Live Dust Devil? |
Live Dust Devil? |
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#101
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Rover Driver ![]() ![]() ![]() Group: Members Posts: 109 Joined: 2-May 04 From: Litchfield Park, Arizona (Phoenix area) Member No.: 71 ![]() |
Man, this looks an awful lot like a dust devil in the distance. What do you think?
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#102
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![]() Martian Photographer ![]() ![]() ![]() Group: Members Posts: 352 Joined: 3-March 05 Member No.: 183 ![]() |
QUOTE (Opie @ Mar 14 2005, 04:54 AM) Yeah, I'm starting to think that the real oddity is the fact that dust devils haven't been spotted before. I suspect that there is at most a 1 to 2 hour window during the day when devils form--and that we are entering the dust devil season. My guess is that it won't take long for the clever folks at JPL to pin down the optimal time of day for devil formation and capture some semblence of a movie. This THEMIS image was posted previously in this thread. Looking at it, you've got to believe a devil passing within Spirit's field of view is a very common occurence. The tricky variable in capturing a devil with the camera is their ground speed. If they move quickly (horizontal wind velocites on Mars can be rather high), that would explain the dearth of images thus far. http://themis-data.asu.edu/img/V07909002.html The dust devil window is probably longer, maybe 1100 to 1500. During about that interval, Pathfinder imaged about a dozen dust devils in one or two sols. Several dust devils were tracked moving between images. At a few to a few 10s of m per sec, single exposures of them aren't inhibited by velocity; repeat exposures of distant (>1 km) ones are reasonable to expect, especially up/down wind. For MER, the big difference between now and landing is we're on a hill. From the plains, you see dust against dust, and they're harder to see (not impossible, based on Pathfinder). From the hill, we're seeing light dust against a darker surface. So, there were (must have been ...) dust devils early in Spirit's mission; then none through winter; now they're kicking back up, but easier to find. |
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