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Emily LakdawallaJune 27, 2008

Strange things under Phoenix

I've received two questions very frequently from readers: "Have they taken another look at Holy Cow yet to see if it's changed?" and "What were those splotches on the leg of the lander in the first image of Holy Cow?" Well, I can now tell you that the answer to the first question is "yes" -- they re-imaged Holy Cow yesterday, sol 31. And there's no official statement from the team yet, but I've looked at the photos and if there is any change, it's very subtle, and impossible to prove from the raw images that are available from the mission website. The team has better data, of course, and may be able to see subtle differences that I can't; but with what I have in front of me I don't see any differences between the two images that can't be explained away as differing shadows, compression artifacts, or a result of a slightly different position of the robotic arm for the two images.

Holy Cow on sol 8 and sol 31

NASA / JPL / UA / MPI / animation by Emily Lakdawalla

Holy Cow on sol 8 and sol 31
This animation flickers between two images of Holy Cow taken on sol 8 and sol 31 of Phoenix' mission to Mars using its Robotic Arm Camera. Some changes between the two images are a result of the different times of day that they were taken (the set from sol 8 was taken at 15:00 local solar time, the set from sol 31 was taken at 14:39) and also from a slightly different position for the robotic arm. If there have been any changes to the ice at Holy Cow between sols 8 and 31, they are subtle enough to be difficult to observe in these two images.
However, there's something very strange happening at the edge of the photo. One of the lander legs was visibly covered with a bunch of splotches in those first pictures from sol 8. When people asked me what they were, I said it must just be dust kicked up from the landing; given what we know about how fluffy and clumpy the soil is at the Phoenix landing site, it seems perfectly reasonable that clumps of dust blasted off the surface by landing jets should stick to the legs. Fine. But why are there more clumps on sol 31 than there were on sol 8?
Phoenix lander leg on sol 8 and 31

NASA / JPL / UA / MPI / animation by Emily Lakdawalla

Phoenix lander leg on sol 8 and 31
Eight sols after landing, Phoenix used its robotic arm camera to photograph the legs that support the lander. One of the lander legs was observed to be covered with bright splotches after landing. On sol 31, the image was repeated in order to look at the ice patches called Holy Cow. The splotchy lander leg had more splotches on sol 31 than it did on sol 8.
Being fanciful for a second, it looks like Phoenix' leg is getting moldy! Since it's bright, I suppose it could be that frost is depositing on the permanently shadowed, probably pretty cold surfaces of this lander leg. I guess. But I'm not convinced -- we don't see the same splotchy coating on the other leg in the foreground. So I'm afraid to say I don't know what the heck we're looking at here, but it's weird! raw images web page is updated to sol 31.

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
Read more articles by Emily Lakdawalla

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