Is there a current guess as to the initial slope?

We measured some slopes on the far side bays to be in the 16 - 20 degree range as I recall. My guess would be similar sorts of values for this bay.

I hope you're right, Tesh! Then the 162 Navs should show us whether there's an 'exposed coal seam' ( ) down there, and the 342 Navs should show if the valley slopes are "without peril" or not.

Some details on the sol 1116 fault in the latest update:

Aha! The penny drops:
After a wild weekend in Pasadena, it comes as no great surprise (especially if Emily was buying the drinks) that Oppy needed a couple of days to sleep it off. No problemo!
We know how it is.

They deserve a day (or three) of rest. It appears that we'll need to be patient, waiting for that elminus view and the pancam foreground set.

Is there anybosdy down there?...

That image is an old one.
The new ones has a site/drive id "8153".

Watch your step little rover!!!
Click to view attachment Click to view attachment Click to view attachment

A quick autostitched mosaic...

That is REALLY scary!
...and thanks for the correction Tesheiner...

The entry point would not be in bay D1 in your mosaic, but in C5 where there is a nice gentle slope.
Hope they move southwest to the tip of cape C5 (I guess unnamed as it is between CGH and CSV) to get second set of images. I would assume that the name "Valley Without Peril" refers only to bay C5 and not D1.

No doubt. I think D1 was never considered as a possible entry point.
I think too that a move SW is a good one. Half of the bay (C5) is currently hidden behind the tip and if they are still considering it as a possible entry point it would be good to see the whole path down from this side.

> I would assume that the name "Valley Without Peril" refers only to bay C5 and not D1.

I would consider it as a valley with two entrances, "without" and "with" peril.

Edited: Added this two-frame mosaic of Bay C5.
Click to view attachment

The new images allow us to put some actual constraints on the slopes. From the pre-drive sol 1126 navcam, we can say that the upper reaches of the C5 side of VwP is at around 15 degrees. Totally doable.
Click to view attachment
From the 1129 navcam, it's harder to say because we don't have the horizon in the downslope images, but a rough guess, based on Tesheiner's mosaic (did you use 75% reduction?) is 22.5 degrees for the visible portion of the D1 side:
Click to view attachment
There are small errors in these estimates due to navcam distortions and any non-zero elevation of the apparent horizon.

Edit: correcting for actual reduction of 70% (see below) gives 24 degrees for D1.

There would appear to be dark material on the exposed rock in front of the rover. pursumably streak material that has blown out of the crater...

ed

> From the 1129 navcam, it's harder to say because we don't have the horizon in the downslope images

The "normal" navcams (including the horizon) are tilted down at 17º while the downlooking ones are tilted at 30º. This might be helpful.

> (did you use 75% reduction?)

70%

Yeah, that certainly is helpful! 70% instead of 75% reduction means my estimate of the D1 side slope increases to 22.5 degrees * 75/70 = 24.1 degrees.

Taking the centre of the downslope D1 navcam to be -30 degrees elevation, I get a slope of 23.9 degrees.

Of course, those decimal points are meaningless, but two distinct methods now give very close to 24 degrees for D1, so I'd be willing to bet that's very close to the truth.

A few things puzzling my weary brain....

• the dark clear/dusty streak is very clear up ahead - the one we've just passed over (Sols 1123-1126) was virtually invisible at this angle, wasn't it? What's different here?
  
• I'm also puzzled about those patches of bare rock... eg: http://nasa.exploratorium.edu/mars/opportu...53P1964L0M1.JPG
  
  why a bare patch here, and not just ---> over there? Happenstance and randomness?
  
• 25° is within Oppy's 30° slope capability, but I guess that figure is only true for the path straight down the middle of the 'chute'. The angle appears to increase gradually towards the edges (here at least, unlike the more ramp-like ramps.) So if the object is to get up close to the outcrops, this probably isn't the best entry site.

Oh dear, too much Powerpoint hell this month... I'm dreaming in bullet points! %)

BAD QUOTING REMOVED - STOP IT - Doug

the first streak, which loosk in the Tesheiner's overhead map to be somewhat dark, was never quite as dark as the further one.

And if you go back to the SOL 1123 view

and then further back to the SOL 1098 view

the first streak is relatively unnoticeable from the ground, a mere hint, but the second streak has always had very sharp and dark features. its odd why there is such a disparity from the ground vs the overhead views of the darkness of the first streak, maybe its just at the brightness threshold where it becomes an artifact of camera exposure contrast stretching/compression, but im hoping well get a MI view of the dark streak so we can settle once and for all whos camping out in ground truth: the dust-covered vs dust-cleaned campers.

If you look at the MRO orbital imagery, the first dark streak (the one we're sitting on now) is distinctly less dark and has quite a bit fuzzier boundaries than the second streak. Add to that the fact that these are pretty wide features, so you'd expect them to be less noticable when you're sitting on top of them.

If we had a calibrated full 360 navcam mosaic from here I'm sure the streak would be easily noticable.

Check these fresh images from sol 1130:
http://nasa.exploratorium.edu/mars/opportu...cam/2007-03-30/



Edited: Added a 6x1 navcam mosaic.
Click to view attachment

Oba Tesheiner!
That looks great!
There's a path inside the crater, to the left, where Oppy could study the intermediate layers, angle allowing...

"Dear Santa,

Sorry for this late letter, but I have another wish for you.
Could you please tell those guys at JPL that *THIS* is a fantastic place to stop and take a full-color 360º panorama?"

Maybe Tesheiner, but I guess Opportunity will go from here to the tip of Cape St. Vincent for the full color 360 panorama. The images from CSV will complete documenting the Valley Without Peril--then Oppy will drive back and enter Victoria about sol 1145.

YIKES! The rover is close to the edge... They took more risk than I expected, and the rover said, 'Hey, no big deal - I can do it!

That's quite a neat pan, Tesh! Thanks much...

Why do I imagine something like this conversation happening?

When the rover is far away from the streak, the ground goes from light to dark to light in just a degree or two. This makes for a high contrast image. When it is on top of the streak, the same contrast values are spread out over several frames of the navcam. The much more gradual transition gets lost in all the noise of the image. The noise includes actual camera noise, edge darkening in the navcam, and features in the image.

As fredk said, if we had a fully cal'd 360 mosaic, you would see the streak. But it would never be as obvious as it is from a distance.

ed

The streak was never really very distinct from a distance as viewed in earlier SOLs, only the second one is distinct as seen on SOL 1123 and SOL 1098


Yikes!! I can see it now: Oppy careening out of control down the slope, splaying its wheels in futile panic atop a rolling carpet of blueberries!

This just in from Jim Bell:

Today they should be on the second dark streak. After that, back to the rim, to continue the series of views from different headlands. No entry yet. After a few more headlands there will be another full crater pan similar to the full pancam view from Duck Bay. Entry will have to wait.

I just came from his talk at Western where this was described.

Phil

(Lyford... )! A peril beyond price indeed...

It was not as distinct as the far streak, true. But it was easily seen on 1098. By 1123, the angular spread was larger but it was still visible. The progression from 1098 to to-sol demonstrates the fading effect.

In this navcam shot, It is easily seen. here we're looking right at but you would never know it by this shot.

ed

yeah, even given the contrast differences between all the images, i think you're absolutely right.

This would suggest that its the blueberries themselves, and not the dust between them, that is responsible for the dark streaks (since as Oppy gets closer, the light soil is progressively revealed between the bloobs, lightening the streak).

So what then could darkening the blueberries in this pattern? maybe its the removal of light dust coating by the winds or vortices propogating out of the crater? which means maybe the clean-streak camp has got it right after all...

looking like streaks of dark dust blowing out of the crater with an obvious source in the dark eroding cliffs, im no longer sure what camp i want to be in anymore... or maybe start up a new camp saying they are darkened from interacting with some humidity as it is blown up and out of the crater by the prevailing winds. far-fetched?

That's good news. I like the idea of traveling further around. Did he say anything to shed light on the genesis of the dark swaths? I'm not sure what is going on, but as has been noted previously, the ground and the berries look cleaner to me.

Just remember this Oppy. Tomorrow is April Fools Day and we all don't want you doing any crazy tricks that close to the edge. No power slides down the slopes and

-----> DON'T JUMP!!! DON'T JUMP!!! <-----

Click to view attachment

DANGER, OPPY... DANGER!!!!!!

Tomorrow, April 1st, *IS* a driving sol.
I just hope they won't confuse forward with backwards ...

Good point, Bobby. Thanks for the warning.

There are dark streaks trailing downwind, towards the left, from what I'm guessing are blueberries at the bottom centre to right of this pancam frame:
http://qt.exploratorium.edu/mars/opportuni...90P2395L2M1.JPG
To me that suggests the dark stuff is a deposit, rather than the result of clearing off light dust.

I thought the dark streaks were the product of wind processes, at first. I thought that for a very long time. Yet, I wasn't sure how this was possible. Wouldn't the wind processes follow the patterns observed at Gusev Crater? This dark streak pattern at Victoria does not make sense given known wind process at Mars.

Now that we are much closer to the dark streaks and they seem to be made of increased numbers of blueberries that are fairly clean, I'm changing my opinion about their origin. I'm now thinking that there is some residual groundwater relatively near the surface. That groundwater is continuing to interact (in a minor way) with the atmosphere in some sort of capillary action within the soil. This minute amount of water would carry some minerals from deep below. In other words, the blueberries might be created close to the surface.

The wind action tends to bury the blueberries in dust. In areas where groundwater persists closer to the surface, you would get dark streaks. The reason the streaks are not dendric in structure is becasue they are primarily created from the capillary action and not directly from the underground stream (it's too deep).

I think this capillary action hypothesis is something to think about and possibly persue.

Not really -- the markings at Gusev are caused primarily by dust devils. There have been *zero* indications of dust devil activity at Meridiani (at least anywhere close to Oppy's landing site).

The dust-devil-track type of markings aren't even the most common type of visible wind streak on Mars. The most common type is a clean-sweep dark trail in the lee of crater rims. Orbital observations have *strongly* indicated that these dark streaks are places where wind turbulence has cleaned off bright dust, leaving the dark streaks.

So, one of the reasons why a lot of people have championed the clean-sweep theory for the streaks coming out of Victoria is that this *would* be most like the known wind processes on Mars.

-the other Doug

The major problem is that those other streak features you are talking about generally occur on steep grades. These streaks are not. The dark material only extends into Victoria crater and piles up near the northern cliffs. I don't see the winds being strong enough to pick up the dark material on the north side Victoria and depositing it on top; more likely it would happen in the exact opposite direction. If a regional wind was strong enough to do that, then it would likely disperse the dark material throughout the Victoria area and not just in those finger like bands on the one side.

There is also the problem that the streaks are primarily made up of concentrated blueberries, not dust. Blueberries are NOT going to be blown out of the crater unless it was during the initial impact. However, dust from the decomposition of blueberries could easily be blown into the crater from the north side and pile up just below the cliffs.

I don't understand your point. From my point of view the most likely explanation is that these dark streaks are areas that are partially cleaned of the extremely fine light coloured dust layer so that the underlying material (which is darker) is exposed. This happens because wind is accelerated (and probably more turbulant) as it is funneled by the bay/cape scalloping and can therefore carry (and lift) dust fines more effectively.

More Blueberries may be obvious in the dark streak areas but that would be simply because they are not covered with the same surface dust layer as elsewhere.

They start to take Pano pictures!
This is stunning view from Sol1131, R2 filter (look to the rolling rocks trails):

Yeah, that's going to be a beatiful mosaic.
It's 14x2 on filters L257R2.

Just discovered some artifacts in my previous stitch (ghosts due to autostitch).
So I re-made using Left pictures (only top row) and making a colorization...

Beautiful set of crisscrossing rolling boulder trails at the bottom of this image.

Man, I'd really like to know what time scales we're talking about here. When did those guys roll? How often do chunks this big come off the cliffs? Understandably rhetorical.

The problem with that is the piling up of dark material below the cliffs. The transport of the light dust around the blueberries does not explain this. Perhaps a closer look at that dark material inside the crater will help solve the mystery.

I see the two as being slightly different but the dark nature of both is probably because we can see the blueberries and other harder\darker materials in both these areas. Around the cliffs it is likely that sorting processes will develop a higher density of the concretions at the bases as the cliffs are eroded back over the eons. I accept though that this is simply my speculation in both cases.

We should have some real data to put an end to the speculation soon though in any case.

I wrote above that we have dark deposits in the lee of blueberries here. At the bottom of this pancam view we can see sizable collections of dark dust in the lee of some small rocks. Again, doesn't this suggest the darkness is a deposit rather than a removal of light material?

I agree. That's why I don't think the primary source of these streaks is wind related. Wind has only slightly modified them.