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The Planetary Society Blog
By Emily Lakdawalla
Spirit's cleaning event: The view from space
Mar. 23, 2007 | 13:31 PDT | 20:31 UTC
Last week I wrote about a new tool put together by ESA to allow online viewing the Mars Express HRSC image set called HRSCview. Rover enthusiast Daniel Crotty naturally pointed HRSCview to the Columbia Hills to see what Spirit's landing site looked like from space, and he got this view, which looks pretty familiar. The Columbia Hills are in the center, and you can see a ton of wiggly little dust devil tracks wandering all over the image. This was captured on January 16, 2004, shortly after Spirit landed. Mars Express view of the Columbia Hills (January 16, 2004)Credit: ESA / DLR / FU Berlin (G. Neukum) |
One nifty thing about HRSCview is that when you look at a particular spot, you can easily wander through multiple HRSC images, if they exist, by using a handy dropdown menu at the upper corner of the screen. Daniel noticed that there were a total of three HRSC images covering the Columbia Hills. When he selected one of the alternate views, he was shocked at the change. This photo was captured on October 20, 2005, not quite one Mars year after the first. Those wiggly dust devil tracks are still there, but they're subdued, replaced by a dark swath of wind streaks. You can tell by how the wind streaks tail off of craters that the wind blew from the south-southeast.Mars Express view of the Columbia Hills (October 20, 2005)Credit: ESA / DLR / FU Berlin (G. Neukum) |
So, some time in Spirit's first year at Mars, some event, or series of events, happened; some unusually stiff breeze blew across the area. Intrigued, Daniel checked out the Mars Odyssey THEMIS images of Gusev to see if it recorded the same change. There, too, a change in wind streak direction was visible, but the dates on which the two THEMIS images were taken (September 26, 2003 and October 8, 2005) didn't really improve the constraints on when the event happened by very much. So he dug in to the Mars Global Surveyor MOC data set, and there he struck gold. He found two wide-angle images, from before and after the change in wind streak direction, that were taken only a week apart. The new wind streaks formed some time between March 5 and March 12, 2005. So Daniel has pretty much figured out when the new wind streaks formed. That's pretty cool. But wait, there's more.New wind streaks forming in Gusev craterThis animation flickers between two MOC wide-angle camera images of Gusev Crater, Spirit's landing site. The two images were taken on March 5 and March 12, 2005. In the week between these two images, a prominent new set of wind streaks formed within Gusev crater. Credit: NASA / JPL / MSSS / Daniel Crotty |
Daniel asked himself, did Spirit happen to observe anything interesting happening or changing at its landing site between March 5 and March 12, 2005? He checked out the news and press releases from that time period, and guess what he found?Spirit's cleaning event: before and afterThese two pictures show Spirit's calibration target (the "Marsdial") before and after a cleaning event wiped Spirit's deck and solar arrays clean of the dust that had accumulated during the first 400-plus Mars days of its operations within Gusev crater. The pictures were taken ten days apart, on sol 416 or March 5 (left) and sol 426 or March 15 (right). Data recording the power output of the solar arrays indicates that the cleaning event occurred on sol 420 or March 9. The first dust devils were spotted in Spirit images taken on the next sol. Credit: NASA / JPL / Cornell |
That's right, whatever this wind event was, it seems to be the one that wiped Spirit's solar panels clean and gave the formerly dusty rover a new lease on life. What a cool detective story! This story has been buried in the data that was out there for the public to see all this time, but it wasn't until HRSCview came along that Daniel caught the tail of the tiger and followed it to its head. One thing that Daniel -- and I -- are curious about is why there hasn't been a publication (or at least a conference abstract) on this event. Maybe it's not that surprising to the professionals. But it was surprising to us, and a fun story to track down!
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