Spirit gets brushed off

There was great news last night from Mars Exploration Rover mission operations: Spirit seems to have enjoyed another "cleaning event." Cleaning events are what's kept the rovers alive for so much longer than their design lifetime. The rovers have no technology to clean off their solar panels, so it was assumed that their lives would be ended when dust deposited on the panels to such an extent that the panels' ability to generate power was compromised. But puffs of wind have, from time to time, dusted off the panels, producing a jump in power and giving both rovers new leases on life.

Spirit had been getting very dusty and -- as of A. J. S. Rayl's last rover update -- was down to approximately 450 watt-hours, despite the fact that it's nearly receiving its maximum amount of insolation. (Mars' southern summer solstice is only a couple of weeks away, coming up on July 4.) Spirit needs roughly 300 watt-hours for housekeeping; power above that is available for more fun stuff like driving, operating the arm, and capturing science data. So it's great news to read that the cleaning event has boosted Spirit to more than 600 watt-hours. Opportunity, by contrast, has been getting lots of help from wind lately, and is riding high at (at last update) 850 watt-hours.