Geomorphology of Gale Crater, Rock on! |
Geomorphology of Gale Crater, Rock on! |
Sep 26 2012, 10:22 PM
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
I'd like a discussion thread about the geology detatched from the time limits of current MSL threads. We had a 'Geomorphology of Cape York' thread that attracted a lot of interesting posts. How about 'Geomorphology of Gale Crater'? I have one or two ideas but many more questions, and I'd like to post them in a longer-running thread away from the day to day imaging discussion. Any other takers?
For starters, does anybody have a contour map of this place like the one at Meridiani with 5m intervals? ADMIN: You have your wishes fulfilled on UMSF (sometimes) |
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Dec 2 2012, 01:49 AM
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
If I don't say this as smoothly as I might otherwise, please forgive me. The thought racing around my brain delves into areas of physics about which I'm not completely confident.
First, it has struck me that dust devils form more easily on Mars than they do here on Earth. Considering how thin the air is and how cold the overall environment is, you would think there would be more energy available on Earth for such vortex formation than on Mars. But, I says to myself -- Mars spins around its axis at roughly the same speed as Earth spins about her own axis. But Mars is significantly smaller. Its surface is rather closer to the center of rotation than is ours. Would this not, based on conservation of angular momentum, mean that the coriolis force would be noticeably stronger on Mars? The spinning skater spins faster and faster as her arms are drawn towards her, and on Mars the difference in rotational speed between me and the spot 10 meters to the north or south is greater than at the same distance on Earth. And, if I understand the coriolis force correctly, it is this difference in rotational speed that drives everything from typhoons to dust devils to the swirl of water running down the drain. So -- if I'm reading this right and the coriolis force on Mars is noticeably greater than on Earth, encouraging a lot more atmospheric vortex formation, how would this affect simple aeolian erosion patterns on an early Mars with a much thicker atmosphere than now? Consider that in 6mb air pressure a modern Martian dust devil can pick up and entrain a pretty impressive mass of dust and pebbles. This process keeps much of the Martian surface swept clean of the ubiquitous orange-brown-yellow dust, the darker gray rock beds thus exposed forming the dark markings visible in telescopic images of Mars for more than a century. How much more erosive would a thicker atmosphere be, if an increased coriolis force makes it tend to form vorteces at every opportunity? This relates to the previous posts thus -- imagine Gale crater nearly filled with some form of fill. Then imagine a racetrack wind pattern running around inside the crater walls, breaking up into hordes of large dust devils which, due to the thicker air, are able to pick up tons of material and toss it high into the air? You'd have a pretty dusty atmosphere all the time (which would tend to cool the surface, I imagine), but such a wind pattern might be able to deflate an *awful* lot of material out of a crater in a pretty short time, at least in geologic terms. Maybe it was such a dust devil breakout phase that deflated a lot of crater fill on Mars? -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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