Yes, I have to agree, CR. True, the drifts have been friendlier around here but this appears to be a Jammerbugt-size drift, not like the little puppies we've been crossing. Maybe the southward trough is okay, but it looks a bit scarey to me in the anagylph views. I'll be very interested to see what they do. If they go through the south trough, I'll call that a daring move. But they've done moves before that I considered daring.

"Yikes" is an understatement, sir. The rover has done positioned herself betwixt the dog and the fire hydrant. I thought Oppy had driven to a light-toned outcrop, but it does seem to be light-toned sand, which tends towards fluffiness. We may be able to drive across it to that cobble-patch shown in Tesheiner's suggested path, but my intuition-voice keeps jabbering...

We'll see. I have faith in our drivers...

--Bill

Did anybody notice the mottled soil in this one? Have we seen this kind of thing before? I don't remember.

I'm curious if the far fringes of the ejecta blanket are mixed in with the dune material. At first glance, it doesn't look that way, but if we were able to be there in person, we'd try to do a profile to see the timing of Beagle/Corner Crater and the dune making events. If there's any "dune material" under any Beagle/Corner Crater ejecta, it might help considerably with timing events and perhaps help out with dune causing events.

As it is, Oppy is limited in power, abilities and perhaps timing so perhaps a closeup look at one or two of the locally taller dune features is all there's time for.

This look like a bedrock under a very thin layer of dust/sand

Here and now I don't know, but I WOULD expect some microscopic examination of the surface soon since things are starting to change.

That caught my eye too. My first thought was "patterened ground", a soil structure that develops on permafrost. But, of course, that's my terrestrial bias. It does appear as if there is some process that is separating the soil into those little mosaics.
It's a similar pattern as the fractured rocks that we've seen exposed between the drifts, but it looks as if the soil pretty thick here.

Mike, Gray--

This _is_ very strange. The pattern does look like slabs of evaporite complete with the "dessication cracks", but covered with a thin layer of dust. This might be a situation where there is a jumble of evaporite slabs emplaced as ejecta from Beagle or Victoria craters. Since these craters are quite recent, this ejecta is in the process of weathering down.

Rather like what Aldo at marsgeo.com describes at Endurance:

http://www.marsgeo.com/Opportunity/Sequence.htm

Attached is an enhanced clip of the image that mhoward mentioned.

Tread lightly, young Rover. There may be voids below...

--Bill

Hey, I think you're right!
Look at this elaboration, made in order to increase these features through assigning different color channels to different scale features:
Click to view attachment
I hope this pavement is really hard rock, so Oppy can go safely go ahead without to try another route!

Edit: however, the dunes few meters ahead seems very sandy and thick!

There certainly are a lot of back seat drivers today. Is there room for all of you?

Are we there YET!?!?
Are we there YET!?!?
Are we there YET!?!?

Attached is a pan assembled from the L2 images from Exploratorium with today's date (I think Sol 871). No fancy anti-vignetting, just an autostitch mosaic ... with distances to many features noted (distances calculated with AlgorimancerPG - in meters). I wanted to get a sense of scale.
Click to view attachment

You'll need to zoom-in the read the text. If that Jpeg is too fuzzy to read, here's a crisp giant BMP version (12 megs):
http://www.clarkandersen.com/OppyPano20060707.bmp

Or a small (700K) but high quality Jpeg2000 version for those who can deal with it:
http://www.clarkandersen.com/OppyPano20060707.jp2

The Beagle near/far rim labels are somewhat speculative, but loosely in agreement with range estimates from the current Sol 871 Route Map position (per Tesheiner).
http://www.unmannedspaceflight.com/index.p...ost&id=6587

The photogrammetric distances have too much error to be very useful much beyond 200 meters. I would estimate that the Victoria ejecta blanket commences at about 140 meters.

Just thought I'd share

Bill:

It's too regular for ejecta at such a scale.

And it's far too small for traditional patterned ground, which is based on slow (annual rather than diurnal) movements of ice and rock and which has scales measured in metres to tens of metres.

But...

...if we're at the edge of the Victoria ejecta blanket, are we seeing what amount to 'cells' within a now-dessicated fluidised flow? Imagine the initial slurry of muddy debris, foillowed by pretty rapid freezing. Then, the volatiles vanish, things contract, and... ...voila!

There's probably something about the physics of packing rough materials there too. If that's the case, forget about voids!

We may be seeing a proper fossil ejecta blanket, or at least a slice through one, made of the remnants of a volatile-rich slurry.

Bob Shaw

Back seat driving implies that the driver is listening, or at least can hear you. We know that is not the case.

No, we simply want to be able to say, "See... Told ya so", if Oppy should get embedded again. I think there might also be a feeling that if enough people predict failure, success is guaranteed, which is really what we all want.

Brian

Neat! You could have used this one as a base, though.

I'm not backseat driving. I'm just, er... wondering where the heck we're going? Okay, maybe I'm backseat driving.

On the other hand, it's been a *very* long trip and I think we're excited to finally be getting somewhere. (I hope.)

Are we there yet?? Are we there yet??

Whew, Bob, I don't know what we're seeing here. After I posted that previous message (which originally said just Beagle ejecta) I edited it to include Victoria's blanket, too, which, from the MOC images, looks more/most likely.

This will be a changeable locale, so let's tread lightly. It'd be the ultimate bummer to get mired down when knockin' on heaven's door...

--Bill

Yes, it's been a *very* long trip, it was amazing to follow each phase and we all are excited to be close to "final" target (below the updated odometry plot).
However...
Cannot avoid to think that 8Km is a journey that a man can easily walk in a couple of hours... to me, is disappointing to think that an astronaut (or a very fast rover) could accomplish most of the overall Opportunity achievements in a single Sol (apart mossbauer integrations, obviously).
I do not want to despise this great succesfull mission (I still a MER fan!) but this help me to mantain a contact with reality and can stimulate thinking what we could improve in future missions.
Perhaps a little bit OT here, but I would like to know other's comments.

I think it's a fascinating question which I have lots of opinions about... but that this is UNmannedSpaceflight... should be another topic, if not a forum of it's own?

Even Squyres is on record as saying that it takes the rover a day to do what it takes a person 30 seconds, and that the total Spirit expedition ( to around the summit time ) was little more than a weekends work for a geologist

The whole argument is moot. We currently have rovers. We do not have the option for people. We have rovers that were supposed to cost around $4M per sol and cover about 600m and have ended up being less than $500K per sol and cover 10x that range. Can't argue with that. In terms of value for money, it's hard to imagine any way of beating that, wheel tracks, footprints or otherwise.

Doug

Click to view attachment

Yep, that would have been an improvement Sorry, hadn't noticed it. Much better quality.

Thanks for the informative graph dilo, what really jumped out at me was how much the rate of driving changed from before and after purgatory dune. They have become much more conservative in their driving..... and rightly so.

Click to view attachment

I just noticed there is a lovely small crater visible at 170 degrees azimuth - visible on the map, too. It's easiest to see the crater shape in the anaglyph (no complaints about the anaglyph please - if you don't like it, do your own ). Perhaps not worth a visit, but pretty. If we drive south from Sol 871, we'll be almost on top of it. It's 53 meters away according to algorimancer's work.

Depending on how much water/ice the evaporite unit contained when Victoria was impacted, this "boundary unit" could have been a fluid splat if wet or a jumble of rubble of dry. Of course, it could simply be an erosional feature on the evaporite surface adjacent to the ejecta apron and not directly connected to the impact, but we'll see what it does. Hopefully, we'll walk away with some more puzzle-pieces in our bag.

--Bill

I was wondering what that ledge-like feature was. At the same time, I was seeing that crater on the overhead view and wondering why I wasn't seeing it yet in the panorama. Now that you mention it, the near rim is only 39 meters away. Estimating the true far rim as closer to 54 meters, that makes it about 5 meters across (+/- 1.5 meters). Cool Oppy could be there in one or two drives. Per the overhead view there's a smaller crater that should be visible just to the right of Beagle, too. Unfortunately at that distance its diameter falls within the range error bar :/

It certainly has the look of a fluid splat. I occurs to me that, with the evaporite unit as a thin hard shell over the underlying loose (or wet) basalt sand, impact into it would be similar to dropping a rock into a pond covered by a thin layer of ice. Rather a lot of the impact energy might have been contained below the evaporite layer (picture it ballooning a bit near the impact, with some radial fractures, then collapsing again). This may have been discussed elsewhere already. This may explain why there is apparenly so little relief visible in the rim of Victoria.

Actually, Alan, I think that instead of saying "Here There Be Dragons," it may be more appropriate to say "Here They Drag Beacons"...



-the other Doug

Okay mhoward, you've inspired me to go back and do some more measurements and feature identification in the panorama, correlating it with the overhead view.

Just to have something to refer to, I've given the nearby craters some Greek identifiers, in order of distance. The nearest crater, pointed-out by mhoward, is Alpha. The small crater to the right of Beagle is Beta. Moving out across Vicky's ejecta, we next encounter Gamma and Delta, both seen behind Alpha's rim, Delta being more prominant. Finally Epsilon is closest to Victoria, seen a bit to the right of Beta. See the overhead view here:

Click to view attachment

Continuing in the next post...

And here is the revised panorama, with the craters outlined and labeled in green.

Click to view attachment

I used ImageJ and Tesheiner's Sol 871 route map to find the angles spanned by the craters as seen from the current position, as well as the angles between the craters, and used that information to identify the craters as seen in the panorama. I was surprised to find that Beta was easily identifiable, and Beagle was smaller than I'd expected (spanning about the same as Alpha, from this distance). I'm not 100% confident of the exact boundaries of many of these craters, but reasonably confident that the features I've outlined are indeed what they seem to be

Incidentally, Beagle, Delta, and Epsilon ought to be adequate landmarks to trigonometrically navigate across Vicky's ejecta with fair precision.

This really shows quite clearly how, to the right, we have the choppy sea of dunes, whereas the apron to the left looks much more manageable for driving. I think and hope the way to Victoria will be a breeze.

As for other small craters: let's focus on the big prize guys!

You see, that's another problem with naming the crater Beagle - it's just one letter from being confused with Eagle.

Fixed it. Not the first time I've made that mistake.

Note that only about 1/3 of Beagle is visible in the 871 image (look at the 870 images). There is a LOT more of Beagle Crater off the edge of the mosaic than your ellipse implies.



Yup, you made it on the image itself as well.

James

That's right; you can see the whole thing in this combined Navcam and Pancam view.

Hehe! Good observation, Doug. I, for one, tried like hell to drag that heavy SOB over to the far rim. For the record, it has for some time now appeared to be an inescapable fact that it is firmly embedded on the near rim, and no one short of King Arthur, is likely to remove it from that place.

Sol 873 images are on the net.

Mmm, end-of-drive due to excessive slippage?
fhaz: http://qt.exploratorium.edu/mars/opportuni...5TP1211R0M1.JPG
rhaz: http://qt.exploratorium.edu/mars/opportuni...5TP1311L0M1.JPG



Edited: Here is previous site's rear hazcam for comparision.

Careful now, Oppy! Careful!
http://qt.exploratorium.edu/mars/opportuni...5TP1311R0M1.JPG

Front wheels not embeddes this time though...

Click to view attachment

Again they get dug down when they try to do a turn on top of the dunes!

The drive-direction wheels are still sitting on top of the soil.... that's a good sign, at least.

Looks like the "back" end broke out a few times getting to our current position, though. Rather like we're on a sideslope -- but it really doesn't look like a sideslope in the images.

I'm not real comfortable with this light-sand box we find ourselves in...

-the other Doug

Well, at least this time the driving seems to be aborted due to slip-checks; that's how I read the motion info from the tracking web (2.5m)

Maybe they were just testing the dune to see if they could drive over it.

Yeah, looks aborted to me. But I'm still amazed at how far they tried to drive, given how dangerous this ripple looked!

Should be able to back out in one sol though I guess.

James

Hopefully they were testing the dune and will back out before too late. The light-toned sand is hazardous because it indicates loose sand. The light tone is an "ochre", reddish color and appears to be derived from weathering of the evaporite. As such, it is a very light-weight windblown material and suggests recent, uncompacted, non-indurated sand that is "fluffy" and does not bear the vehicle weight well.

Be cautious, young rover...

--Bill

I know that the IDD can't produce a lot of pressure, but might it provide enough to cause a suspect ripple's crust to break? Sort of a way of testing the water - put down the RAT maybe and press down as hard as it is able to. If the crust breaks, move on. If not, move ahead cautiosly.
Its design might serve to concentrate the limited force of the IDD arm - it's got those two semi-circle things on either side, with little knobs. They contact the ground first. That'd concentrate the force of the arm right onto those little knobs, enhancing any crust-breaking power it might have.


Other idea for dune-driving - a half-meter at a time. If the crust breaks, you only dig in a half-meter's worth. If not, then it might be strong enough to hold the rover's weight overnight until the drivers have a look at the position the next day.

Looks like the back seat drivers can say "I told you so"

Mmm, not to back seat drive or anything, but... perhaps it's time to just drive around the thing?



That's the view northeastish. Seems like at about 30 degrees azimuth (far left) the drift just kind of peters out to nothing.

Here's the pancam mosaic from Sol 783:



(Note the feature we decided was "Rim of Really Big Crater" on the horizon dead center.)

Nice mosaic mhoward. Maybe they drove up this dune for the view of the area around Beagle Crater.

And if the arm breaks?

Better to do as they do - set tight slip-check constraints.

Doug

http://nasa.exploratorium.edu/mars/opportu...5TP1311R0M1.JPG

I think this shot shows it as well. Roughly east from their sol 871 position? I would like to see them back up and head across those nice, low ripples onto the start of the parking lot sitting so tantalizingly close in your shot.

Brian