[X] My Assistant

[Burmese]

More *yawn* dust devils (2)

http://marsrovers.jpl.nasa.gov/gallery/all...56P0660L0M1.JPG

Spirit would be hard pressed, I think, to make it through a day of navcam/pancam shots of the plains and -not- catch a dust devil in the act.

[Cugel]

Is it my imagination or are these DDs getting bigger and more frequent over the last few weeks? I mean, right now Spirit cannot point its camera anywhere anytime without capturing at least 1 or 2 of these things at least. And they are huge! My worry is that we are seeing the prelude to what could be a local duststorm. Or is that nonsense?

[Marcel]

Is it my imagination or are these DDs getting bigger and more frequent over the last few weeks? I mean, right now Spirit cannot point its camera anywhere anytime without capturing at least 1 or 2 of these things at least. And they are huge! My worry is that we are seeing the prelude to what could be a local duststorm. Or is that nonsense?

I think you're right about the DD's. Frequence (and size !) increased dramatically. I don't know however if this indicates that a duststorm is coming up. I might be two completely different mechanisms (dust storms are a global happening, while DD's are induced on a regional scale due to heating of the lower atmosphere by a sun warmed surface). Secondly, i don't know if we have to be worried about a dust storm at all. I have this feeling that even if a dust storm is severe, there's still enough energy left to keep the rover awake. About the DD's: It might even be a positive development: the more DD's, the more cleaning events......

[slinted]

Secondly, i don't know if we have to be worried about a dust storm at all. I have this feeling that even if a dust storm is severe, there's still enough energy left to keep the rover awake.

I can't see any way around a strong global dust storm as like what was seen in 2001 being debilitating to either rover at this point. Even with Spirit's peak power through the roof at the moment, we'd be talking about multiple months of elevation tau values way beyond anything that has been seen so far in the mission. The Mars Climate Database lists a moderate global dust storm as tau ~ 2.0, and a severe one as 5.0. At 5.0, the ground would receive less than 1% of the potential direct sunlight (indirect would become much more important, but not enough to make up that big a difference), temperatures on the surface would plummet requiring more energy for heating up the rover, etc. I don't mean to be a doomsayer, but this would be the kind of large unforeseeable problem that could end the mission.