energy, but its solar-array output has since dropped to less than half that amount. As recently as March 9, "the solar arrays [were] just filthy," notes chief rover scientist Steve Squyres of Cornell University.

Then, good news blew in. Literally overnight, between March 9 and 10, dust somehow left Spirit's arrays. Energy generation jumped from 400 to 800 watt-hours.

Rover researchers say that they probably owe thanks to dust devils, whirls of warm air and dust that are common on Mars and could have swept clean Spirit's arrays. Indeed, a day after the change, Spirit's cameras for the first time snapped images of two dust devils in action.

Despite the energy boost, Spirit is by no means a new vehicle. "It could drop dead on us anytime, so we're going to continue to push the vehicle very, very hard," notes Squyres.--R.C.