There was a worrying update posted on the JPL website for Spirit today: an early-season dust storm has darkened its skies enough that its solar panels produced only 89 watt-hours of power yesterday, sol 1,725. Neither rover has ever, ever seen power production levels that low, not even during last year's massive dust storm. In an ominous repetition of the kinds of things that were attempted with Phoenix last week, mission managers are turning off some heaters, like the one that keeps parts of its sensitive Mini-TES instrument from cracking in the cold. Now, they have gone through this drill before, but 89 watt-hours is so small a number that, regardless of the survival strategies used, Spirit will go into a low-power fault status soon if things don't change. "The best chance for survival for Spirit is for us to maintain sequence control of the rover, as opposed to it going into automated fault protection," the update quoted project manager John Callas as saying. Automated fault protection was the status Phoenix was in for its last few sols of life. Looks like they're trying to prevent the same fate from befalling Spirit.
Can Spirit make it? The update goes on to say that "Mars weather forecasts suggest the dust storm may be clearing now or in the next few days. However, the dust falling from the sky onto Spirit's solar array panels also could leave a lingering reduction in the amount of electricity the rover can produce." Spirit's already so dusty -- how much more dust can it handle?
Hold on, Spirit -- please don't let two missions end in one month!
NASA / JPL-Caltech / Cornell
A dusty start to Spirit's winter
This image juxtaposes two "deck pans" captured by the Pancam instrument on Spirit at different times in the mission. On the left is the self-portrait from the top of Husband Hill, when Spirit's deck was nearly as clean as the day the rover landed. On the right is a view taken in October of 2007, following the summer's dust storm. Dust from the sky has settled on both the rover deck and the surrounding landscape, coloring the rover the same rust color as the dirt around it. The dust-covered solar cells cannot be able to generate as much power as when they were clean. Spirit survived the following Martian winter despite the high dust levels, and the rover team got very useful practice surviving through periods of very low power during the height of the dust storm. Now, though, even more dust may be falling on Spirit.