Wow! If I live to be a hundred, I'll never understand why we've sailed right on past the Beacon toward "Boat Ramp". I agree that the deepest exposures are the most important, but Beacon is the highest! It's sitting right there waiting for us. It's the top of the section. Whether it's composed of impact breccia or undisturbed laminated evaporite determines whether Victoria formed after or before the deposition of the upper Planitia Meridiani. I can't believe that is a trivial issue. It is a fundamental fact of Victoria's history.

And so Oppy drives on, away from Beacon and towards the next Cape...

VERY interesting feature coming into view now, a tall "stack" of rock on the end of the next Cape, a kind of martian "Old Man of Hoy"...

Click to view attachment

Not an exact comparison, I know - the "Old Man of Hoy" stack is totally detached from its cliff - but the best I can do at 7am, 4 hrs before I leave for a week's holiday in Spain. So, have fun all, say hi to the next Cape for me, and I'll look forward to lots of gorgeous pans by you all of "Hoy" when I return...

I'm wondering if they will name it another cape or actually consider as Cape St. Mary the whole structure the rover is now on.

> 4 hrs before I leave for a week's holiday in Spain.

Enjoy it Stu! And I hope the weather would be better then the last few days (raining).
I'm now 8h before I leave for a week's *work* in Germany.

It is a new Cape isn't it? Going by the latest map... Isn't "Hoy" on the end of the next Cape clockwise...?


Click to view attachment

I would have thought they would drive to the other side of C St M first - to observe the outcrop on the near side of the next cape and THEN drive around the next bay onto that next cape from which to observe the northern outcrop of C St M and the Southern outcrop of the next Cape.

Enjoy Spain Stu

Doug

Without access to information such as TES or the MB and APXS work done recently, it is hard if not impossible to understand why they might or might not have done something you thought they should.

Doug

Hmmm... I'm not sure now.... Just been looking at the navcams...

Click to view attachment


... and I feel a bit confused. If I look at it, I can almost convince myself that the "Hoy" feature does appear to be part of Cape St Mary... especially if that is the wide "ramp" over yonder, just over the shoulder of "Hoy"..?

Oh well, I'm sure you'll have it figured out when I get back.

Edit: no, I'm sticking with my original idea, I think it is a feature on "the next Cape" along. Going with first impression.

Shutting up now.

I think "Hoy" is here:

Click to view attachment

Phil

"Hoy" = Cape B1

Jame's labeled map

Hoy is more likely at the end of the c1-c2 cape. There are two capes in the image and a bay between them barely visible.

I hope they're careful - it looks like Opportunity's headed toward some prime spots for dust deposition.

It looks that way to me too. That would mean we're only seeing the top of the B cape cliffs so far and they go some way further down. The 'Old Man of Hoy' might just be the tallest vertical feature in Victoria. Unfortunately Magellan didn't sail past Orkney (or Cape Horn, which would have been an ideal official name).

I agree with MarkL and ngunn. We're seeing things heavily foreshortened in that direction, so looking slightly to the right means seeing capes much farther away. Here's our and the orbital views matched up:
Click to view attachment
Click to view attachment
Bay B3 is completely hidden from view currently.

That's right. I didn't look far enough. Here's a comparison of the image at the top of this thread, after using the perspective tool in Photoshop, with the HIRISE image.

Phil

Click to view attachment

Shaka: I'll have to admit that I too was a bit surprised that they left the area so quickly, but it is true that they have a lot more spectral information on the rocks than we do at this point. I think we might be able to get a clue though, from the MIs taken of the RAT hole on Cape Verde. Granted, CSM is higher stratigraphically, but not that much. The MIs displayed several large berries embedded in the rock and shaved by the RAT. They are pretty confident in their model of these concretions having formed in sediment saturated by ground water, or what is usually called the phreatic zone. On the trip south Opportunity climbed stratigraphically and observed no berries and micro-berries at the highest points, which is consistent with that model.

The fact that they discovered large, embedded concretions in the rock here might suggest that these rocks came from the section that we have already seen. I must point out a serious flaw in this argument before someone else does. You would expect the surface rocks there to be ejecta, so they likely were derived from deeper layers. But now that I think about it, perhaps a better argument fro leaving would be that it appears that CSM is also mantled in ejecta, so what is the point of wasting time there? Better to move on and learn more about deeper, intact layers.
Click to view attachment
Jeff7: Some of us think those dark streaks were formed by the removal of light colored dust rather than dark dust deposition. So, it may be a good place to go for Opportunity's solar panels. I hope we can observe something on the soil as Opportunity passes bay B1, to allow us to determine whether the streaks are due to erosion or deposition.

As long as I am going off topic, here is the drive direction panorama from sol 1009, as I was able to stitch it.
Click to view attachment

As for the "dark" streaks this zoom of the high resolution colour Victoria crater TIF file suggests the dark material has moved come from / been blown from Victoria crater and overlayered lighter material. Victoria crater is below and to the right (about 5 o'clock) of these small craters.

Click to view attachment

This streak debate seems to have legs and might become the next near-rim, far-rim brouhaha! Either way there could be wind blasting through there.

Yes, that's fascinating. Those craters could be candidates for a visit later on. I've often wondered about the petrified figure at the southeast rim. A lost sightseer perhaps?

This is true, of course, Tom, but why not grab the very top of the section when it's sitting there waiting for you to RAT it. And we have risk-free access to the exposed edge of the layer, as well as the top, without having to reach over the brink and risk a tumble down to the dunes. If the edge reveals laminae, and there is no discontinuity with the underlying layers, we have strong evidence that the beacon is in situ, and therefore points directly at an ancient (Noachian/Hesperian) formation of Victoria, followed by burial and recent exhumation.


But if the evaporite is in situ, then it indicates that ground water existed both below and above the berry-free strata.

But Tom, those of us in the "Ancient Victoria" school of thought, don't believe that we are seeing, driving over, or ratting Victoria's ejecta. We hold that ejecta is nowhere to be seen. What we are seeing is sandstone that roofed over Victoria back in the Noachian/Hesperian, was subsequently indurated and leached by ground water to produce concretions, and finally eroded and collapsed.

I am frantically awaiting close-up views of the uppermost exposures in the capes to see if they are primarily intact, in situ, more or less horizontal sandstones. The latest pancam of "Hoy" looks remarkably in situ right to the top. If close examination confirms this all around Vikky, then I will hold my hypothesis to be supported. I cannot emphasize too strongly that a hypervelocity impact shatters the target rocks near the crater, transforms some into exotic forms, hurls them high into the air and deposits them around the crater with a more or less random orientation of chunks (OK, clasts) in an impact breccia. We saw some of this around Beagle, though that was such a tiny crater that regular impact models may apply imperfectly.
I have not yet seen anything around Victoria that I would call impact breccia. Close-up views may reveal it, if we ever get any. Hence my disappointment when Beacon was bypassed.

I agree with you on this. I don't see any source of dark material down in Vikky. The only dark things in this area are the concretions, perhaps, and the basalt sand grains when they are cleaned of dust. It depends upon lighting and viewing angles, of course, but in general, what looks darker on Mars is more dust-free.

Yeah, I'll let other, more tidy minds decide whether to leave these posts here, or put them in the stratigraphy thread.

There are dark dunes in the eastern quadrant of the crater that could be the source of the plumes of (relatively) dark dust. The colour doesn't match the average colour of the mantle over this region so I'm on the dust plume side of the debate.

I would reply, Mark, that those dunes have been swept free of light dust by the same winds that funnel up through the bays to sweep the annulus beyond. I think it's unlikely, and unparsimonious, to postulate a source of dark mineral existing in Victoria, other than the basalt sands and blueberries that are everywhere else.
Of course anything is possible, but the likelihood is that the whole deposit making up the Planitia Meridiani is about 800 meters of more or less uniform, laminated basalt sandstone, more or less indurated by sulfates, and containing varying concentrations of hematite concretions. Victoria's formation almost certainly did not excavate below these sandstones, and so I would not bet the farm that we will find anything else in the crater.
One can hope, but...

P.S. "Cry, Havoc!, and let slip the Dogs..." Click to view attachment

Err, not Phobos and Deimos - It's the sun.

Rats. I so wanted it to be.
So what's the little oval to lower left? Nothing but an artifact? Why can't modern science invent an imaging device that is free of artifacts? Hell, if they can put a man on the moon....

Yep, an artifact, go and look at the right eye image taken at the same time, it's not there in that one. It's always worth checking the filter for images like this, 8 (in either eye) is the solar filter and will never be of anything except the sun.

This image is part of an observation of the atmospheric tau at sunset and you can actually see the horizon across the image.

James

If I had a nickel for every time someone made that mistake in this forum... I'd have several nickels.

I thought it was an artifact of parallax that Diemos wasn't there!

Good tip! Actually I haven't managed to penetrate the MER image labels much farther than the time stamp, without losing my place.

Hi Mark,

I suggest the dark plume material may be originating from inside the crater as suggested in this marked up image:

Click to view attachment

There are two other clearly visible spots around the rim where darker material is also seen:

Click to view attachment

Victoria may have more untold secrets to learn

The usual interpretation of dark streaks etc. like these is not that they are dark material, but that they are places where the regular dark surface of Mars is freshly exposed because bright dust has been removed. The orange-pink dust in the sky of Mars is always settling onto the surface - and constantly replenished by dust devils and occasional large dust storms. So the surface is usually covered with dust as a matter or course.

Dust devil tracks - the DD removes bright dust leaving a dark streak.

Steep slope streaks - a small landslide or "dust avalanche" sliding down the slope causes enough motion to expose darker stuff under the surface dust layer.

So here in Victoria, the streaks and patches in the post above are caused by small downslope movements, recent small landslides etc. They are not patches of dark material - everything is dark everywhere. But most of it has a veneer of bright dust.

And the plumes are places where the dust is removed by wind focussed up the "ramps" - and made more turbulent in the process. The crater higher up the posts does indeed look as if darker dust was deposited over most of it, leaving bright dust exposed only in the sheltered areas. But the reality is still probably the other way around. The wind blows bright dust away everywhere except where it's sheltered.

I'm not saying it couldn't occasionally work the other way, but this is the generally accepted explanation. If it's true that in some areas dark dust is being blown around, keeping it from becoming intimately mixed with the bright dust would be very tricky. Incidentally, dark sand dunes are seen in some areas, but sand grains would be hard to get out of a deep depression. That's another issue.

Phil

Bonneville definitely had dark matterial that was forming dunes on the crater floor. And it was blowing up and over the crater rim to leave a dark streak on the plains down wind... It seems plausible to me that there could be a layer of darker matterial that is exposed in the wall of Victoria. That this matterial is eroding and being swept up and out of the crater.

I agree with Phil's points. I think our position represents one pole of a "streak hypothesis", wherein the dark streaks are formed by cleaning winds. The opposing hypothesis implies that the streaks are "dirtied" by some unusually dark, exotic material eroded from the walls of the crater and scattered across the annulus. Presumably this debate will be soon settled by MIs of the surface outside and inside the plumes.
We could call these two schools of thought, the "Clean Streakers" and the "Dirty Streakers"!
I'm sure Ustrax could devise some appropriate mascots.
Who wants to sign up?

I looked back, but I don't see that at Bonneville. From orbit, nothing looks like it's blowing out. From the rim, the dark streaks crossing Bonnevile look like dust devil tracks to me. The one area that might be different is an area of dark dunes under the west wall, but other dunes are lighter, suggesting to me another DD track, or possibly a patch of dark sand like Eldorado, which we do see getting trapped in certain topographic situations.

Phil

Good one Shaka. Much rather be a dirty streaker!

I might go for a clean streak though, if the special mechanism that makes it appear as though dust is coming out of the bays is explained by repeated cleaning events. Well behaved dust devils perhaps? Also, in Meridiani the dust is dark and the outcrops are light, unlike much of the rest of Mars.

Prometheus, that's it!

I really have to think Phil is right, that the dark areas have been windswept "clean" of the ubiquitous bright dust. Which means that Oppy ought to be able to get a nice panel-cleaning by placing herself in the path of those winds!

-the other Doug

But Shaka, I contend that we have seen several cross sections of capes relatively close-up at this point, including CSM. All of them appeared to be mantled by a jumbled layer of blocks in random orientations. That looks like an impact breccia to me. The stable places that have endured long periods of erosion seem to display flat faces eroded by wind, and the less stable areas that have seen mass wasting more recently display the boulders in various stages of erosion. I don't see anything like in-place bedding at the surface on any of the capes, so far.

I know that in the past I had argued that Victoria wasn't all that ancient, but I have since modified my view and have mentioned that. I think it is fairly old, but I am not certain how old. I am still looking for evidence of the hypothesized ancient fill that was eroded, undercut, and which subsequently collapsed. I am not convinced I see it in the close-ups we have so far. If I had to make a guess from our current selection of close-up samples, I'd guess the original crater was smaller than the current hole.

I agree with him too, but...Oh, no. Let's not start another polarizing argument with team badges. We won't have the measurements needed to decide until Opportunity gets to a dark streak, and even then we won't have the calibrated spectral information. From my point of view, the simplest explanation is that the well observed and globally distributed light dust has been removed here, as it has on all of the rougher, upper slopes of this crater...

I hope this leaves clear what is my position about this childish creation of teams to discuss such important subjects...

I think I just heard Doug breath a deep sigh of relief!

Phil seemed to sum up what I think the streaks are, so I suppose I'm more of a clean-streaker. That seems alot more comfy than being a fence-sitting streaker...

I'm joining the 'clean' streakers. But Oppy should be careful approaching the cleaned area, there may be dust buildup surrounding the cleaned areas.

I wonder if the winds that create the cleaned streaks are seasonal or persistent?

El Dorado was a dark spot though, and it was a prime deposition spot.


Either way, I imagine we'll find out soon enough what's going on at those streaks.

I am so on that bandwagon Ustrax!

As with Spirit's local where winds develop in the summer, I'd expect similar seasonal effects at Victoria too.

Since the wind 'tracks' are relatively short (and wider) by comparison to many seen at craters in Gusev, it appears that the size and strength of the whirlwinds that form in Vicky's bowl are probably shorter-termed, somewhat weaker, and less tightly concentrated than those observed at Gusev.

Not a long drive sol 1012 but enough to give a nice long baseline with the 1009 images in the direction of the Hoy cliff feature. This makes it a lot easier to make out where one cape ends and the next one farther back begins in the images:
Click to view attachment
I prefer the cross-eyed version:
Click to view attachment
Some distortion here since movement wasn't perpendicular to the line of sight, and pretty serious lighting differences.

I'm beginning to think that Victoria with its "capes and bays" looks more and more like a sinkhole rather than a crater.

See here:

http://ga.water.usgs.gov/edu/earthgwsinkholes.html

The first image at the above link looks nearly identical to the "bays" that we see in Victoria.

I'm not worried about dust build up on Oppy. Compared to Spirit she seems to have better luck finding cleaning events. Compare the sundials of the two rovers.
Click to view attachment

I think it's a bit of both: Impact - fluidisation of substratum - undermining and irregular collapse of rim - wasting by sublimation from the fluidised floor material - partial infill and some reshaping of rim by aeolian processes. This is an old idea and we have seen much since it was first aired (2004 if not before), including the paper on the burial and exhumation theory in print, another paper on a possible new easy-melt Martian mineral, HiRise and all the Rover imagery so far. I haven't seen anything yet that makes me want to switch my bet.

The panoramic view in the drive direction on Sol 1012.

Taken with the L0 Navcam.

jvandriel

Here is the Pancam L2 panoramic view in the same direction.

Taken on Sol 1012.

jvandriel

Navcams after driving on sol 1014 are available.

http://nasa.exploratorium.edu/mars/opportu...cam/2006-12-01/

Some fence-sitting by Steve Squyres...

""It could be dark sand that has been blown out of the crater," Squyres suggested. "Alternatively, it could be places where there has been selective stripping of fine-grained dust by locally enhanced winds," he pointed out. The MER team is planning a campaign to study one of these streaks, he said, once Opportunity gets over to that area."

I think the presence of El Dorado (Ultrea)-like dark ripples below the crater rim
where the dark steaks occur argues for the dark sand hypothesis.

While I'm still in the clean-sweep camp. The dark sand within Victoria isn't, to my eye, as dark as the streaked surface.

Of course, I'm prepared to be proven wrong...

-the other Doug