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Geomorphology of Cape York and Solander Point, Examining Opportunity's destination at Endeavour Crater
algorimancer
post Jul 8 2010, 03:19 PM
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A waterfall .... now, that's a neat idea. I'd envisioned a little rivulet gradually eroding the Wedge, but I rather like the waterfall idea.

A good stereo pair would be really helpful. That, or activate Oppy's heretofore unused (and undiscussed) JATO rockets to get there faster smile.gif
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JohnVV
post Jul 8 2010, 03:28 PM
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waterfall , i guess it is time to start to rethink my very old "blue mars" map so the next time some one wants to put it on a discovery chan show it will be " more" correct.
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algorimancer
post Jul 8 2010, 03:33 PM
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Well, I said a "good" stereo pair would be helpful. Here's a cross-eyed pair, using the last couple of images posted. These may be from the same image, for all I know, but I'm pretty sure I'm getting a stereo effect, particularly around the Wedge. Overall quality is not great, but it's something different.

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Phil Stooke
post Jul 8 2010, 03:39 PM
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I guess my reason for preferring a non-shoreline model is that I'm doubtful that an open body of water could have existed for long enough to create typical shoreline features like beaches, or that it would have been covered with ice, or that unconsolidated deposits like beaches could remain recognizable after all this time. Erosion might be slow on Mars but it can still have an effect on loose material. But I'll agree that other explanations than mine are possible, so let's see what we find. It might be interesting to consider what landforms or deposits you would expect the rover to see if this is a beach rather than superimposed layered sediment.

(PS this isn't distant vistas any more...)

Phil


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Bill Harris
post Jul 8 2010, 04:04 PM
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Phil, my take on this is the deposition of and differential erosion of strata of differing resistances, deposited as essentially flat-lying beds over a pre-existing hill. Use known processes and KISS until you have proof otherwise.

--Bill


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Stu
post Jul 8 2010, 04:49 PM
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QUOTE (algorimancer @ Jul 8 2010, 04:19 PM) *
A good stereo pair would be really helpful.


Ask, and ye shall receive...

http://roadtoendeavour.files.wordpress.com...-york-in-3d.jpg


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Stu
post Jul 8 2010, 04:51 PM
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QUOTE (Phil Stooke @ Jul 8 2010, 04:39 PM) *
(PS this isn't distant vistas any more...)


I think discussing Cape York here is valid, as we're all just waiting to see it appear on the horizon as part of the "distant vista", but if others agree with you then I'd be fine with someone starting a "Cape York" thread.


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ElkGroveDan
post Jul 8 2010, 05:02 PM
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QUOTE (Stu @ Jul 8 2010, 09:51 AM) *
I'd be fine with someone starting a "Cape York" thread.


So let it be written, so let it be done.


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algorimancer
post Jul 8 2010, 05:26 PM
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Great stereo, Stu (much better than the one I improvised). The more I look at this, the more I think "beach". Consider that, if Endeavour were flooded, with the water extending beyond the current rim (so that Cape York was an island), the big open deep water would be to the east of Cape York, and consequently the major wave action would be from that direction. All along the east side of Cape York is what appears to be a longshore bar, which might be expected from that wave action. This feature is largely lacking to the west. It makes sense that, as the water declined, water which accumulated behind the bar would channelize and flow through gaps. While the Wedge seems most prominent, I also see signs of channels to the south of it (immediately below the apparent small crater in the "bar", and a smaller channel at the northern "point" of Cape York. I see signs of channels feeding into these 3 outlets which are traceable southwards beyond half the length of the Cape.

Here's a portion Wikipedia's description of beach geology:

"There are several conspicuous parts to a beach, all of which relate to the processes that form and shape it. The part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more longshore bars: slightly raised, underwater embankments formed where the waves first start to break.

The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (sand size or smaller) , winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune."
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Stu
post Jul 8 2010, 05:30 PM
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QUOTE (algorimancer @ Jul 8 2010, 06:26 PM) *
Great stereo, Stu (much better than the one I improvised).


Thanks, but can't take credit for that; I just used the IAS Viewer to view the already-existing anaglyph of the area, then stitched together four close crops of it. Thanks to the amazing HiRISE team for the stunning images! smile.gif


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ngunn
post Jul 8 2010, 06:34 PM
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Back to something I mentioned before but, since at last we have a special thread and more people contributing, here it is once more. It's about the beach/not-beach issue. One sure way to demolish the beach idea is to show that any hypothetical Endeavour lake would have had an outflow at a lower level than this terrace. If on the other hand the outflow point is found to be very close to the level of the terrace this could be seen as a 'fulfilled prediction' of the beach hypothesis. Lakes that drain can have levels that are stable for long periods, whereas lakes that don't tend to fluctuate or steadily decrease in level, militating against significant beach formation like Phil said.

I'm surprised that no-one here has seriously grappled with the relative elevations. I've made my own clumsy attempt and I think the elevations are fairly close - but that's really not good enough.
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algorimancer
post Jul 8 2010, 07:57 PM
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QUOTE (ngunn @ Jul 8 2010, 12:34 PM) *
...I'm surprised that no-one here has seriously grappled with the relative elevations....

It seems like Google Mars with the MOLA elevation database and overlaid high resolution imagery ought to get close to an answer. It's too bad it doesn't have the explicit capability of adding a water layer at a particular elevation, though this might be improvised (I'm afraid I just don't have the time lately, else I'd try it). One issue with applying this to ancient times may be that previously saturated subsurface/sediments may have subsequently lost water to sublimation and consequently altered the topography.
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Ant103
post Jul 8 2010, 10:26 PM
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Okay……


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djellison
post Jul 8 2010, 11:18 PM
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I'm wondering if you could take word-pedantry to another website. Please, just don't have that discussion here, yet again.
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sariondil
post Jul 8 2010, 11:19 PM
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QUOTE
I'm surprised that no-one here has seriously grappled with the relative elevations.


Here is an attempt using a DTM from HRSC data (H3198_0001_DT4.IMG), blended with the nadir view (H3198_0001_ND4.IMG). The hypothetical shoreline in shown in white. It is more or less equivalent to the -1480 m contour (estimated from Google Mars because I introduced some sort of offset during file convertion). I canīt find a contour that completely surrounds the hill in question, but that may be because of the resolution of the DTM.
Still, this contour line implies a maximum depth of about 410 m for the lake, and some lagoons along the east rim (anyone want to look for shorelines?). Also, at this lake level the hypothetical lake would just begin to spill into a large basin to the southeast (along the red arrow; the contour lines begin to connect if the lake level is just a few meters higher). If the lake really spilled in that direction, I would expect to see some channels; but at a quick glance I donīt see any.

EDIT: Used the correct data set now and changed attachment accordingly.
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