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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Jun 14 2019, 12:33 AM
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Senior Member Group: Members Posts: 1045 Joined: 17-February 09 Member No.: 4605 |
Given the height of the Gale crater central peak the development of a peak ring is unlikely since this is predicated on the collapse of the central peak.
There is clear evidence that the sedimentary formations investigated by Curiosity since landing predominantly reflect fluvial lacustrine environments and the accessible 300 metre odd thickness of the Murray formation was laid down over some considerable time in a reasonably deep, neutral pH lake. We do not know just how deep the Murray formation extends; or indeed if it is actually the basal layer of Mount Sharp or whether beneath it is a sedimentary formation reflecting the environment you describe. Certainly the veins and halos indicate that there have been extensive hydraulic fracturing and deposition incidents, primarily alkaline but in the lower levels acidic on occasion. The clear transition from the phyllosilicate bearing Murray formation to the sulphate bearing layers represents a change in the local environment from water dominated to arid, acidic conditions. But there is clear evidence of significant water, both surface features and groundwater well into the Mount Sharp erosion period. For example hydraulic fractures extend across the contact between the Murray formation and the much later, aeolian Stimson. The thing I think we all struggle with is the timescale represented by the sedimentary layers of Mount Sharp and the subsequent erosional end state of Gale crater. On Earth we have only fragments of the Eoarchean crust which date to the time of the Gale impact. The evidence of long standing surface water on Mars presents a real challenge to the traditional view of the early solar system. |
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Jun 14 2019, 02:45 PM
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
Hypothesis - Vera Rubin Ridge's odd chemistry is the result of the ridge's location above the inner ring of Gale crater; hydrothermal activity concentrates at crater peaks and rings, so the ring is associated with mineral deposits. Water flowing down through sediments leached minerals into the overlying strata which alter the overburden to create the erosion-resistant Vera Rubin Ridge.
Given the height of the Gale crater central peak the development of a peak ring is unlikely since this is predicated on the collapse of the central peak. Not necessarily, the peak ring can also be an uplift effect. QUOTE A MASSIVE CENTRAL PEAK AND A LOW PEAK RING IN GALE CRATER – IMPORTANT INFLUENCES ON THE FORMATION OF MT. SHARP. Gale’s central peak and peak ring were emplaced immediately after the impact, and influenced the subsequent history of deposition and erosion that formed Mt. Sharp (snip) Spray et al { Spray J. et al (2013) LPS XLIV, Abs. #2959.} suggested that a peak ring in Gale crater could have influenced the location Mt. Sharp’s lower segment by localizing the deposition of sediments. This effect could account for the fact that the northern, eastern, and western boundaries of Mt. Sharp correspond to a ~ 80 km diameter circle (Fig. 4). https://ntrs.nasa.gov/archive/nasa/casi.ntr...20150001905.pdf Also important - Gale crater's rim and floor tilt down towards the North. Assuming this is not due to post-impact subsidence, that suggests the breccia reservoir is also tiled, and the Northern edge of the reservoir is deeper than the southern edge. It seems that rain or surface water could flow into the central ring, so water in the sloped 80km diameter inner ring would have collected into a crescent-shaped lake along the Northern edge of the inner ring. That water would have percolated through the warm outer ring breccia, experience hydrothermal alterations, and then exited at roughly the location of the current Vera Rubin Ridge. Surface water from a large area enters Gale from the southwest and flows clockwise across the area between the inner and outer ring. This would seem to suggest that 2 different types of water 1-hydrothermal springs associated with the northern arc of the inner ring, and 2- surface water flowing across the crater floor from the west, would have mixed in roughly the location where we now find Vera Rubin Ridge. The early hydrothermal system could have created acidic mineral deposits along faults and along the inner crater ring. Those minerals could leech out and cement later lake sediments. Another interesting article on impact crater hydrothermal systems, this one specific to Gale Crater Gale Crater: Formation and post-impact hydrous environments https://www.sciencedirect.com/science/artic...1274?via%3Dihub |
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