This is great, James! It's basically the sort of picture I was expecting. If you look at the bays you and I have measured on the orbital image, the "longer" bays (ie those that extend farther away from the centre of VC) are less steep.

As others have just written, for this reason I'd expect Duck Bay to be one of the least steep. (Actually, I think B1 might be even a bit less steep.)

However, recall that the near rim is considerably higher than the far, and also recall the jpl 3D model animation which strongly suggests that the slope inside the near rim is quite a bit steeper than the slope inside the far rim. We can't be sure yet that Duck Bay or B1 will be traversable. Edit: I see Doug just scooped me on this point!

As far as circumnavigation goes, I agree with Doug that it would be easy given the mobility here. However, I suspect that the lure of deep strata will be too tempting and that if (I think it's likely) Duck or B1 are deemed enterable then they will go in fairly quickly. Recall that Endurance could have been easily circumnavigated but never was.

However, as it's still winter, entering at Duck or B1 is not ideal in terms of having the rover tilted towards the sun. But as spring approaches it may not matter much anyway.

Remember, the main purpose of going to Victoria is to examine the rock layers at the BOTTEM of the crater, you know, actually driving down there and sticking the arm on the layers.

It remains to be seen how deep the lowest intact layers are -- and how easy it would be to get to them. Remember, they gave up trying to get to the upper reaches of the mega ripples in Endurance and they were just a few feet away. Opportunity never got more than halfway to the bottom of Endurance.

Even if The inside of Victoria is Opportunity's last stop, I would say it would take at least a year to explore the "safe" areas before what can be learned there is tapped out and the decision needs to be made: leave the crater or attempt exploration of desireable targets in more risky parts of Victoria.

Sorry, did I misunderstood what you wrote to me ?





OK, it's a forgery but it COULD have been true

You can see in detail about the attack plan in Victoria Crater at the space.com

Des Marais said that there are important discussions to take place over the next few months: Is there enough science value by driving into Victoria Crater? If so, is that research of first-rate importance if rover handlers can’t wheel Opportunity back out?

If it is so, it would be terrific!

Rodolfo

Doug Ellison:
I agree with all those reasons, and more. The only way we will get a good analysis of the stratigraphy and lithology is to look at the exposed outcrops in the Capes from from both sides, full filter set images, varied lighting and with the miniTES. Remember, we are looking for lateral changes in the evaporite over the crater diameter as well as point-to-point differences. Although Oppy could try to enter the crater in a Bay to get a close look at the layers, this might be risky so it would be best done after the circum-traverse. It would be good data, but only collected as a "phase 2" effort. I'm not sure that any good would come of trying to get to the bottom of the "talus pile" between the rim and the central dunefield since that will be a jumble of rim rocks, windblown dust and weathered fragments with little or no in-place bedrock exposed (or so I see now). The central dunefield would be suicidal: these are active, shifting dunes which have been found to be soft and dangerous to drive upon.

We are best served by keeping the operational Oppy mobile while we can, once we have a wheel (etc) failure then it can be made into a sessile base station.

--Bill

Here is Des Marais interpretation : "However, preliminary evidence from orbit indicates that southeast of the crater represents perhaps the most approachable trajectory to get inside the crater—if that go-ahead is given."
Not far from what you think, eh ?
BTW, Do you know what Des Marais means in French? "From marshes". Prophetic ?

Very nice, but I don't want to hear from Dr. Cassée Roue who works on the Spirit team.

If we have a healthy vehicle once all available outcrop has been examined.....who says we're not?

Yes - it's a long way off - and the balance will probably have shifted to the 'risk it' side of the scale compared to Endurance - but I hope some consideration is given to extraction when deciding an entrance strategy.

Doug

I am sorry to say, but there are no accessible bedrock at the bottom of Victoria crater, only sand. The rockface we can study are along the rim, but like most I do hope the rover will crawl in and have a look at the lowest strata that it can reach. Hopefully we'll get a lookback into one age older than those Endurance crater gave us some hints about.

I recall that was the attitude with Endurance. i.e., "If we get stuck, what a wonderful place to be stuck in." They were totally comfortable with the possibility of going in and not coming out -- a risk worth taking in exchange for the amount of science to be gained.

If Opportunity stays on bedrock, which seems wise, then bays A1 and P2 are clearly the most attractive as they extend ~80 and 60 m on bedrock toward the center of VC. Bays K1 and L1 hit dust (talus pile) almost immediately. The amount of exposed bedrock on a bay seems as important a factor as slope in picking an entry point.

Then why all the tests to see if the rover could climb back out again

Yes - it was 'if we get stuck what a nice place to be' - but that's not the same as 'we're going in and don't care if we can get out' They tested to see if they could get out, they were fairly confident that they could, and went in knowing that they would almost certainly get out again.

Doug

But they would not risk certain things within Endurance, like getting too close to the central drifts, or, I don't know, RATing Burns Cliff maybe - because there were still things to do after leaving. Here... Once they've exhausted the 'safe' things to do (and that will be a long time from now I'm sure), they might take a few more risks to get to the really tasty outcrops, before implementing any 'exit' strategy.

The decision to go down from the mountain or hill is one of the most complicated that I have. I had to study a lot it, searching the best way to get out (climbing) after studying the surface kind, slope and distance and also evaluate the capability of the truck to run out. This is the same thing that the rovers will apply before deciding to go down.

But, I agree as many others says that if the drivers knows that Oppy wouldn't be able to get out from the crater, the decision to go in only when the wealth of science from VC's insde is wealth worth enough.

However, I feel that in VC there are many ramps and exit ways. However, sure that going down there are more possibilities and it is much easier than to climb back which there are fewer possibilities of exit.

In many cases, the speed is very helpful to overcome the steep slope. However, Oppy is very very slow and but it is very versatil and light and the best way for Oppy to get out is on firm land slope as ones of Endurance Crater.

Rodolfo

Implicit in this: To get good resolution of all exposed layers -- it's better to see a spot from a 200 meter chord away than from all the way across the crater. In fact, more than 3 positions would be ideal, but not all of them would have to be a full pan. Also, TES is as important as Pancam, assuming it is still working through all of this. A lot of what is seen won't be touched -- TES is the best form of analysis for that stuff.

On that score, the dark slopes below the bluffs in those orbital pics that Tesheiner & others have been using for their route maps (eg this one) are suggestive (to me) more of scree slopes than rock ones. Especially given the streaks radiating in in many places, going from the bluffs all the way down to the dunes.

Still, we can but hope.

======
Stephen

A drive tosol (946) - One of the little test ones I suppose - I guess that means the checkouts yestersol were fine.

While the view ahead is incredible, a good photographer or explorer knows to turn around and look at what's behind you.

I noticed in these thumbnail Hazcams from the short drive away from Emma Dean Crater that there appears to be some nice clouds above Meridiani. I've compiled the shots into a 517k .gif animation. The ground was brightened a bit to show more detail. I'm assuming these are clouds and not lens flare.

Click to view attachmentFile:517k

Enjoy
Astro0

cool

Nico

A quick question for the geomorphologists - sorry if this has appeared in a different thread before. Some of Victoria's cliffs appear more or less vertical. The usual way to form vertical cliffs on Earth is by erosion from the bottom. Is erosion from the bottom a plausible mechanism inside Victoria, and if not how else do you form vertical cliffs?

Well spotted, I normally ignore those thumbnails.

Nice animated gif Astro0. I like the clouds very cirrus, I suspect they are very high up, also the the light on the soil is just about right.
Thanks
Roy F

Bluffs and ridges are formed when a less-resistant (to erosion) rock is overlain by a resistant unit. By Earthly example, in the eastern US with a wet climate resistant sandstone overlies easily dissolved (or weathered) limestone and forms sandstone ridges and limestone valleys. In the dry western US, limestone is resistant to erosion and forms hills and ridges.

What we are seeing here is that the unit underlying the cliff-forming evaporite is less resistant to aeolian erosion and tends to be removed. No idea what the physical properties of the weak unit are, but that remains to be discovered. The cliffs are vertical because as the support from the underlying unit is removed the upper resistant unit fails along vertical joints or fractures. One early example of an incipient slope failure is Fred's "Sluffing Slab".

--Bill

Thanks Bill. It has to be erosion from below then - I'm trying to picture this process at work. It seems to me the base of the crater walls would be a comparatively sheltered place, not exactly a hotspot for aeolian erosion. I wonder if there is any other possible mechanism for mass wastage from the lower unit. Could the Victoria impact have punched through to a layer with high ice content which would sublime away once exposed?

Well, there must be some amount of wind blowing about on and around the crater floor to produce and sustain those dust dune and ripple patterns... Maybe vortexes form down there sometimes, just gentle ones but long-lived, which sandblast the lower units? Wouldn't cause much erosion on their own, but cumulatively..?

I think activity above the crater floor plays a part too, tho. There are, to my eyes, quite a few scree spills and dust slides down the crater slopes (and something made that pronounced dark, tapering streak that slithers down the slope from Duck Bay), making me wonder if, during dust devil season here, the passage of dds nearby or even over VC disturbs the rim material and its structure sufficiently to produce mini avalanches of dusty material; we can see the southern area of the ripple field partially buried beneath material that has spilled onto and over it from the walls and regions above...

Just thinking aloud. I'll get me coat...

Good catch! They sure look like clouds, and the same formations are visible in both the left and right cameras, which would tend to confirm it, I think. That is a really cool sequence, because you can actually see the clouds move! Only thing is - they seem to be moving from east to west, more or less, and at a pretty good rate too. Is that normal, I wonder?

The observation times were from around 11:30 am to 12:30 pm, local Mars time, by the way, on Sol 943.

I think winds are intensified within craters on Mars, not reduced. For example, you might notice that a majority of dust devil tracks we see around the planet begin within craters. My thinking is that winds catch a crater wall and spin up into vortical forms. If conditions are right, these vorteces depart the craters and wander along the adjacent plains as dust devils.

In this case, you likely get the highest wind speeds along the circumference of Victoria, with the lag area of the winds encouraging the deposition of the dust that forms the central dune field. So, the most easily wind-eroded strata along the walls of Victoria would get fluffed off the walls (transported both out of the crater into the dark dust tails and into the central dune field), and the more-resistant rock strata become overhangs (or fallen overhangs). As Bill said, some overhangs form at the failure of the old rim along vertical joints and faults, while other overhangs simply slump onto the voids left below them and become "boat ramps".

What intrigues me is the evaporite layers, which we have seen are easily wind-eroded at ground level, seem to form the more resistant overhang layers on this rim. I'd be very interested to see what material is so much more easily eroded than the very friable, soft evaporite...

-the other Doug

Here's a Quicktime movie of the Sol 934 clouds that you can pause and step back and forth. It would be nice if there were more frames of this yet to come.

Last winter on Mars, Oppy was inside Endurance. And, IIRC, she saw a fair number of clouds during that period, too.

It would seem that clouds preferentially form over Meridiani during the winter.

-the other Doug

There is sure to be a feast of surface morphology to explain in Victoria. Thinking is definitely allowed! Most erosive processes though, including some you describe, tend to destroy vertical cliffs rather than creating (or at least preserving and accentuating) them. To do that you need differential erosion targeted specifically on the bottom of the cliffs. There has been no sign of this at the other craters visited so something is different at, or under, Victoria. In my mind I can't make sandblasting work because the sand would just pile up against the sides and protect the lower layers, moving the zone of erosion progressively higher. IMHO to sustain an undercutting process there must be a mechanism for completely removing the eroded or wasted material from the scene. On Earth the sea does this quite effectively as it forms sea cliffs, but inside Victoria there is nowhere for the stuff to go - unless it sublimed away.

Might frost formation/melting have some impact on erosion within VC too? The gorgeous pics/footage of clouds above the area show there's enough moisture here for condensation, so maybe the material around/inside VC is weakened by the formation and then subsequent melting of frost and made more vulnerable to wind erosion in that way..? After all, with all the berries and outcrop faces here there's a lot of surface area for frost to form on...

Does that mean that aside cleaning DDs, Opportunity will benefit of tranportation OUT of Victoria?...
http://i16.photobucket.com/albums/b14/ustrax3/ddfly.jpg
What will they invent next?...

Original image by Nico

That's a bit extreme but the fact that Oppy had a number of cleaning events while inside Endurance, had a major cleaning event on the approach to Erebus and has now recently had some more when approaching Victoria makes me think that o'Doug might have a poiint.

Ustrax,

I just love your cartoons ... they always make me like "schmeiss mich weg vor lachen"
(= "throwing myself away laughing" ;-)

TMAL !!

this place wouldn't be the same without your cartoons.

Nico

In re the effect of craters on wind patterns -- recall that craters undergo regular cycles of differential heatng and cooling, too. As the sun rises, it heats the eastward-facing slopes of the crater more than the surrounding terrain, and much more than the shadowed west-facing crater slopes.

Air rises over the heated slopes and sinks over the shadowed slopes. The bowl shape of the crater encourages a vortex-like pattern of airflow, making it racetrack within the crater itself.

Now, as the day progresses, the prevailing winds of the area pass over this crater. The racetrack pattern pulls up and involves this wind in its little circulation pattern, causing a local intensification of wind around and inside the crater. In some cases, this causes a much higher column of rotating air than you get from the crater heating effects along, a pattern that can sustain itself for several minutes. As the air mass that contains this vortex moves along, the newly-born dust devil departs the crater and wanders out onto the adjacent terrain.

I would think it possible that morning heating would produce one rotation vector, and afternoon heating would produce another, perhaps opposite, vector. I seem to recall that most of the dust devils observed by Spirit last Martian spring were in the afternoon. Perhaps the racetrack patterns induced by heating effects in craters are counter to Mars' rotation in the mornings, thereby less likely to cause dust devils, but become synced with Mar's coriolis effect to end up with reinforced rotation patterns and free-standing dust devils in the afternoons?

In any event, we *did* see evidence of overhang development, vertical cliff maintenance, and internal wind erosion in Endurance. And, of course, it featured a central floor dune field. So, I think that there is good evidence that the same aeolian erosional patterns were in effect in Endurance as we will see have sculpted the interior of Victoria.

-the other Doug

Wonderful, ustrax!!!! Of course, we're leaving aside the fact that the air is far too thin to support Oppy's mass...

However, I have these seriously cringing moments when I imagine her first attempt at *landing* after such a flight!



-the other Doug

Good point, I've been thinking something along those lines as well. Awhile back (Post #136), climber jokingly mentioned what looked like caves on the far side of Victoria. From a distance, they do indeed look a lot like remnant sea caves, very similar to some I've seen in the Callahan Divide of the Edwards Plateau in West Texas (the Callahan Divide was apparently once an island when the sea level was higher). Then there's that nice horizontal line visible near the base of the evaporite layer; I know it sounds hokey, but could that perhaps be a remant shoreline? Considering that we know that the ground in Meridiani was once wet, mightn't that suggest that ground water would translate into surface water in a depression such as Victoria? Realistically, any open water would have almost certainly been topped by a layer of ice, so the apparent "sea caves" would have to form by some process other than wave action (perhaps sapping?). Sheer speculation, but the first good view over the rim could be interesting.

I know we mustn't rush this, and I know the new software has to be checked out fully, and I know that this is probably the must crucial phase of Oppy's explorations so far, and I know that caution is paramount, and I know that there's good science to be done here, and I know that we should never really have got this far...

But Oppy, sweetheart, dearest, for the love of god, will you move! Just a little bit! The same view for two days!! Two days of constantly checking Exploratorium for new images (earlier today: after yet another F5 press two ****** thumbnail images of the Sun appear! The sun!!! ) and not seeing an inch further over the edge! This is just cruel...!!!

Relax Stu, I've just cleaned up the hard-disks here to cope with all the new data about to arrive...some of us will have lots of work once Oppy starts sending all those pancam frames over!

Nico

Hey, I will too... just starting (I think!) to get the hang of colourising the raws... not in your league, I know, but I'm itching to get stuck into some new material!

Yes Stu, I'm absolutely agree with you!
It's so loooooonnnng to waiiiit!
Also, I will go to the DSN antenna at Madrid and take the control of Oppy This would be a hold-up.
"Let's move Oppy toward Victoria or I send a killing message to the rover that will shut down the system! I'm crazy me!! Move to Victoria or Oppy will die!!"


Okay, I know the out -_-
Oppy, follw me! "Dzzzzzziiii

Wow - Conjunction is going to SUCK for you guys

Doug

well join the club then, there's actually not much to it as long as you're working with raws and something like photoshop.. more a subjective way of 'getting it right'.

I'm working on some real 'true color' the way Cornell does it, using interpolation of wavelengths and all that, just starting to get the hang of that and it ain't simple..

Nico

To quote Douglas Adams, "The knack of flying is learning how to throw yourself at the ground and miss."

Never mind solar conjunction. What happens after mission termination? Some of these guys may need therapy sessions or withdrawal counseling

Oh, what surprise! How well does Oppy fly?

Rodolfo

Well, I'll let you into a secret - there'll be no "mission termination"... right now a swarm of ET nanobots is heading for Mars and will descend on Meridiani in the dead of night soon, infiltrate Oppy's systems and effectively make her immortal. She'll be there to greet the first humans to land on Mars, and will still be trekking around the red planet when the first martians leave for Alpha Centauri...

Seriously tho, I'm just having a laugh ok? I know the importance of this "down time", and am fully prepared for the dark conjunction... but we're so close to those killer images now, so close...

( And Alex and Doug, don't you try and pretend you won't be lost without Oppy and Spirit too when their electronic eyes fade and darken for the final time; you'll suffer withdrawl symptoms as badly as the rest of us... )