As suggested in the "Victoria and her features" thread, we can discuss here the possible visit to Corner Crater (or whatever it will be called) [[ETA: now officially confirmed as "Beagle Crater"]].

Personally I think this will be a valuable stop, worth at least a run around 1/4 of the crater rim and a few days of MIs. Understanding the cratering process on Mars, especially the weathering afterwards, by examining craters of different ages can only enhance the understanding of the data we collect in other places.

Thanks Joffran, I agree with this new topic.
I think that CC is idealy placed, not only for what we'll see inside but even more for the effect it has had on the outcrops next to it since they have been moved more gently than at the place of the impact.

That's it exactly. Understanding cratering is related to understanding erosional and depositional processes on Mars which tells us how the present landforms evolved.

--Bill

Here's a simple anaglyph, vertical exaggeration x2 -just to have a look at 'Corner Crater' in this new thread.

Nico

Hopefully, CC will open a window into the local stratigraphy, thus giving us another point of reference; that's how you go about making geological maps!

Bob Shaw

Corner crater might make an interesting venue for the new flight software uplink (assuming that will be done using long HGA passes ) - and they could even manouver for slight sun-favourable slope somewhere around its rim.

Doug

Corner Crater is very interesting.

High contrast makes me think it's not very old.

Here is a de-anaglyphed stereo pair derived from Nix's fine anaglyph for us x-eyed buzzards who can see these things.

Whew, look at the boulders strewn along the way...

--Bill

I tried to post a more thoughtful reply here last night, but managed to lose it when my fingers inadvertently hit some mysterious combination of keys. Here is the executive summary. Corner Crater is obviously a target for the MER team, since they have been making a beeline toward it for some time now. Is that because it is an important scientific target, or simply because it is a distantly visible, navigation marker?

There is potential for science, no doubt. I think we'll only know that for certain once we get there. I expect at least a 180 degeree panorama. I also think the regional northerly tilt of the rock strata reversed a while back, but it is really difficult to be confident in that observation, considering all of the local variations we've seen along the way. It may be helpful to catch some good observations of the rock layers in this crater prior to climbing onto the main ejecta blanket, if only to attempt to learn where in the sectin we might be.

Ignoring all of the above speculation, making ground truth observations of craters on another world will always be an important objective, considering their value in estimating ages, erosion and deposition rates, elucidating stratigraphy, etc. As we learn more about Mars from the rovers, it seems to me that we learn more about how to make the kinds of estimates we need in order to interpret the geology on other worlds. To use a metaphor of the PI, they are our boots on the ground.

Well put, Tom. My first informal-name for Corner was "Bullseye Crater" since that was what was happening.

On Mars, craters are our roadcuts...

--Bill

I think that Corner Crater is an interesting spot. The interior of the crater look very dark and the rims are very bright and strangely elevated, as a sort of "wall". This could be an assembly of layered rocks du to the impact. I've a question : is it a single impact or the impact happened when Victoria was created?

I think it's a combination of both factors, and a third one: The rover's path is constrained by the dunes/ripples orientation usually between 160º-180º (SSE-S), and that path places Corner Crater on the way.
I would consider CC as a "bonus", and really believe they won't miss the chance to investigate it.

Corner gives us a cross-section through the outer edge of Victoria's ejecta blanket, down to the pre-Victoria land surface.

--Bill

Ant (mind if I call you Ant?), CC is surely interesting for the reasons already mentioned. The apparent depth, the rim "wall", and the ejecta 'rays' that give it an asterisk appearance, all are characteristic of a geologically recent impact. Whether that means a thousand years old or a million may be hard to say, but it certainly is less degraded and so newer than VC. If it is a primary impact, there may be recognizable fragments of the meteorite impactor in the area, but I'm not sure that the PIs will be willing to spend the time looking for them.

The CC is a very original crater. The whitest ones. taller rims than any visited by Oppy on its way from Eagle. I agree with most that CC is younger than VC since its rims is less eroded and also it is on the VC's influence of impact. Hopefully, Oppy will spend many good sols sniffing on CC which favours my bet of outlook VC arrival date.

Rodolfo

Maybe we can find tehre a connection to the brightness of the beacon...

What a pleasant, chatty leisurely thread this is, away from the frenetic passions of false democracy evident elsewhere….

I agree that “Corner/Bullseye/Whatever-JPL-Will-Call-It” is post-Victoria, relatively fresh, and it really does look fascinating already. I don’t think we’ve yet seen a crater rim so clean of the Meridiani drifting dune material. Speculating on what is perhaps a rim of pale broken evaporite ejecta blocks piled too high to be inundated with dark drifts, I have been thinking of the different types of crater morphologies we’ve seen on this voyage.

Eagle had no blocks on its sandy rim, while Endurance did have a bedrock exterior rim in places, but lacked scattered ejecta. I keep coming back to little Fram around sol 88, which is fresh enough to have exterior and interior broken blocks, inter-laced with the ubiquitous dark drift. This is in contrast to a significant little crater we passed on sol 818 (new pancams just posted, but I don’t have the skills to make a proper pan). This is perhaps a bit larger than Fram size and has a clear circular bedrock rim but not much blocky ejecta evident. The rim of this little crater reminds me of the Payson edge of ancient Erebus. Is it just millennia of slow erosion that turns a jumbled Fram into a flatter crater 818?

Maybe not that simple. What happens when a big impact like Victoria occurs near to an older Erebus or little crater 818? Doesn’t a powerful supersonic wind scour the landscape for miles around, blasting away the loose ejecta of older craters and flattening them down to look like rimless Erebus and 818. I don’t know whether this is a recognised phenomenon in this field of study, but it does seem to me that big impacts in an atmosphere, like Mars has, are very different from say the moon. And proof if needed that Corner with its raised rim post-dates Victoria.

Kenny

....gasp...whew....'scuse me while I catch my breath in here...
Yes indeed, Kenny, the shock waves, hypersonic blast of superheated air, and gravity flow of proximal ejecta are all parts of the latest hydrocode modelling for impact cratering. I've seen no studies of the effects of these on a neighboring crater, because the research focuses on the larger, more scattered craters on Earth. I have little doubt though that Victoria impact vastly accelerated the erosion of Erebus and any others nearby at the time. The thing about Mars that confuses the issue is that the vast stretches of time surrounding the current topography, combined with a currently slow rate of erosion, allow for multiple cycles of deposition, cratering, burial, exumation, and reburial. If you follow the MOC images at msss.com you've seen copious evidence for these cycles. When a crater, like Corner, has the classic features of freshness, we can assume that it has escaped these cycles. As for the rest, without raised rims, blocky ejecta, etc., who can say?

...right...back into the fray...

Thanks for the X-stereogram, but... boulders? I see no boulders along the way, only drifts and outcrop flats. Are you sure you have your eyes crossed properly?

Otherwise it seems clear that CC is sitting on a ridge - the ground behind it is not visible for a long way off.

Before the left half of the crater about 2/3 to 3/4 I see rocks larger than usual. Boulders may be an exaggeration, but they're bigger than the usual cobbles...

--Bill

I'll agree on a boulder aligned with the east (left) edge of CC, most of the way there. The other white flecks I'm not sure about yet, we'll see!

The dark feature on the horizon, has this been visible/discussed yet?

Would that be the edge of the crater ?
Nico

I wondered about that too, Tesheiner straightened me out that its the little craterlet on Victoria's blanket in this thread.

Interesting how close it looks from here, and if we can see its profile, it really shows that Victoria has no substantial slope up it, were looking pretty flat and there is no slope hiding Victoria's lower flanks. its somewhat of a sunken crater compared to Endurance. Makes me wonder if it compacted the underlying landmass by melting the permafrost or rock, sinking the whoel assembly minimizing its profile on the horizon. Which might account for the small rise separating Victoria and Erebus.

This is what I think we're looking at. These images are adapted from Nix's anaglyph (de-anaglyphed) and Tesheiner's Route Map (South is up). The edge of the Victoria rim on the left may actually be the nearer west rim, but you get the idea.

--Bill


NOTE: I agree with Joffan, and re-did the image to point at the proper rim-spot on Victoria.

I agree that the rough patch on the horizon is the small crater you identify in the diagram Bill, maybe that should be "Garter Crater". Your green arrow should perhaps point to the same place as Tesh's Infallible Route finishes.

I think I was wrong before about Corner being on a ridge; it's just the uniform dark ejecta behind it that gives the illusion of distance behind it.

It's just another beacon. My gut tells me it's on the far rim.

In re the discussion of crater morphologies, specifically as seen in the Meridiani area...

First, if Mars' cratering history is anything akin to the Moon's, then a vast majority of the visible craters were made at the end of the Late Heavy Bombardment. Yes, there has been a continuing cratering process, but the rate has been much slower.

Second, the LHB occurred back in a period when Mars may have had a much thicker atmosphere and a lot more volatiles in and on its crust.

I truly think that one factor in the cratering morphologies is the relative volatiles content of the impact target. I think the old, very subdued craters may have been made by impact into soggy ground (or perhaps even water-covered ground). Sharper-looking craters were made after most of the volatiles disappeared. The former feature subdued rims and ancient crater fill almost level to the rims, while the latter feature much more lunar-like morphologies, arguing against the presence of volatiles in the targets at creation.

So, I would argue that Eagle, Endurance, Fram, Victoria and Corner are all examples of impacts into a dried-out ground target, while Erebus, Terra Nova and other ancient craters in the etched terrain are examples of older impacts into a ground that held an active water table, close to the surface -- if not actually into a body of water.

-the other Doug

This all sounds logical, DV, but won't a more parsimonious explanation suffice: Eagle...Corner formed in the last 500 Ma, and Erebus... formed in the 500Ma before that. In other words, do we really need the LHB and the "wet" period on Mars to account for what we see on Meridiani today? How can we distinguish without absolute dates on the craters?

We've not really had the chance to examine smaller craters on the ground before the MER missions, but there's a clear set of crater morphologies visible from orbit which certainly *do* demand to be interpreted as impacts into volatile rich materials: the uniquely Martian 'rampart' craters. These are characterised by an ejecta blanket complete with flows, and ending abruptly in lobate scarps. Such craters often resist later water erosion, too, and can form islands in the midst of some of the catastrophic floods.

How tiny craters work in volatile rich periods and/or materials is interesting - but we must remember that secondaries will predominate, with much lower impact speeds and thus lower overall energies.

Bob Shaw

Good points, Bob. And Shaka, as for the importance of knowing how volatile-rich the targets were when given craters were formed -- I would think that this would cause more than just morphological differences. We ou ght to be able to see differrences in the rock types making up the ejecta.

I would think that ejecta from a volatile-rich target would be mineralogically quite different from that from a dried-out target. Without plugging that potential difference into our analysis of the minerology around each type/age of crater, I don't think we're going to be able to come up with analyses that make sense.

-the other Doug

I quite agree, DV, but I'm not sure whether MER is equipped to do these analyses. To start with, we have to find some of the original impact-altered ejecta or melt breccia. That may be a tall order for craters dating back to the wet period. Then we need to analyse for water and other volatile products. Tough row to hoe.

Agreed -- though, to be fair, the MERs were specifically designed to find traces of water in the minerals. They may not have been designed to fully characterize the soils and rocks, but the MER instrument suite was targeted at discovering water and water alteration to rocks.

So, assuming we do find some samples of the original impact melts, we sure do have the right set of tools available to determine their water histories...

-the other Doug

Well thanks, Other Doug, this does give a start on a plausible sounding explanation for the crater differences that had intrigued me. I could envisage a Fram-type blocky rim turning into a sofer Eagle-type rim with age, but I was struggling to see this evolve towards an Erebus-type, the flat rim with a sharp scarp edge.

Kenny

I hope you're right, DV.
I'm no geochemist, nor do I have any thorough knowledge of the full capabilities of the spectrographic tools on MER, but my ...(dam', nearly said "gut feeling")...my impression is that they were designed to look for mineral species produced in the presence of water at 'cold' temperatures - such as our famous gray hematite. The process of impact melt production is definitely a high-temperature process and may result in different mineral species, to which MER are insensitive. But I don't know.
I do note, however, that there are researchers who managed to get published 'high-temperature interpretations' (viz. impact and volcanic) for the supposedly low-temperature hematite and evaporite we've been riding across since we landed. So maybe the mineral distinctions are not definitive.
Anybody know for sure?

I was looking through the new pancams after Oppy's latest great escape, and there seemed to be more loose bright stones lying around (an example looking roughly west). I wonder if these are the outer edges of the ejecta from Corner?

That's certainly one hypothesis, and if they continue and get even more numerous as we roll south toward CC, I will favor that one. If they get rarer, however, I will propose that they splashed away from the big rubble piles to the west. Those piles may be the remains of big (pickup truck-size) pieces of ejecta from CC or some other recent impact.

Joffan:

Seems reasonable. And as for mini-craters (discussed elsewhere), what we want is to see a nice, fresh one, complete with the impactor - we have certainly got a smoking gun in the form of CC...

Bob Shaw

Could the study of the outlying ejecta from CC end up providing more clues to the timing of (dune making) events in Meridiani than Corner Crater itself? Perhaps a lens of ejecta covered up by a thin coating of the dune material as exposed by a wheel trench?

I would think it quite possible to learn about relative timing. Absolute timing is another matter. Until we can do radioisotopic dating here, that's likely to remain a black box. Mars just smiles like Mona Lisa, and says "Guess."

Fresh news from the front:

First I asked Steve Squyres if Corner Crater would be the next planned target:

'Our next major landmark will be a fairly fresh crater that lies about 500 meters this side of Victoria. I think it's roughly 35 m in diameter, so it's probably the one you're talking about* . We've named it Beagle crater. It's named, of course, for Darwin's ship, but the name is also a tip of the hat to our British colleagues who headed for Mars about the same time that we did.'

Then:
There were some thoughts about the nature of the terrain Opportunity is now traversing:

'It appears to me that Opportunity has recently decended into an ancient crater... whose circular outline is apparent on Tesheiner's maps. The decent can be seen in recent anaglyphs from Opportunity. It appears to me that the crater's basin is directly in our path, and I wonder if the aeolian sediment in this crater is more treacherous than elsewhere, and responsible for the recent wheel embedding hazard.' (CosmicRocker)

Looking into the separating the rover from Victoria I think I can see what he means:
http://i16.photobucket.com/albums/b14/ustrax3/scr.jpg

And it looks, in my opinion, that this represents, in fact, serious possibilities of seing Opportunity stuck again...
If this is correct your idea is to keep on following the rocky road and, in the absence of it try to stick to the contour of those old craters rim?

'Regarding our path southward, we'll always travel on rock when we can find it. The terrain we're in right now just doesn't have a lot of rock, so we'll pick our way through it as best we can.

Cheers, SS'


*corner crater

What will our little and dusty Darwin discover there?...

ustrax, thanks for sharing this.
Direct communication with SS, not bad.
But I have to remember that Mr. ustrax isn't an average man. He's involved to name features on Mars !

Beagle Crater... hmm, I like it.

Image of beagle trotting along at the hem of Queen Victoria's skirt...

Beagle crater, that's ok; but it'll always be Corner Crater too.

Then again, if we renamed Victoria as "Doghouse"...Click to view attachment

Time to return on target:
Sol843 - stitched and merged (left+right) images, without and with 5x vertical stretch... go Oppy, go to Beagle!
Click to view attachment
Click to view attachment

I'm afraid the other Beagle ended up making a crater too

Thanx, Amico, I needed an image 'fix' badly.
Say, no one's mentioned it, but there's a nice black beacon right in Beagle's middle. Probably a shadow.
What do your observations indicate about its location? Near rim or far?
Shirley, wanna take a poll?

Thanks for the merged & stretched look-ahead images. I hope we can still make good travel times, I note a _significant_ change in the sand: there are a lot of small ripples across the N-S trending major ripples, and this is worrisome. It suggests that this sand is "fresher" and actively moving and looser, so Oppy may have to pick her route carefully.

--Bill

For cross-eyed stereo fans, here's a view of the road ahead to Beagle Corner:

Click to view attachment

The black Beagle beacon beckons...

When I see the surface from Oppy to Corner Crater that is more uneven surface. It might mean, just my toughts and nothing sure, that there has more wind or turbulence wind zone caused by VC and hence sand is looser.

Rodolfo