I'm sure the dark streak is a cosmic ray hit. Normally when they strike the ccd they form a white (positive) image, but I believe if the timing is just right the effect of the strike can be subtracted from the image, forming a dark (negative) streak. I'm sure there are ccd experts here who can verify this.

Is it me or is the Victoria apron beginning to look distressingly ripply? I wouldn't call its appearance in the sol 878 drive direction pan "featureless" at all...

--Emily

It's not just you. It looks more ripply to the south, though, less so to the southeast where Victoria is. (And I hope that's not just an illusion of some sort.)

Much of that pan seems to be centred towards the south/east I think, where the dunes remain.... over towards Beagle Crater, i'm sure it looks MUCH smoother.

I'm intruiged by this dark sandy crater (?) to our south-southeast (sol 878 pancam view):
Click to view attachment
Why does the sand appear so dark? Is it just the lighting angles on the slopes of the crater?

I've identified it on Tesheiner's route map - the green arrow points to it:
Click to view attachment
This crater is neither of Alpha, Beta, etc identified previously.

Could it be it's caught the eye of the rover planners? Perhaps we'll swing by sandy crater, then follow the outcrop highway back to Beagle.

From Fredk's identification, that "crater" is not a crater but an isolated mound of the ejecta blanket material sitting on the evaporite. The sun in this MOC image is from the NNW at about 65 deg altitude.

--Bill

The longer I look at the shape from above it appears less and less like a crater. It looks instead like a round shaped dune sitting atop the evaporite layer. I've highlighted two other similar objects in this image that are likewise situated at the boundary of the upslope transition zone. All three appear to be associated with Victoria's apron material.

These were noticed earlier in this thread and identified in the subsequent discussion as clumps of Victoria's ejecta blanket. There are two prominant clumps which have been visible for the past several days or more, which I've lately begun mentally referring to as the "East Hillock" and "West Hillock". The one you've pointed out would be West Hillock. East Hillock is currently a bit subdued from Oppy's current perspective. I would speculate that it is dark due to being A) basalt sand like the rest of the ejecta and probably solar angle. As ElkGroveDan mentioned, there may be another smaller hillock behind Beagle. I'd guess that similar features are scattered all about the boundary of the ejecta blanket. It occurs to me that the dynamics of ejecta blanket deposition must be similar to that of a volcanic pyroclastic flow ... implying that we might find similar features around the base of Mount Vesuvius.

That's it exactly, Algorimancer. The energy of the impact essentially fluidizes rthe rock and it becomes like a pyroclastic flow. I was thinking along those lines but couldn't quite verbalize it. I wonder what happens to the overlying evaporite? In the "gentle cycle" scenario the evaporite and the underlying basaltic unit are gently flipped like an omelette. But in reality there is a lot of heat, shock and violence and I wouldn't be surprised if there was some metamorphosis occuring-- what happens when you mix pyroxenes abd olivines with sulfates under heat an pressure? The "Hillock" features will give us an excellent insight into the impact processes.

--Bill

I guess it's possible that some primary depositional features of the Victoria ejecta blanket might be preserved here, but I think it's unlikely. The fact that Victoria's rim is almost level with the surrounding terrain suggests that there's been a *lot* of erosion, and the landscape probably bears little resemblance to how it looked the day after the Victoria impactor hit. We'll know soon enough.

Exactly the point I was about to make, John -- that and the morphologhy of the ejecta emplacement is a lot more visible and obvious at a distance (a la in the MOC image) than it will ever be on the ground.

I do have some hopes that Beagle is young enough to provide a drill-hole through the transition between Victoria's visible ejecta apron and the outlying terrain, which *could* have exhumed some primary depositional materials from the much older Victoria impact. That's why I think it's reasonably important to at least get a good mini-TES pan and a good multi-spectral pancam pan from the rim of Beagle.

At the very least.

-the other Doug

Well, if Edgett's idea about Victoria is correct, the crater has undergone significant erosion, deposition, and more erosion. It appears to me, from the MOC images, that Beagle is actually just outside of the ejecta blanket, but it is hard to know for sure. The bedding in this area seems to be maintaining a slight SE dip, close to what we've seen elsewhere, except right near Beagle where we see some disruption.

Regarding the dark hillocks, these must surely be just more examples of the dark drifts we've been seeing on and off for some time now. They are dark because they have a concentration of the small dark cobbles on their surfaces. They have become more numerous the farther south we have come. Previous examples can be seen in the pans from sols 817, 864-869 (this one is even in false color), and 871-873. I've long speculated that these are the result of basaltic ejecta fragments that have weathered in-place to become concentrations of dark clasts. They sometimes appear as lag deposits, and sometimes as a part of the armoring on the drifts.

As for the possibility of flying past Beagle without a scratch-and-sniff stop, no way. I think Beagle is clearly the next science target. They will likely follow the southerly drift grain until there is an obvious, zero-risk point where they can turn and head directly for Beagle.

Lastly, while there do seem to be some ripples on the lower stretches of Victoria's apron, it does become quite smooth further up. I'm sure SS's "featureless" comment was not intended to be taken literally.

Good comments, CR, o'Doug and john_s. This locale will be a prime science stop of the mission. Although looking into Victoria will be great geology, to a certain extent, it's also an eye-candy stop. The importance here is that understanding erosional-depositional processes is understanding Mars.

Attached is a clip from MOC image R11010300 showing an interesting ejecta pattern here on the Plains. Although this may be an extreme example, the ejecta apttern is not always a neat "splat".

--Bill

Off topic, but I wonder if that isn't an example of the 'butterfly' characteristic of low-angle impacts? (eg. http://en.wikipedia.org/wiki/Rio_Cuarto_craters#Formation - not a great reference I'm afraid.) There seems to be a bilateral symmetry with two dark lobes heading off at more than ninety degree different directions.

At least in large impacts a large amount of gas is liberated by the heating of evaporites and other sedimentary rock (CO2 from carbonates, SO2/SO3 from sulfates). This has been well studied for the Chicxulub impact. However I'm uncertain about a small impact like Victoria. Offhand I can't think of any small terran impact crater that is in sulfate rocks (which are not that common on Earth). Still, as you say, I would expect at least some metamorphosis/melting.

tty

I hope this doesn't sound too pessimistic...

The more I look at the best pictures of the Victoria ejecta apron, the more convinced I am becoming that the surface of this apron consists of soft, maybe impassible dunes. I am thinking that the reason it looks more flat is that the underlying substrate is dark, and so the visual contrast is a lot less (although the dunes are not). If you look closely, particularly at the outer parts of the apron, you can faintly see dunes. And the distance panorama pictures from Opportunity of the apron to me show it is dune covered. So I am thinking that the apron surface consists of dark dunes on top of dark soft soils.

So here is my prediction: the apron will be impassable. We won't reach Victoria.

I sure hope I am wrong!

Rocker touches on some key issues here. Regarding the 3 excerpts above, I would comment as follows...

1. It seems to me that Beagle Crater is just outside of the area of surface deformation caused by the Victoria impact, delineated by the white Scarp we now see in both orbital and surface pics, but it is certainly not outside the ejecta area - Bill and I and others commented on the likely cobble ejecta of Victoria we were encountering over 25 sols ago.

2. The dark hillocks are weird. They surely have aeons of drift deposits accumulated around them, the same material as forms the dunes, but there must be something else more substantial at their core which causes the elevation we see. It's hard to imagine any aerodynamic effect which would raise dunes so much higher at those points, if they were only dune sand. Maybe they are Victoria ejecta piles covered in dune sand.

3. I said (maybe in another thread) that beyond the Scarp we have ripples leading to smoother areas, and earlier postulated separately the view that the smooth inner apron is "sticky" flat sand like we saw outside Eagle Crater, with great traction and fast mobility. I'll still go with that, but as always am prepared to be surprised!

Kenny

Thanks for the thoughtful comments, kenny. It appears to me that only some of the dark hillocks are large. We've seen them in medium and small sizes, and indeed have even seen some related dark areas that are not even hillocks. I can think of a reason why some of them are large. If there was once a large block of ejecta that has since disintegrated into tiny fragments, it would have initially been a barrier to the wind and might have caused large drifts of fines to accumulate around it. As the block disintegrated, the larger dark fragments would have accumulated on top of the drifts, since they were too large to be moved much by the wind. An accumulation of coarse, unmovable clasts on the surface of the drift creates what is called an armor, which retards erosion and movement of the landform. The remains of the original ejecta block may still exist in the cores of these things.

[edit] Oh, and I forgot to mention that I am prepared to be surprised too, but I think you are dead on with #3.

That is why I've done so much arm-waving to get Oppy to stop at a cobble-field or a rubble-pile. These isolated "ejecta outliers" are perfect to study and are a good puzzle-piece instead of a whole puzzle quadrant, as the ejecta apron will be. We have stopped at one of two cobbles and did MI and MB work, but that may not be the full spectrum of properties. The cobbles were determined to be "basaltic" and they may know more about other dark cobble exposures from mini-TES work, but we don't know for sure and I'm still curious.

My 2c.

I'm not sure what the nature of ejecta apron surface will be. I'm certain that it will be pulverized, shocked and discombobulated basalt from below the evaporite but I'm not sure of the details such as particle size distribution. I don't think that it will be similar to the plains between Eagle and Endurance: that was a mixture of (basaltic) sand and angular fragments, and a large percentage of Blueberries. The big difference will be the lack of Blueberries, and these two soils have a different genesis and history. My concern is not sand (in which case we'd be seeing ripples and dunes) but boulders (much like the rubble-piles we've seen). My intuitive hope is that we'll be driving over gravel, but Mars is full of suprises and this is THE major change in terrain we've encountered.

Attached is a montage of surface MIs taken early in the mission (pre-Endurance).

--Bill

Hello.

Here is my first anaglyphic panorama. This one show the view in the drive direction.



What do you think of this try?

Well, yeah. It sounds a little pessimistic.

In years of driving across kilometers of Martian terrain, neither rover has come across a large impassable area, only impassable spots, usually individual dunes or highly sloped spots. Problems with soft spots have had a slope element that I don't think applies to the entire Victoria apron.

Dune fields come with breaks and inter-dune paths. So the only trouble could be a surface so soft and yielding that the rover sinks in. (Reminds me of the fears of moon dust swallowing landers.) I think the surface will be compact enough to traverse. This has been the experience so far over years and kilometers of travel. They only have to avoid hitting a ripple at the wrong angle.

I think the biggest real danger is that one of Opportunity's wheels locks up. That could stop passage over any dust/sand surface as it did with Spirit.

Here is a Quicktime movie of Opportunity's voyage south from Erebus, so far. It's 7.2MB, and it may be best to right click and download it rather than viewing it in a web browser window so that you can size it down a bit.

Opportunity's Voyage South from Erebus (Quicktime 7.2MB)

The movie is a series of 61 MMB Navcam panorama views facing due South, angled 75 degrees down and zoomed out to show the surrounding terrain.

Wow!:blink: Your video is very good and we really have the impression to "fly" over and with Oppy. The end of the animation is great.

Looks like another meteorite caught Oppy's interest, at least enough to take a little color picture of it.

From Sol 875 (but just showed up today):

Click to view attachment

Based upon a stereo pair from Sol 873, that's on the order of a meter across. Pretty hefty.

Intriguing. Here is a view showing the context:

That is nicely done. Is this sort of thing a feature of the MMB now? It's been a long time since I last upgraded.

It's been a feature for ages, it's puts the images where they're supposed to live

Doug

Awesome video Michael!

Nico

Yes, that's been a feature for quite a while now. The pans are assembled from info from the Pancam Tracking Database, so everything is in the correct place automatically - plus or minus a manual tweak of a degree or so for the difference between Pancam and Navcam, and assuming the data in the Database is correct - which it hasn't been on a few rare occasions . I repackage the info from the Tracking Database and put it on my own site, by the way, so MMB does not hit the Database directly. I want that thing to stay accessible.

I love that in that image, you can see the feature we think is Distant Crater Rim - not Victoria, mind you, but the really big one way to the east.

Good to know. I just installed the latest version...

Back to the Hillocks question... the flaw I see in the reasoning that much of the original crater has been eroded away (yes, I've seen the paper), is that I don't see much sign of any overlaying sediment layer. I see the type of terrain with dune covered evaporite that Oppy's spent so much time driving over, and overlaid on that is pretty clearly an ejecta blanket. The notion that the hillocks are not associated with the ejecta blanket defies Occam's razor; sure there's the occasional larger than usual dune out there, but observationally the hillocks are clearly associated with the ejecta boundary, and appear to have the same color and texture as the ejecta material. The obvious conclusion is that they're ejecta material (until more evidence says otherwise).

One thing that does puzzle me is the evaporite "ring" around the ejecta blanket. I'm having a hard time envisioning a mechanism for preferentially clearing the dunes from the evaporite at that interface, unless there's a much steeper transition onto the ejecta than appears to be the case at the moment. Intuitively I would expect the dunes to just keep marching unimpeded across the ejecta blanket, so that the only difference between being on the blanket and off would be sand versus evaporite in the troughs.

Then there's the question of what happened to the evaporite blocks presumably blown all over the place by the impact. Where are they? We see blocks around most of the smaller craters (not so much around Eagle). Either they were blown to dust, or their absence is a sign of that surface erosion process... they were there once, but there has since been sufficient erosion to remove them. And if there was that much erosion, yet the hillocks and ejecta blanket remain, the conclusion I arrive at is that the erosion process predominantly targets the evaporite, but leaves mounds of basalt sand undisturbed.

That evaporite ring at the leading edge of the ejecta is puzzling. I've had varied theories about it but I keep discarding them. We'll be spending some time here...

Here is an L257 Pancam of the mottled area (and supposed mirrored evaporite dessication cracks) from what I think of as the "Oy Vey Dune" at the recent detour.

--Bill

Cool! I hadn't noticed that one, either.



I call it "What Were We Thinking Dune". However, they found some interesting stuff on that little side trip, so maybe they are crazy like a fox instead of just crazy.

Are we still seeing hematite granules eroding out of the evaporite, or is that something else? Or do we know?

As an aside... if the evaporite is eroding preferentially, might some sort of chemical weathering be involved?

And the same in approximate true colors

Well while we're playing "compare the colours"

I may be over-interpreting things, but to my eye these Sol 879 Pancams of tracks look distinclty drier and dustier than the "sticky" dunes tops we saw earlier.

http://marsrovers.jpl.nasa.gov/gallery/all...AZP2548L7M1.JPG

Kenny

We're talking a different mechanism here though. Before, it was ploughing deep into a dune. Here, it's a bit of a pile kicked up by the FR wheel that has a stuck steering actuator being dragged through the surface and then the pile being driven over. You're always going to get a different 'look' to tracks with such different mechanisms of creation.

Doug

From what we've been seeing in the evaporite and on the surface it looks like the concretions are the source of the blueberries. Unless another idea has been accepted. In a ideal world we'd get some MI, a RAT and an MB on a "typical" undisturbed Burns outcrop before moving onto the Victoria ejecta blanket.

The "What Were We Thinking Dune" was unusual and it'll be interesting to hear the story behind the story some day. Attached is a Front Hazcam view, cropped and enhanced, of what I think is the backside of that dune.


--Bill


PS: 7/19/06: Oopses, that Hazcam view was of the eroded crater we passed by, not That Dune....

There is a rock that looks like a wasp's nest visible in Opportunity Sol878 Navcam images.

see: http://origin.mars5.jpl.nasa.gov/gallery/a...unity_n878.html

The best shot of it is:

http://origin.mars5.jpl.nasa.gov/gallery/a...ZP0695R0M1.HTML

There appear to be folds in the interior of the rock. Has anyone seen something similar before? If the event which formed Vic postdates the dunefield, perhaps it is ejecta? Sure looks weird though.

Hopefully they'll take some pancam shots.

Thanks for an excellent forum!

Mark

That is intriguing. The surface texture and color seem to be the same as most of the sedimentary evaporite rocks that we have seen. But the shape, and especially the almost hollowed-out appearance seem similar to a lava bomb. Would any of the geologists care to give us their best educated guesses as to what this is?

David

This rock caught my eye the day these images came down and I've been mulling it over. It is a piece of ejecta, likely from Beagle, and it is sitting on the plain quietly weathering and eroding. The unique thing is the area of "folds" that you have noticed. I'm thinking it's a fracture fill, an area where a fracture has been filled with a minerals deposited from mineralized groundwater.

More later: I hear an approaching t'storm.

--Bill

Yeah, It caught my attention, too. I remember you mentioning it Billl, and meant to respond, but I ended up getting distracted by something else. I hate when that happens.

Other than its general shape, it seems not to be a lava bomb. It is most likely a piece of bedrock based on it's color and the thin bedding visible on the left upper surface. But that dark core area crossing the bedding is really anomalous compared to any rock I have seen so far. It really looks to be some kind of secondary alteration or mineralization. There really appears to be no folding involved, but rather, as Bill mentioned, some relationship to the evident fractures.

It's a shame we only have the navcams, since this piece of float is worthy of more than a glance. One pancam image would show so much more with essentially a 3X magnification. While we have been sitting in the same spot for several sols, I'm really disappointed it hasn't been targeted for at least a set of subframes.

If my data tracking skills are up to scratch then then I think you'll be pleasantly surprised when you see the 881 pancams.

I beleve that "881 p2551.16 13 13 0 0 2 28 pancam_redrock_L234567Rall" is pointed in the direction of that rock. (no thumbnail images at the tracking site to confirm this yet though)

James

EDIT: And in case your wondering the other 881 pancam target "Preston" appears to be the other nearby rock.

EDIT2: Thumbnails are up - this is confirmed.

Does anybody have any information on that new software update?
That must be the reason why there are no movement for the last couple of days...right?
Today [ sol 882 ] plan:

Probably just the PC tracking site lagging a bit - I wouldn't worry.

They've said they'll deploy the flight software update in August ( Opportunity has the whole upload, Spirit was one file short as of the last FDU )

Doug

Well it has been the weekend so no surprise that we've been stationary. (although somewhat surprising that there was no 'preprogrammed' drive at the end of the weekend (yestersol))

The lack of anything on the tracking site for 882 is strange - could be rebooting into the new software I guess

James

Edit: Crosspost. I was going to suggest a problem/lag with the database as well - but it's generally been updating well today. We'll see...

How is it going to be like?
Installing new Flight software...
this may take few minutes...
please wait...
New hardware found...Mars Exploration Rover
...searching for driver...

Hopefully we'll get closer views of this chunk of ejecta, but as hopefully we'll see more examples in the Beagle roadcut. Also the bedrock exposure at the leading edge of the ejecta blanket has a unusual "mottled" appearance in MOC images, so that is of interest. I'm thinking we'll be looking for features related to the Victoria impact.

I've got an x-eyed stereo pair of this rock in the works, but I'll leave the anagram to someone else...

--Bill

Cork this? Ski torch? Sick Thor?

Apologies for the signal to noise degradation but I couldn't resist.