I joked previously that maybe Cape York is nothing more than a stain on the ground. It looks like I wasn't far off.

Thanks again, Pete. Those profiles certainly look consistent with each other. Subtracting off the overall slope, the tallest section (blue) gives around 15 metres height, which is starting to sound reasonable:
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... Meaning Cape York is well "climbable" by Oppy to get a better view (and to get a nice panorama) from its top : Endeavour's far rim and the other capes should give us a gorgeous view. Like many, I'm drooling over this upcoming view. Yum-Yum ! ... a "Yum-Yum" Pan. Bon Appetit ! (besides, it's lunch time right now in France)

Looking at that 3D view, Cape York seems less like a hill to climb, and more like a ledge to drive out onto. I am so looking forward to arrival day. I almost wish I could fast forward to that event. Except that would probably mean winter is just starting again, and I am really, really tired of winter right now.

What are you talking about? Arrival time will be by Easter

Fred, I'm not sure I follow your logic here. Wouldn't a line of best fit along the plains approach section of the plot give the baseline to estimate the height of Cape York above the plain? I make the maximum height of the blue plot to be around three to four metres?

You might be right about that, but I think we'd need to see how the profiles look farther out to know for sure where the plains "start". And as others have said, if that overall slope is right, this isn't a hill, it's more like a ledge to drive out on.

Ok... trying to get my head around this... We're now thinking that Cape York isn't so much a "hill" as a kind of a "ledge" or platform sticking out from the inner slope of Endeavour...? Does that mean the hills that curve around the southern edge of the crater are the same? This is fascinating...

On another note, it was pleasing to find a LOT of interest in the MER mission last night when I gave an Outreach talk out at a little village just outside Kendal. "Mature" crowd, shall we say, general level of interest in science, but still, the ones who were aware that there are rovers on Mars were fascinated by them, and very impressed by what they've achieved.

So say we all.

The perennial problem with visual representations using axis with the same metric but different scales is the gut reaction 'gee that's steep'. It isn't a particularly steep gradient and rather than a ledge overlooking a chasm it is more of a low ridge with a (roughly) ten degree slope into the crater.

Gotcha, thanks.

Still... hill... ledge... island... ledge...

I need more tea.

That's right, Stu. The profiles in pgridrods's first image in his post above show it very nicely, even if the vertical and horizontal scales are not identical. Those profiles are essentially showing that Opportunity will not really need to climb up to get on top of Cape York. The idea to take away from this whole discussion is that Opportunity should be able to drive right over the top of Cape York with little trouble, unless boulders or loose sand block the way. The steepest slopes are on the back side of the Cape, and those apparently average 7-9 degrees.

Regarding the hills to the south, his topo maps posted above and earlier in another thread show them to have much more significant topography.

Thanks cosmic; I had read those posts... I was just recapping whilst virtually banging my head against my computer screen!

I've just been messing about on using Google Mars with the latest .kml file, and if you stretch the vertical exaggeration to 3 the true nature of Cape York becomes clearer...


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When you look at it more closely it looks like material flowed and rolled over Cape York from the west, doesn't it..?

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Stu. I see what you mean. The NW rim has been eroded flat and the Meridiani sulphate sediments have flowed into the crater. Flowed tends to imply fluvial action but that terrace around Cape York does remind me of a shallow shoreline, sandbar – rip channel system. Vikingmars’ "Dagger Valley" at the North end fits that scenario as a rip outflow channel. Cape York may be topography challenged but it is a fascinating destination.

Stu - or anyone handy with Google Mars - can you identify the hills on the horizon behind Cape York in your two lower views?

Wider angle view...

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Remember, tho, that everything is vertically stretched x3

You have to be very careful when looking at elevations using Google Mars. As I and others have pointed out, most of the topographic information used in Google mars is based on the MOLA coverage, which is not uniform, and typically not very closely spaced. Large stretches of Endeavor's rim were not sampled at all by MOLA shot points, so elevation maps derived from them do not display accurate elevations where topography is changing rapidly between MOLA lines and sample points. Emily posted a very nice kml file that will display those shot points in Google Mars. I think it was in the Distant Vistas thread.

One area of Mars that has higher frequency elevation coverage in Google Mars is Victoria Crater. That area has been populated with a digital elevation model based on more closely sampled points, probably based on a HiRise stereo pair. If you look at Victoria Crater in Google Mars you will see much more topographic detail than most anywhere else.

Oh I agree, absolutely. I don't rely on GM, good as it is, for anything. But it is useful for giving a 'general impression' I'm sure you'll agree.

Thanks. So, am I right in thinking that's part of the Miyamoto rim in the background? (Sorry, OT I know.)

I'd like to remind those of you engaging in this discussion of this post in which I brought all of the available MOLA ground tracks into Google Mars. You can see that all the ground tracks completely miss the entire western rim of Endeavour, so the MOLA data simply doesn't record the elevation of the rim. It's not in the data at all. It would be a much more productive exercise to do photoclinometry or develop a DEM from stereo imaging, as pgrindrod is trying to do...

Oh, heck, we were just having a bit of fun speculating.

But ok, I'll go tidy my room...

... and while you are up there write out 100 times THERE IS NO MOLA DATA FOR THE RIM OF ENDEAVOR CRATER or there'll be no wandering around that castle of yours in the dark this evening, young man.

Just to add to the ways of getting across the geomorphology of Cape York, here's a red-blue analglyph of my Cape York DEM (plus contours).

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And just in case that isn't overkill, here's a movie of the same area.
You Tube animation - Cape York

As you can tell, the resolution is turned way down in that movie (still managed to crash my computer several times!), and I don't yet have my pilot's licence. If my computer doesn't melt, expect a flurry of these things.
Pete

Nice, Pete; but I think you got the red and cyan layers reversed. We can put our glasses on backwards to make it work, but if you are going to crank out a flurry of these things it might be best to reverse the colors. Thanks for all the good work, by the way.

The animation was very effective.

Excellent movie and anaglyph. But yes, the red and cyan layers need to be reversed, or we need to wear our glasses upside-down.

While we have seen very nice DEMs and a couple of lower-res anaglyphs of Cape York, I just thought an anaglyph in original size would be interesting for comparison. Only the north part was able to be included here within the maximum upload size, however I hope it's worth it.

Now that we're officially "on our way", I thought it might be useful to compare the size of some of the major features and landmarks on Cape York with Oppy, so here you go... You'll see some orange "spots" on the landscape when you zoom in on it. The dark pixels in the centre of the dot shows the size of Oppy. Not easy to see, I know, so I'll post a higher resolution version on my blog later...

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As usual, this is intended to be a rough guide, not a definitive one.

Update: large version posted to my Twitpic account: http://twitpic.com/4fckki/full

While we are waiting to see Cape York, some Geology questions...

Cape York is lower than our present position (if it wasn't we would already see the peaks of Cape York above the horizon).

So... Will Cape York be covered in sulfate deposits and blueberries?

If 'Yes', then how come Cape York looks so distinctive from orbit with clear boundaries to the plains of Meridiani? If it was covered in sulfates and berries like everywhere else CY should appear as just a nondescript smooth bump.

if 'No', then how can you have Cape York be free of sulfates and berries if it is lower elevation than our current location? If Meridiani was created by a pool of evaporating water, then CY should have even more deposits on it than we see where we are now since it is at a lower elevation. Basically, how can you have an 'island' that is below the sea bed!? Presumably CY has not subsided... Note that from space CY shows different materials (such as clays) which implies that it may not be covered with sulfates and blueberries.

I am not sure what the answer is to this dilema. Does anyone have an explanation? One thought I had off the top of my head was that the sulfate deposits are from groundwater seepage (as has been proposed) with a geology sequence something like..

1) Endevour impact
2) vast deposits of basaltic sands introduced (which we see are underneath the thin sulfate deposits here)
3) sand gets blown around and out of Endevour crater so that around the rim there are sand deposts that are higher than the actual Endevour impact crater rim (ie higher than CY)
4) sand is also blown off CY or never even accumulated on it
5) water seepage comes to the surface, depositing sulfates, but water does not seep 'up' CY because it is too far for water to seep upwards and/or because it is made of impermiable rock instead of basaltic sands
6) water seep stops, sulfates erode leaving blueberry lag depost (except on CY )

So, I think it will be very interesting to see if CY has blueberries/sulfates on it or not....

Thoughts?

-Ben-

I am no planetary geologist and therfore may not be knowledgable to answer such queries but I think that CY forms part of endeavour crater rim and thus represents material excavated from deeper layers on Mars which presumably contain the clays which predate the sulphates!

Yes, but at one point the sulphate layers covered Cape York. They have been eroded away so I would expect to find blueberries that eroded out of the sulphate layers on Cape York but I would expect little left of the Sulphate layers themselves. As for why the Meridiani plains leading up to Cape York are higher, I guess it's just a matter of differential erosion rates due to the prevailing winds over the topography of the crater.

This is quite plausable. In this case we should see a blueberry lag deposit directly on the clays (ie the sulfates are all gone in places). Blueberries over clays (and other CY rim materials) would look different than blueberries over sulfates & sands (which we are driving on) and would explain why CY is destinctive looking even though it is lower than the plains.

There has been no mention of a hematite signature from Cape York. Wouldn't a blueberry lag deposit produce such a signature?

The CRISM composition data certainly don't seem to point to a blueberry layer on Cape York... but it's certainly legitimate to ask why not, if the whole area was covered with the plains material and it has eroded away. One possible explanation - blueberries were more common in some areas than in others, and this may be an area where they were not found to begin with. Test - look for blueberries in the plains immediately adjacent to the Cape.

Phil

If that is indeed the case, ie no berries/sulfates on CY while berries are [presumably] on the plains right around CY, then we have a head scratcher here and this might point more towards a groundwater source of the sulfate/hematite instead of an evaporated body of water (which would have had to have covered CY since CY is lower than the surrounding plains) as I proposed in my original post.

Note: I am not a Geologist, but my dad is... :-)

-Ben-

That might not follow. Flood waters pouring over a cliff will take the path of least resistance, and will avoid locally higher obstacles. It is only if the entire area was submerged that CY would necessarily have been covered.

Perhaps the berries rolled downhill into Endeavour, assisted by winds?

Moderators: perhaps this discussion should be moved to the "Geomorphology of Cape York" thread?

The topography inside Endeavour would seem to indicate that the sediments flowed into the crater from the NW. The contours also seem to indicate a slightly steeper channel just to the south of CY. It is pretty clear that the blueberries formed within the sediments and whether there was just groundwater or whether there was a surface water overlay would seem immaterial. Low profile notwithstanding the feature is fascinating, but concentrating on the geomorphology of Cape York in isolation rather than standing back and considering it in the context of Endeavour Crater as a whole could be a bit limiting.

Two interpretations of the terraces of Cape York:

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The prominence of the terraces was exaggerated for the sake of illustration.

Interestingly, one yields higher strata, while the other exposes deeper layers.

This Pancam from sol 2658, about 1200 meters from Cape York, shows plenty of berries.
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Does CRISM really show no hematite signal from Cape York, or is it just that that is not where the focus of attention is at? Phyllosilicate and hydrated sulphates are the focus, but does that mean the hematite is not there or just not being talked about?

I think I will be more surprised to see few berries on Cape York than many. Just because I think The Cape was covered by the same berry containing layers that eroded away and left berries over the rest of Oppy's route. But maybe berry forming layers never did extend over Cape York. It will be interesting to see.

I hope you don't mind my fooling with your diagrams to better reflect the elevation between Cape York and the adjacent plains. (I'm sure Phil would do it if he had the time. )
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That's all right.

I knew I could count on someone here to do a proper elevation profile.

More thoughts on the Cape York strata:

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Here, they are shown as hogbacks dipping away from the core rock of Cape York.

Varying resistence to wind erosion of the layers would leave them at different levels on an erosional surface.

Most resistant of all is the old crust (orange) exposed in the hills and mountains that make up the rim of Endeavor.

The light unit (yellow) seems to be more resistant than the other strata. There may even be a thin cap rock (shown here in maroon), which can be seen in places as a thin whitish line on images of the outer edge of the terrace.

The next unit up-strata (gray) is less resistant and forms a shallow trench.

The lower (gray) unit appears to be less resistant as well and would form a very interesting unconformity above the (orange) material. Some of this (gray) unit could be drifts and debris from the hill.

Further up the section, the thin (bronze) unit could be 'softer' still, a stratum that is particularly prone to erosion. In any case, it seems to be a significant bedding plane of some kind. A second, similar feature may lie above the (yellow) unit just above the 'cap rock', as a similar trench seems to occur in places.

Further up (and down-slope), the layers continue, but they tend to be covered by debris. Some of these layers could be similar to the (yellow) layer, but here their dip would be closer to horizontal, leaving a more ambiguous surface expression of the units (as it is over much of Meridiani).

Further away from Cape York, there are likely deeper strata that are not exposed at this location.

(For the sake of simplicity, I didn't include the slope of the surface surrounding Cape York.)

Just for fun, here are the layers as they might appear if they were level and eroding on a steep slope:

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I think I like your very first diagram the best (post 87 here). It explains the similar unit at the margin surrounding the central material of the ancient rim.

I'm not sure how I see that the interior layers could get bent to follow the crater interior. The initial whack should've gouged a big hole, and any layers that formed afterwards should have been dropped in parallel and flat. Any tilting after that would be uniform across the region...and you should see that as a difference in remnant rim heights.

I was thinking along the lines of something like this:

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In the previous illustration, I was concentrating on the surface expression of the exposed layers. I exagerated the dip of the layers for illustrative purposes. Perhaps I was too simplistic in showing the subsurface nature of the contact.

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:

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

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

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

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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'.

I'm not sure, but I think the uplifted rims of Endeavour were subjected to erosion and probably made a local mantling deposit at the base of the rim crests. Then additional materials were laid on top of that too. Then it was exhumed as you've described in your drawing.

(So take the drawing you did on June 18, then add a layer on top that then gets exhumed.)

Do you mean like this?:

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The wonderful thing is that we will soon find out....

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.

centsworth_II: There was an ejecta layer at Victoria. There's not a continuous deposit across Meridiani as the drawing suggests, but at Victoria we drove over the planed surface of the ejecta blanket and also saw it in cross section on the capes. It should be drawn as a discontinuous layer. I agree that on many of the ancient craters the ejecta has been removed (Erebus, for example), but I think it is ok to show it schematically.

The Victoria ejecta was highly localized, as is any of the ejecta on Meridiani as I see it. I could have it wrong, but here's the way I see it:

Ninety percent of the Meridiani that Opportunity has shown us is characterized by a fractured sulphate pavement covered by a thin ripple layer of sand. I think this sulphate pavement is unmoved since it was formed from wind deposited sediment layers, subsequently acted on by water. I don't think it is a bed of ejecta.
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Just adjacent to Cape York, this sulphate pavement seems to be a little jumbled. But I still think it is essentially the original wind placed Meridiani layers, not redistributed ejecta. Of course, I could be wrong.
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So you are thinking that the Endeavour ejecta is buried deep below the "Meridiani wind deposited then aqueous-altered" layers and probably not well exposed?

Below the yellow and brown layers in Gladstoner's graphic (which I really like, BTW).

(...Makes sense to me.)