The circular pattern you marked is just from the "wheel within a wheel" in the rat grinder tool - nothing unusual here.

Maybe this is a new grinding mode? Don't the 'wheels-within-wheels'
normally orbit around the center of the RAT as they grind? Are these
circular impressions seen because the smaller grinding wheels' orbiting
motion has been stopped in this instance? I don't recall seeing these
patterns in the past. Or is it because MI's have been taken after grinding
but before post grind brushing and this is not normally done?

With the grind encoder defunct and the brush bent I would attribute the grind pattern to their work around.

It didn't take long for me to find past MIs with the same
sort of pattern. It's just that this time there is a great contrast
between the clean small grind wheel circles and the very
dusty look of the rest of the larger, overall RAT circle.
I don't know if the dusty areas are that way because they
took the MIs before brushing, or if the brush does not work
well enough to do a better job of cleaning.

Im working on it. Should be ready by tomorrow. The problem is trying to find a good image to work by with. Thats why I make my own mosaics(they are very *crude* mosaics but they serve the purpose).

I am particularly intrigued by the prospect of Oppy ever finding clay deposits beneath all that sulphate-rich sandstone. Any news on that anyone?

The following paper seems to provide an answer to your question:

http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1171.pdf

This paper is of the opinion that "The sedimentary rocks examined by ... Opportunity ... are part of a statigraphic sequence greater than 1 km in thickness". It also states that "The amount of rock that once covered the MER-B site could have been as much as 200-300 m".

If these estimates are correct then Opportunity would need to find a crater of at least 700m in depth if it was to have a hope of finding the clay deposits beneath the sulphate rich sandstone. Victoria at only 70m in depth is clearly not deep enough to provide exposures of clay deposits.

As has been suggested before on this web site Ithaca crater might be deep enough to allow clay deposits to be investigated. Unfortunately as has also been stated Ithaca crater is many km away at the far side of a large impassible dune field.

I've seen scattered reports of clays detected by orbiting instruments within Meridiani, but specifically with regard to your question about clays beneath the sulphate-rich sandstones of the Meridiani plains, I noticed the next to last paragraph in this news release recently. I'd like to hear more about that.

Alright here is my diagnosis for a 'possible' approach to Cabo Frio.

So far it seems to be an easier target and Oppy can get as close to it as she can get.

However there is a sand drift(marked red in both images) that may give the rover some trouble.

Cabo Frio is approx. 85m away.

Reviews are welcomed.


Click to view attachment

This shows the view from the top of Cape Verde.
Click to view attachment

Fascinating, Doc. Assuming we continue our Duck Bay transect down to the limit of visible bedrock slabs (off the left side of your image), we will then have a choice of access routes to Frio: 1. Directly across the narrow plume of sand to the SE tip of the cape. 2. Back up to the "yellow brick road" of Smith Street, following it around to the cape wall. 3. All the way back up to the surface of Meridiani, then around to the cape wall and down.
I favor the first, if careful inspection suggests the sand is crossable. Otherwise #2. #3 would only be attractive if we were in need of a gust cleaning.

Surge posts by Don & Kye moved to the Surge thread : http://www.unmannedspaceflight.com/index.p...0&start=300

Some nostalgy Oppy ?
Isn't it an origami hen you're folding here ?

http://marsrovers.jpl.nasa.gov/gallery/all...26P2417L2M1.JPG

Can any one guess where Oppy is going to move to after the Lyell layer has been sampled? Im itching to get a move on!

Well I was preparing a post saying that new driving targets downslope were selected on sols 1397 and 1398 when I realized that Opportunity actually moved from the site it was parked since sol 1382.
The driving took place on sol 1402 and it looks like it was almost a turn in place and the rover is now parallel to the slope and facing on the general direction of Cape Verde.



For the next target, a "drive direction" pancam mosaic was taken on sol 1403. Here are the pictures: http://marsrovers.jpl.nasa.gov/gallery/all...nity_p1403.html

... and here's a fish-eye mosaic made with some navcam pictures from sols 1402 and 1404.
Click to view attachment

Here is the complete panoramic view taken with the

R0 Navcam on Sol 1402 and Sol 1404.

jvandriel

Click to view attachment

Seems the rover is now sampling the very edge of the Lyell layer.
And one thing has struck me as odd. The blue berries. There doesn't seem be many of them in Smith.
But I recall the layer akin to Smith at Endurance had lots of berries embedded in it. The lower layers seem to have a lot more, but still its wierd.

Is this because of removal and deposition of the blue berries by denudation or is this a chemical problem.

> Seems the rover is now sampling the very edge of the Lyell layer.

Yup. The current target (this image) was named "smith_lyell_contact".

Edited: BTW, if anybody is interested, here's a "map" of the targets that have been imaged since the start of the plunge.
Click to view attachment

Yes, Tesheiner, I'm very interested, thanks for the target map!

Notable on that map is the pair of rocks/cobbles Kuenen and Jin, which appear quite different in colour from the rest of the slope. Here they are identified in James Canvin's Lyell panorama:
Click to view attachment

Indeed intriguing. Kuenen at first glance looks very much like a conglomerate (or perhaps a breccia)!

Thanks Eduardo,
To my eyes it could even be included (replace ?) your "Oppy route" for quite a while.
This is definitively a new fine perspective.

Brilliant! Makes sense of the whole thing for someone like me too lazy to figure it out from the new imagery.

I take climber's remarks and raise them by a power of TEN! Just what I've been needing, Tesh, me old matey!
Now if you could enlarge this a little more in plan view so we can recognize individual slabs in the pancams, and mark on them the RAT holes as we work down the Duck Bay transect, I will always cheer for Brazil in the World Cup!

Angular fragments would make it a breccia. As I recall (I don't offhand remember the rock's name or Sol) a glassy-appearing piece of brecciated rock was examined during the rim traverse, and some contributors here guessed it might be suevite (impact melt breccia). Let's hope for a closer look at Kuenen.

-- HDP Don

I simply wanted to add my praises, Tesh. Your latest work has been a very valuable resource.

I've just seen your pic Tesh and wanted to add my thanks. I didn't even realise all those rocks had been named, to be honest. If there's any justice there'll be a feature - or at least a rock! - inside VC named after you for all your hard work.

Thanks, all.


Actually I had my doubts if post it here or at the "route map" thread.
I got the idea to make it from an Alan's post (thanks mate!) at the beginning of the plunge. Since he didn't continue to update that one I did it by myself since then, including the features/targets imaged usually with the pancam like I do on the route map.

My complements to you Tesh.
Your map is certainly invaluable and impressive (it helped me get my bearings right).

I have wanted to see impact melt since we first landed on Mars. The matrix of the breccia is the impact melt, of course -- the clasts are pieces of rock that were caught up in the melt. That melt ought to give us a first-order feel for the gross composition of the target where the Victoria impactor struck. If the melt has remained generally unaltered, we have an important clue to the mineralogical nature of the surface 'way back when this hole in the ground formed.

This assumes, of course, that any piece of impact melt we find here is of local origin. As you are fond of pointing out, Herr Doktor, there are an awful lot of impact craters on Mars... *smile*...

-the other Doug

I thought that as a general rule impact melt was displaced at distance from the transient crater and lightly shocked ejecta from the deepest excavated layers was deposited in the crater vicinity?

Indeed that's what I think too. So if this impact melt is from Victoria the first thing we ought to wonder about is 'why is it at the rim.'

More likely it is from another crater. Or perhaps something happened during the creation of Victoria that this impact melt got embedded in the ejecta material which in turn was deposited at the present rim?

I liked the improved versions posted by others shortly afterwards, some with simulated rovers, more than mine so I figured it would be better to let them take over.

Impact melt can also form a lining within the crater. In smaller craters, a glassy lining is made up of impact melt. (Since we have never landed in or taken samples of the floor of a large lunar impact crater, we have almost no data on how abundant impact melts might be in the floor units of large impact craters.)

If this *is* local, I would imagine that the suevite was emplaced in the ejecta and has since eroded out of one of the prominent capes. Being harder than the surrounding rock, it would simply fall out of the cape structure and tumble down the inner slope of the crater.

-the other Doug

But we have studied and modeled the formation of large craters on earth. The floor of such craters often largely consists of impact melts and melt breccias. (N.B. Chicxulub is a large crater; Victoria is a small crater.) The deeper layers are typically in situ, whereas upper layers have fallen back from the core of the ejecta column. I would not describe any of the floor melt layers as "lightly" shocked, unless we are talking about rubble from the adjacent surface being washed in by an oceanic backflow. (Not applicable, probably, for Victoria.)

On sol 1409 Opportunity captured an MI mosaic of part of the Smith/Lyell contact. I think I can see some textural changes across the mosaic.
Click to view attachment
I think this MI mosaic imaged the area roughly outlined on this pancam.
Click to view attachment

jvandriel, I used your superb mosaic as usual, this time with addition of artificial colors:
Click to view attachment

Other Doug - All good, but let's remember that the piece of glassy-appearing brecciated rock in question (found along the rim of Victoria), let alone the piece of breccia that started this discussion, are not yet proven to be suevite (impact melt breccia) and that we have no idea where they actually came from (another suggestion was, as I recall, that the rock on the rim might be a fresh meteorite). Nevertheless, some useful generalizations have been made - that the furthest part of the ballistic ejecta blanket generally represents the near-surface material, and that as you approach the crater, more deeply excavated material is represented (it's ballistic path went almost straight up, and so it came almost straight down). This ballistic ejecta pattern, of course, ignores the fines that interacted turbulently with any vapor or atmosphere present and potentially went out extremely far as radial-flowing density currents (impact surge clouds). Also, the larger the impactor (and the softer the target), the more excavation energy is wasted in frictional heating, meaning that the crater formed is proportionately shallower, and that the quantity of impact melt formed is greater (that is, big craters are not as deep as and probably contain more impact melt than you might otherwise expect, especially in soft targets). A water-rich target might also favor the formation of impact melt (hydrous melts can form at lower temperatures than dry melts, in general), so martian impact cratering could have formed more melt than lunar impact cratering (or perhaps just bigger vapor explosions). Again, I'm not an expert, but have been trying to learn. So corrections would be welcome.

That said (and related to your earlier post stating a longstanding desire to see impact melt), where's all the impact glass that might be expected on Mars? Hydrous melts crystallize more readily than dry melts, water being a catalyst. That gets rid of glass. Quenched glasses also break down (weather) far more rapidly if minor water is present, especially it's acid and salty. So, perhaps that's where the glasses went on Mars as opposed to the Moon. On the other hand, glasses, being amorphous (noncrystalline), are difficult to detect spectroscopically, I'm told, and the spectra of "surface type 2" (Northern Plains, in general) are not a bad match for material rich in glass (or amorphous clays and/or silica formed from glass or another source). So my short answer is I don't know, but if the impact glass is indeed gone, water is probably to blame, one way or another. In this regard, geologically ancient glasses are generally lacking on Earth, owing to the abundance of water. Crystalline rocks last a lot longer.

First Doug, feel free to move this if it's again getting too general (and it probably is). I can't resist rambling - just ask any of my students.

-- HDP Don

Here's the part that I'm curious about. The Victoria impactor apparently slammed into an 800 meter thick pile of hydrated, sulfate-cemented, silicate sediment. Wouldn't the sulfate salts act as a flux, lowering the melting point and dissolving the silicates, then mechanically dispersing them as fine particles, as the impact cloud expands and cools?

Good discussion, wherever it eventually ends up "belonging"...

Yeah, I know there's no proof that we've actually seen a piece of suevite yet. I do sincerely believe that there must be a fair amount of impact melt on Mars, if only because, as HDP has pointed out, impact processes have likely predominated surface change on Mars for a long, long time. And Mars has been very dry (over much of the globe), to a pretty decent depth, for a long time, too. You'd expect to see less and less hydrous effects on the impact melts as Mars has become drier and drier, would you not?

Then again, no one really knows how much water is locked up in rocks and ices beneath Mars' surface. I guess it's possible that Mars retains enough subsurface volatiles to continue to preferentially degrade impact melts over other impact products, leaving much of the planet covered with ejected chunks of rock (some of it not even very shocked), and very little melt.

I don't suppose it's possible for Oppy to go visit this little chunk of what could possibly be suevite and take a real long sniff...?

-the other Doug

A mosaic of Opportunity's arm taken on Sol 1407

with the R0 Navcam.

jvandriel

Click to view attachment

CR - Vicky is a relatively small crater (smaller than Meteor Crater, AZ), the cratering didn't go all that deep, and explosive vaporization of hydrated salts may have greatly exceeded melting, if there was any. Impossible to know, and no close terrestrial or lunar analogs are available. Now it's all buried under material that caved in off the friable former walls of the crater, as the crater enlarged itself by slope retreat, and even most of that material is buried under dune sand (which may also cover ejecta or dusty surge deposits derived from craters younger than Victoria). I guess we are lucky that the upper cliff exposures are as good as they are.

-- HDP Don

Thanks. I guess I didn't say it very clearly, but the possibility of significant vaporization is exactly what I was wondering about. I understand that that this is a rather small crater, and that if any local impact melt existed, it would be buried.

Yesterday I was chatting with a colleague about MER and he claimed that MER-B (Opportunity) is dragging a wheel. I replied that he was mistaken and that only MER-A (Spirit) is dragging a wheel. Are all six wheels of MER-B still working?

Opportunity has a front right wheel STEERING actuator that is broken...i.e. it's stuck facing just about forwards. BUT - it still turns to drive the vehicle.

Doug

CR - That would probably depend on how "wet" (including ice) the area was at the time Victoria formed. Presumably, given its equatorial location and seeming high permeability, any ice (cryosphere) or brine horizon was buried more deeply than Victoria cratering ever reached, leaving salt dehydration as a source of vapor. Then we get into how to interpret the word "significant" and I won't hazard a guess. All I'll say is that the target rocks were quite weak and at least somewhat hydrous, and so probably were heavily disaggregated by the impact. That is, lots of sand blasting to flay your skin and relatively few big pieces of ejecta to hit you on the head. And that's just a guess.

-- HDP Don

Checked the PCDT web right now and Opportunity should be moving to another site/target on sol 1416.

Oppy appears to be doing a cloud imaging campaign, and there are many frames where you can see clouds, even through all the dust on the lens! Here are a few of the best frames, from 1413:
http://marsrovers.jpl.nasa.gov/gallery/all...26F0006L0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...26F0006L0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...26F0006L0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all...26F0006L0M1.JPG
I wish I could flat-field those things!

(Sorry for the distraction from the Mercury party! )

Excellent. I've always wanted to see more of the clouds, the forms they take and the ways they change.

By the looks of these images, these are the typical water ice cirrus clouds which migrate south for the winter. These ones are apparently moving from north east to the southwest
(following the local winds?)

Opportunity moved about 2m downslope during sol 1416.
Take a look to this rear hazcam picture. That's the rat hole made on the Lyell layer, which is now way behind the rover.

(Edited to point to a picture at the correct side of the planet.)

Thanks for the heads up, Tesheiner, but it sure is strange how much Victoria suddenly looks like Gusev!