Geomorphology of Cape York, Examining Opportunity's destination at Endeavour Crater Options

[Stu]

Everyone, say hello to Cape York... in colour...



Larger version on my blog: http://roadtoendeavour.wordpress.com/2010/...-york-in-colour

[Gladstoner]

After seeing the jumbled mess that Opportunity is now sitting upon, I decided to tweak my guesswork a bit.

The Cape York bench edge appears to be an old erosional surface.

A very simplified geologic history....

Original Endeavor crater surface, at Cape York:



Meridiani sediments laid down. I'm not sure if the original thickness of this stratigraphic sequence has been determined:



Over time, these sedimentary rocks are eroded and covered with ejecta (made up of the same rock):



With more time, wind eroded the ejecta deposits and remaining bedrock exposures, into the flat Meridiani plains:



Opportunity sits upon the ejecta deposit. The Cape-York-terrace erosional surface/horizon continues beneath the surface (and under where the rover now sits). Occasionally, as at Endurance and Victoria, the solid bedrock is uplifted to the surface by large meteor impacts. Otherwise, most of the 'bedrock' observed is just more of the jumbled ejecta.

The smaller impact craters are mostly or entirely within the ejecta deposit.

Where Opportunity now sits, the bedrock is relatively thin. Further out (eg. at Victoria Crater), the bedrock is much thicker (not shown in the drawings).

The ancient rim of Endeavor, on the other hand, is made up of more resistent stuff, as is readily apparent. Here, it acts as a 'canvass' for the Meridiani 'paint'.

[centsworth_II]

....Over time, these sedimentary rocks are eroded and covered with ejecta (made up of the same rock)...

I'm not too sure about the ejecta layer you talk about. Over Opportunity's route, every time rock is exposed it appears to be a pavement of the originally deposited layers, not a bed of ejecta. The only significant ejecta seen is around some of the fresher craters and that is sparsely spread around the crater, not forming a layer. I don't think the sulphate rocks are durable enough to build up an ejecta layer. The only layer build up on the surface of Meridiani seems to be dust, sand and berries.