Winter campaign at Cook Haven, Sol 3512 - 3599 (December 13, 2013 - March 10, 2014) |
Winter campaign at Cook Haven, Sol 3512 - 3599 (December 13, 2013 - March 10, 2014) |
Dec 13 2013, 04:31 AM
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#1
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Senior Member Group: Moderator Posts: 3431 Joined: 11-August 04 From: USA Member No.: 98 |
She's there! Opportunity drove down to the "Cook Haven" bright outcrops on Sol 3512.
Even better, news via Twitter that currents on the front right wheel are back to normal. Phew. |
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Jan 19 2014, 05:33 PM
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#2
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
Of course RF doesn't steer, but that still leaves three steering wheels. Walfy's idea actually sounds like the second good idea we've heard (after the obvious rock-popped-out-while-being-driven-over).
The basic problem is that Pinnacle Island moved a considerable distance, as the debris on its rover side indicates. The slopes here are fairly subtle, around 15 degrees. In Mars gravity, that seems to be too shallow for a rock shaped like PI to roll easily. So PI must have been given a kick somehow. Getting squeezed under a wheel, and now Walfy's idea are the only ideas that seem to work. (The wheel rotation speeds are so slow that I can't believe PI being trapped inside a wheel and then spat out. And the odds of a meteor strike nearby have to be incredibly small.) |
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Jan 19 2014, 06:17 PM
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#3
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
Walfy's idea actually sounds like the second good idea we've heard The turning of a steering actuator flicking a rock across the ground? Have you seen how slow the wheels steer? It's incredibly slow. Sorry - I don't buy it. Moreoever - how would a steering actuator throw a rock infront of the rover? Walfy's animation shows it being throw away from the rover....not right infront of it. I don't know if it's ejecta...it does inherently seem unlikely - but it's not that far beyond the realm of possibility. The modern day cratering rate as derived from orbital discoveries is such that I believe it was characterized thus : Within the duration of one crewed surface mission of a martian year - statistically there would be a new impact crater formed within earshot. We've been here 5 martian years. It's far far from impossible that it could be a piece of ejecta. It could be a tiddlywink's like pinging of a rock from under a wheel. But a steering actuator didn't just flick a wheel several meters....I don't buy it. |
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Jan 19 2014, 08:10 PM
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#4
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
The turning of a steering actuator flicking a rock across the ground? Exactly. As Walfy's animation shows, the idea is not that the slow movement of the wheel while steering acted like a golf club or putter to shoot the rock out. Of course that could not happen. The idea is that the rock was stuck in place, which would not be surprizing. As the steering wheels turn against the rock, the force builds until the rock's connection to the ground snaps. Suddenly it's free and you'd expect it to move out faster than the speed of the steering wheels. And there would have been two steering steps, at the start and end of the turn - is it clear that neither could've snapped the rock out in the right direction? Perhaps it ricocheted off another wheel? About ejecta, we need actual numbers to say anything definite about how likely a nearby hit is. But this is what makes me extremely sceptical: We've seen several meteors within pancam-shot of Oppy, but no evidence of recent hits (last 10 years, say) of meteors or ejecta. So what are the odds that when we do see a fresh piece of ejecta, it hit within a couple of metres of Oppy? Surely it would've been far more likely to hit a few years ago, say, and then we drove up to it. It's the close link with Oppy and the timing that strongly suggests a connection with the bump on 3540. |
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