Geomorphology of Gale Crater, Rock on! |
Geomorphology of Gale Crater, Rock on! |
Sep 26 2012, 10:22 PM
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#1
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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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Nov 28 2012, 04:48 PM
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#2
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
One feature very common to Gale crater, both its floor and on the central mound, is "inverted topography," where there is something that looks like a stream valley (with dendritic tributary or distributary features), except that it stands higher than the surrounding terrain, rather than lower. That is generally interpreted to mean that there once was a valley, whose fill was, for whatever reason, more resistant to erosion than the material into which it carved. The fact that it stands high now tells you that the whole surrounding landscape has been deflated, eroded away, since the last time there was significant fluvial activity here.
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Nov 28 2012, 05:12 PM
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#3
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Newbie Group: Members Posts: 7 Joined: 18-September 12 Member No.: 6655 |
the whole surrounding landscape has been deflated, eroded away, since the last time there was significant fluvial activity here. One thing that I don't quite understand is where did all the eroded surface go? Does it have places where it accumulates preferentially? How many meters of surface can we expect to be removed in 2-3 billion years? At some point the erosion stops because the landscape is already covered with sand, so there must be some upper and lower limits to this phenomenon. |
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Nov 28 2012, 06:25 PM
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#4
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
One thing that I don't quite understand is where did all the eroded surface go? Good question. I don't think anyone knows yet. From Malin and Edgett, "Sedimentary rocks of early Mars", Science, 2000, http://www.sciencemag.org/content/290/5498...&siteid=sci (italics mine) QUOTE Not only is evidence of the depositional processes not apparent, neither, in most cases, are the processes that exposed and eroded the layered and massive units (with the obvious exceptions of faulting in the Valles Marineris and the presence of yardangs that imply wind erosion). For example, Henry Crater contains 10,000 km3 of material in an isolated mound within the crater. This material is layered and stands nearly as high as the crater rim. This observation implies that some process or processes have removed 15,000 km3 of material from Henry Crater. Notwithstanding recognition of morphologies that suggest an apparent sequence illustrating removal of material from impact craters, the actual processes are unknown. The implication is that most of the exposure and erosion of the layered units must have occurred some time far in the martian past, when transport out of the craters (again, with no obvious transport pathways) could have occurred via processes not acting on the planet today. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Nov 29 2012, 06:45 PM
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#5
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Member Group: Members Posts: 154 Joined: 17-March 05 Member No.: 206 |
Good question. I don't think anyone knows yet. From Malin and Edgett, "Sedimentary rocks of early Mars", Science, 2000, http://www.sciencemag.org/content/290/5498...&siteid=sci (italics mine) QUOTE (ddan @ Nov 28 2012, 10:12 AM) * One thing that I don't quite understand is where did all the eroded surface go? Well, I can think of 2 methods: 1. Ice / Glaciers - After Gale formed, water entered the crater, creating a lake, which then froze over with the central mount sticking out. Sediment accumulated over the ice in layers (and the central peek), essentially filling the crater 'to to the brim'. Later, perhaps as the Martian atmosphere lost most of it's density (or the polar tilt moved Gale from polar region to equatorial) the ice sublimed away, sinking the floor down, but maintaining the central peek. 2. Fractured/Soft Material - When Gale formed, the rock under the crater floor had less strength then the central peek. The crater filled up with sediment over time, again near the rim of the crater. However, over the eons, all that weight compressed the original material in the crater floor, in effect sinking or slumping the floor away from the rim and central peek. Just my 2 cents! |
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