[X] My Assistant

[fredk]

It's been pretty slow in the Spirit forum recently, but hopefully this will reawaken it.

A new thin dark streak is visible in the latest sol 961 rear hazcam, that wasn't visible in the previous shot, from sol 924. It's visible in both L and R hazcam views. It looks remarkably like a dust devil streak, but the scale is very small. Here's the R hazcam from sol 894 subtracted from the 961 image:

The dark streak cuts across more or less from left to right about a third of the frame down from the top. Other differences are visible, mostly around rocks, due to the change in sun angle between the frames.

To demonstrate that the dark streak isn't just an effect due to that change in sun angle, look at these three frames:
sol 856, local time 11:07
sol 961, local time 11:21
sol 894, local time 11:45

You can see that the shadows move progressively from the sol 856 to 961 to 894 frames above, as you'd expect from the local times they were taken. But if you flip between the three frames, you can see the dark streak only in the middle (sol 961) frame. If the streak were due to changing sun angle it would be at least as strongly visible in the 856 or 894 frame. Therefore it's not due to sun angle.

As I said, this is way too small for a dust devil streak. And, I don't think we're anywhere near dust devil season. My guess about the origin of this is a small "crumble event" on one of those dark rocks in the upper left, followed by the normal winds blowing some dark dust downwind.

Anyone know if the streak direction is consistent with what the winds should be doing now? Has anyone else noticed changes near Spirit?