Going on the orbital imagery - and the pointing - I'd say it's little bits of southern erebus, but there's lots of bits and pieces like it all around.

Doug

Bill and Doug:

Are you both talking about the same things, but with different names, or not? If you see what I mean.

Some nicely aligned outcrops would be a Good Thing, I think...

Bob Shaw

There's a full filter sequence for one frame, but there was an L257 for all the frames in that little mosaic just about, that's the data I'm refering to. it's down at the tracking site in thumbnail form, nothing more yet.

Doug

Do we know which feature was called 'Zane Grey'?

Phil

The full L23567 sequence is for one frame so far, but that will give us geo-geeks a good start on figuring out the lithologies here.

Bob, it _is_ confusing. The horrid 25 Feb route image was done on another 'puter using Winders Paintbrush and is linked to below. Oppy is at the area marked "Sol 742" and is moving, AFAIK, southward. The outcrops we are looking at now are to the map's left. "Payson", proper, as I understand it, is that large promontory of bedrock South of the word "Payson" on the map. We are currently at some dinky outcrops before the major outcrop sequence at Mogollon-Payson. The major outcrops are on the other side of that dark-toned sand dune we've seen on approach. This whole bedrock exposure is the Mogollon Rim with Payson being a locality within the Mogollon Rim, and I'd be inclined to call this outcrop and the next outcrop on the horizon "Mogollon" and call that promontory area "Payson". But the tendency here is to call this Payson, so I'll go along. I have no idea what Cornell/JPL is calling this current location.

"Burb's of Payson"?

ADDED: Phil, I don't know this as fact, but I have the impression that "Zane Grey" is one of the bedrock exposures between Purgatory II and this stop. You can see them on the righthand color image in my Post #80.

--Bill



S742 Route Map

I think Zane Grey was the midpoint between here and Olympia - where we stopped up between drives.

Doug

I may have missed this from some earlier posts, but has Opportunity traveled outside it's landing target ellipse yet?

Yes.

Excellent. Thanks!

>> but has Opportunity traveled outside it's landing target ellipse yet?

Yeah !
and that's the really great/new thing with the MERs: a single rover almost makes up for *multiple* spacecrafts landed on different parts of the planet

(provided it is sufficiently used for what it's made for: roving

IIRC, the landing ellipse crosses Erebus at its southern rim.
Here is a previous post: http://www.unmannedspaceflight.com/index.p...indpost&p=31084

So the answer is "not yet".

http://www.msss.com/mars_images/moc/2004/0...Ellipse_25m.gif (many meg)

Not so hasty - the ellipse goes to the Southern edge of Erebus - I'd say we're within a hundred M of it perhaps - but I wouldnt say we've crossed it as yet.

If you go to the larger image ( the 10m res one ) - and overlay some good MOC imagery - it's a close call.

Doug

But ... i saw a image which shows the boundary in the northern Erebus.

Depends what you call the ellipse. The Pre-launch ellipse, the most launch ellipse, or the entry ellipse.

http://marsoweb.nas.nasa.gov/landingsites/...l/HematiteWest/
specifically - http://marsoweb.nas.nasa.gov/landingsites/...ps/Hematite.jpg


I'm not sure which one is on the MSSS imagery, but given that Opportunity was comparatively late in it's launch window, it's likely to be more the red ellipse with closed lines than anything else.

Using this one...

http://marsrovers.jpl.nasa.gov/gallery/pre...LAD_3A-A0R1.jpg
Which is a pre-entry ellipse, the ellipse is much smaller and thus yes, Oppy crossed over that one some time ago - but personally - the ellipse I'd use is the one they had down before launch.

Doug

If you look carefully at this Opportunity sol 744 pancam image, you can actually see the landing ellipse in the background, so no, the rover hasn't reached it yet.

LOL!

This is coulorized Sol744 R1 PanCam mosaic (70% original size): Click to view attachment

and this the vertical stretch (3x), slightly cropped version: Click to view attachment

I like especially last one. The horizon seems really close especially in the right portion, so we are very close to highest elevation point..

MBB is downloading sol 745 images. Exploratorium must be working again

In fact (very rough NavCam stitch)..

Wonderful stitches, Dilo.

The Sol 744 3x-stretched is interesting. The exaggeration emphasizes surface textures. In this depression (which I think of informally as The Valley of the Shadow of Death) befoer us, note that many of the paving stones have the sand rings around them. Not unusual, many do. But some have the "sand sapping" feature going through significant ripples. Which suggests to me that there maybe a lot of sand going somewhere.

--Bill

The rover drivers prefer the first one.

impressive view ...
here is a lens corrected and colorized version:

So here we are at last! Thanks, Nirgal. The range of contrast makes it look almost 'snow-capped'. What seemed so black at a distance, apparently wasn't all that distinct from the upper part. Just lots of lamination overhangs shadowing the sides. To be honest, I can't discern more than one laminated unit in this exposure.
I haven't spotted any 'festoons', either. Maybe we won't have cause to linger here long. One close-up view might tell the whole story. Anybody got other ideas?
Victoria beckons!

Wow - that is now one of my new favorites - great job!

Here is an L257 color image of the Mogollon outcrop from Sol 744. Nothing that astounding, although I did expect the bluff unit to be a bit darker than the overlying unit.

This is going to be a good area to study-- we have likely found our marker bed to correlate with.

--Bill

Hey, Bill, you're teasing us non-geologists with that kind of expression. "Our marker bed to correlate with." Please, explain to us what you mean by "marker bed". How is it distinctive from lots of other laminated evaporites we've seen since touchdown? If we are confronted with a five-meter exposure of laminated evaporites at Victoria (Oh God, Please let it be!), interspersed with 'festoon beds', volcanic tuffs, and other things I can't even imagine, how will we pick out this marker? Prof. Tim, can you help out explaining to us The Erebus Story ? I do think a lecture is needed.

Just an explanatory note: The dunes behind Mogollon rim appear higher because they are on higher ground than Oppy currently, right? They aren't such monsters as they appear

I think so.

As a side note, see what would happen if Oppy is on a leveled terrain with dunes actually high like that: A very close horizon and the view blocked by the dunes i.e. a maze. Let's hope there is nothing like that on the way to Victoria.

I think actually - some of these are biggies - as big as the ones we saw before on the North rim and skirted way north around.

I don't think they'll come up to camera height - we'll always be able to see over them, but we might have difficulty in planning longer drives

Doug

This is the current position (sol 745) as seen from the previous one (sol 742).

Click to view attachment (117k)

Finally, the sol 744 pancams I was dying to see have arrived. The dipping beds I saw in the sol 742 navcams and described in post #73 are much more evident in the pancams. Fracturing and cover still make many of the contacts difficult or impossible to follow, but the geometry of the layering is apparent. Moving from right to left across this panorama, progressively younger layers come to the surface. I've used dashed and dotted lines to highlight the attached, cropped and annotated segment of my Autostitched panorama from the sol 744 L7 images.

Stay tuned!

Tom, the bedding geometry is quite apparent in this exposure and likely represents at least a local dip if not regional-- the orientation appears to be along the Erebus crater rim, so I don't think it reflects the upturned strata of the crater. We'll know more at the next Payson exposure, which is as prominent as this one from orbital imagery. Of equal or greater interest to me are the near-vertical joints and fractures.

>pancam_Payson_12x1_L7R1

Ah ha, so the NASA/JPL designation for this site _is_ Payson.

The dunes to the West and South are higher and appear moreso due to the view from _inside of_ Erebus. I'd suspect that this is due to orographic effects from the crater rim causing more sand to be deposited.

Again, if you don' t understand, Google is a lantern in the sea of enlightenment.

--Bill

Two pancam images from Sol 744 are tweened here in a Flash movie for a sense of the topography of these dunes. It's hard to triangulate to the ridge line that make up the horizon, but it looks like 150 - 200m away (with the outcrop back edge at about 40m from this vantage point).

Personally, I'd leg it up a dune for a good look to the south towards Victoria to see whether this is a real high point on the road to the south, or merely a matter of viewing from a dip, but then if I'd been driving Opportunity the mission would have ended months ago...

Andy

Your annotated image showing the dip within the unit below the planar beds is good. IMO the subsidence is fairly recent because you can see a point along the escarpment in Nirgual's image where the lower beds form a wedge and vertical displacement dies out further to the right. Illustrated by horizontal continuity of the upper planar unit. The lack of rubble off the cliff is also further indication of its age

The "drive-direction" pancams from sol 745 are available at the exploratorium: http://qt.exploratorium.edu/mars/opportuni...cam/2006-02-28/

Check for yourselves, but imo Oppy will take the route to the right of Payson i.e. by the top of the rim.

These images show the unconformable and in some places rather complex relationship between the upper and lower beds. I look forward to panorama of this series.

I was hoping that Oppy would walk this outcrop but evidently the operators feel it may be safer to not traverse the trough.

Oppy has the IDD deployed; note that the flat rock to the left of te tool cluster has been displaced.

--Bill

http://qt.exploratorium.edu/mars/opportuni...3IP1152L0M1.JPG

I love how adaptable the rover controllers are with the rovers' various ailments. Programming problems, low power in winter, sticky wheels, a broken switch, a fussy spectrometer, and now a broken motor winding. All that, and the rovers just keep going.
Fast forward to sol 1500, when Opportunity is just dragging itself along with its single working wheel and one working instrument. "Keep goin' little feller!"

Well folks. It would appear I somehow managed to confuse the multi-quoter. Sorry about that.


Well a regional dip would be consistent with a prior SS comment that the Oppster has been climbing stratigraphically as we've gone south. At this location I have seen quite a bit of variability in the dips, so I am suspecting local, perhaps on a regional trend. The dips I highlighted may simply be dunes/sandsheets filling paleo-depressions, or maybe a channel filling.



If I haven't already said it, welcome to the forum, neb. I've enjoyed your comments, but I don't know where to look to see the things your are describing. It would sure help some of us if you'd post an annotated image with some of your comments. I'm not sure I see the upper planar unit you mention, nor continuity. There seems to be a fair amount of rubble below the eroded crater rim which Opportunity now faces, and I don't know where you see subsidence.


Ahh, they're taking the high road, since the entrance ramp is nearby. That should be interesting. Like Bill, I was assuming they'd at least zip down the vertical exposure to collect better data from some other areas. Hmm, all I can see in the direction of the ramp, besides easy access to the top, are some possible...nope, I promised myself I wouldn't use the "f" word... It should be an interesting trip across the top though, as long as they take a few photos along the way.

That's my bet.
We should know the answer after tosol evening downlink; there is driving activity planned for sol 747.

The structure here tends to be confusing! From the MOLA data we seem to be climbing topographically, which means we have to be climbing stratigraphically if the beds are flat-lying. My "day job" is working with the Pennsylvanian Pottsville Fm in Alabama, which is a coal-bearing deltaic sequence. It is esssentially flat-lying with a gentle regional dip, but local sedimentary structures can make the local dip anything it wants to be. However, if the underlying "Payson Formation" can be correlated with the "Endurance Fm" this will help nail down the the structure and history of this area. This is our current ace-up-the-sleeve and something we should study as close as possible. I wanted Oppy to stop at the first exposure of the dark bedrock that we saw at "The Four Lane" on the North Erebus Rim but the priority then was to get on with the detour around that monster dune complex. Although forward progress is essential we should not pass up an opportunity to collect data. Although Victoria is an important site, we can't be sure it will be reached and we need to collect what we can when we can.

This current location is a bit troublesome to me: the trough reminds me of underground mine subsidence. It might just be a byproduct of desert winds and sand, but spot is spooky to me.

--Bill

I've just brewed this Flash-based application to calculate Martian horizons for those who are interested.

Andy

Nice tool! Thanks Andy.

Very slick.

Bill:

Yes - my thoughts on this spot are less to do with the detailed stratigraphy, which is of course important, than why the rock that isn't there has decided not to be. There's not much in the way of debris below the outcrop (compare it to the talus slope around HP) which suggests that we're not looking at simply some mass-wasting process. I'm beginning to wonder whether there is a localised faulting process at work, perhaps following the lines of weakness created by (very old) frost polygons.

I hope we get a good look at some of the other outcrops!

Bob Shaw

I think the evaporite rocks and cemented aeolian sandstones simply crumble and blow away after millions of years of weathering, which explains the lack of ejecta blocks on all but the freshest craters. Payson is not the pristine rim of a crater, it's the remnant of an old crater after a billion years or more of weathering, scarp retreat etc. The central bowl of Erebus might be closer to the original crater size.

Phil

Just a thought - the fact that we already have drive direction imaging showing a route up onto the top of Payson suggests that they're not going to hang around here and investigate the front of the outcrop

Doug

Scarp retreat is exactly what I think we're seeing at Mogollon and Payson. It's my belief that the original Erebus was only about twice as large as Endurance, and that it struck into the western side of the bowl of an even older, larger crater (Terra Nova) that had already been mostly filled with dunes, evaporite and sediments. (If Terra Nova had been an unfilled crater at the time of the Erebus impact, I would imagine that you wouldn't see such a pronounced east rim on Erebus, which lies roughly on top of what would have been the deepest portion of Terra Nova.)

Because the evaporite and weakly cemented sandstones are rather friable, scarp retreat ensued rather quickly, and continued even as Erebus' own bowl was filled with sand, sediments and evaporite. It probably continues slowly to this day -- Mogollon and Payson might be moving away from the center of Erebus at the rate of a few centimeters every hundred thousand years or so...

Remember, too, that most evaporites *shrink* a tiny bit as they completely dry out (think of the cracking you see in dried-out lakebeds). This process is complicated if the last stages of dessication involve ice as opposed to liquid water. There would be a tendency for an evaporite "cap" on the crater fill to shrink away from the crater rim a bit, encouraging a final subsidence along the rim line.

I think all of those factors are at work here...

-the other Doug

We should know the answer today at 20:35 GMT (assuming the exploratorium is still working at that time).

From me, too: Goodbye Olympia

Last view of this outcrop shows 3 out of the 4 named bedrock regions. Roosevelt is out of sight.

3 targeted outcrops (447 KB):