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Winter campaign at Cook Haven, Sol 3512 - 3599 (December 13, 2013 - March 10, 2014)
ngunn
post Jan 24 2014, 10:12 PM
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QUOTE (elakdawalla @ Jan 24 2014, 08:12 PM) *
wind more readily lifts sand-sized particles than clay-sized particles, both on Earth and on Mars. It was a mystery until pretty recently how dust was getting lifted off the Martian ground into the atmosphere, when sand didn't seem to move much.


Very interesting. It's obvious there's something amiss with the theory. On Mars the dust is clearly more mobile than the sand or else everything would be grey not red.
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Tycho
post Jan 25 2014, 02:09 AM
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Once lifted in the atmosphere, clay-sized particles stay there for a very long time, mixed up by the wind again and again and spread all over the planet. The sand falls down immediately. Remember there is no rain to wash out the atmosphere.
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algorithm
post Jan 25 2014, 09:04 PM
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Looking at post #86 from mhoward, I noticed a coloured patch on the ground above PI the same as it's 'interior'. Does anyone think there is a link? Maybe this is an impact site where the rock landed (launched by your favourite method) and then rebounded, performing a half sommersault, and then landing in it's present position.
Or am I as mad as a bag of badgers?
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mhoward
post Jan 25 2014, 09:22 PM
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That's the brush mark.
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algorithm
post Jan 25 2014, 09:33 PM
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QUOTE (mhoward @ Jan 25 2014, 09:22 PM) *
That's the brush mark.

You sure?

Strange shaped brush.

Was the inside of the rock brushed as well?
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fredk
post Jan 25 2014, 09:41 PM
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The brush spins, so normally makes a disc-shaped mark. In this case it looks like the plane of the brush was tilted a bit compared to the ground, so only made contact on a portion of the disc (we can see the lower part of the disc).

I think it's pretty unlikely that they'd try to brush a small, loose rock like PI - I doubt the rock would sit still!
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algorithm
post Jan 25 2014, 09:44 PM
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I mention brushing the rock because of the similarity in colour. The reason for my post in the first place.
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ngunn
post Jan 25 2014, 09:51 PM
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Also, being freshly dug up it has no dust on it so it doesn't need brushing.

We have been told that the interior of the rock is chemically unusual but so far nothing about the bright teeth around the perimeter, or have I missed something?
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algorithm
post Jan 25 2014, 10:06 PM
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Because the colour of the inside of the rock is so similar to the 'brush' mark would that indicate that it hasn't been carried that far, or would it put a limit on how far it could have been carried, or an indication of where it may or may not have come from?
And would the place that it came from now be the same colour as the brush mark?
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mhoward
post Jan 25 2014, 10:28 PM
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QUOTE (algorithm @ Jan 25 2014, 03:33 PM) *
You sure?

Strange shaped brush.


Yes, pretty sure in this case: the mark wasn't there in earlier Pancam images before the RAT was placed on that spot. And it looks like a typical glancing brush mark.
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ngunn
post Jan 25 2014, 10:30 PM
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I don't think it has been carried far, just kicked out by a wheel scrunching around in a turn or whatever. Should it match the place where it came from? Yes.
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mhoward
post Jan 25 2014, 10:36 PM
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As for whether the corresponding hole in the ground (assuming it exists) exposes the same colors, I believe Steve Squyres said at the Planetary Radio Live 10th Anniversary Celebration that's something they'd like to find out, and they will be moving the rover soon to try to take a look.
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fredk
post Jan 26 2014, 12:57 AM
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QUOTE (djellison @ Jan 19 2014, 11:00 PM) *
Already done, put to paper, peer reviewed and published
http://www.sciencedirect.com/science/artic...019103513001693

Thanks for the reference. I finally had a look at it, and, judging from Fig 4b, the observed cumulative crater frequency is a bit over 2*10^-6 craters/km^2/year. That's for all craters larger than the smallest observed (roughly 1.5 m diameter). So in 10 years, the odds are about 2*10^-5 that a crater would form within one square km of Oppy.

Even if you follow the trend of the models, which predict higher rates than the observations, the odds are perhaps only 10 times larger (hard to be sure, since the model predictions aren't given for the smallest craters). I guess you should also add meteors small enough that they don't produce craters, but the trend of the cumulative curve (4b) is not promising.

Either way, Oppy would be very very very lucky to experience a meteor hit that close.

On the other hand, the odds are good that Oppy has been within very roughly a 130 km radius of a meteor strike in these 10 years...
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jvandriel
post Jan 26 2014, 10:16 PM
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The Navcam L0 view on Sol 3555.

Jan van Driel

Attached Image
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Phil Stooke
post Jan 26 2014, 11:45 PM
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This is a quick polar version of Jan's new panorama.

Phil

Attached Image


--------------------
... because the Solar System ain't gonna map itself.
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