We're starting to get MI's in from the "scratch and sniff" stop on the Etched Terrain on the way to Erebus:

http://marsrovers.jpl.nasa.gov/gallery/all...47P2936M2M1.JPG

Similar to what we saw elsewhere here: blueberries eroding out of vuggy evaporite.

--Bill

Part of me hopes that its drastically different to Eagle/Endurance outcropping so that we can do some science with it ...but a little part of me hopes it's identical so we can save the RAT and make more ground to the big kahuna

Doug

Two thousand posts, Doug!
Have you realized that?

I should get out more

The whole site stats I like watching
Total Unique Topics 1216 Total Replies to topics 15168
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I'll post an image of stats to date elsewhere

Doug

I agree with Doug, we need to get moving to the next target and points southward, but since this is the first "major" outcrop of the Etched Terrain evaporite unit, it behooves us to pick up a piece, look at it with the handlens and thwack it with the rock hammer. _Any_ geologist would do that. We need to see _if_ there are differences. And she needs to look at the first "significant" piece of the "dark angular stuff" we've been seeing.

We've been travelling updip, and we are now several (hundred?) feet lower in the unit than we were. Seeing drastic changes will tell us a lot, as will seeing uniformity in the section.

--Bill

Basically - I'd have thought "right - this is the outcrop - have we actually covered some vertical range here - are we looking at something different - or is it similar to before" and actually - you could take the apxs spectra from here - and match it up with the ones from the crawl down Endurance and see how deep - if any - we are.

Then - if it IS something new - give it the works - and do so again at erebus. If it isnt - I'd be inclined to make only a vostok-like flying visit to Erebus - and skirt it's NE rim with a 180deg mosaic, before heading SE.

Doug

I didn't have data on the dip, Bill. Thanks for that. Even if the rocks have remained the same, we will have learned a lot just learning more about the thickness of the column of similar rocks. This may be a bit geologically arcane for this forum but I'd like to learn more about facies changes as well.

I've been meaning to ask you to comment in more detail about the "dark basal unit" you have been mentioning. I think I now see the connection you are making between the dark band at Erebus and the "angular fragments" Steve said will be a new target. As much as I'd love to see new rock layers, couldn't that "dark band" be a shadow?

CR, I don't know what the dip is here, last year someone produced a cross section that suggested it. It's speculative geology and not carved in stone...

I honestly don't know about that "unit that produces the dark angular fragments in the blueberry-basalt sand mix". Seeing those "D1-D2" dark areas in the MOC roadmap image and our peeks into Erebus makes me think they are indeed a dark rock and not a shadow. Originally I assumed that they were a shadowed bluff on the MOC image. I also jumped the gun speculating that this dark rock was at the contact of the blueberry sand soil and evaporite, so it was basal to what we've been driving upon.

I dunno exactly what it is, but it _is_ a new lithology that we are starting to see. Initially we noticed the small dark angular fragments in the dune troughs and now we're seeing larger dark chunks on the evaporite bedrock. The first big piece we mosey close to needs to be thwacked and looked at. I'll suspect that we will start seeing in-situ pieces of this dark rock and that contact will be somthing to look at.

Remember the geomorphology of this etched terrain: it is an ancient weathered surface of the evaporite unit that also consists of overlapping weathered ejecta blankets of old impacts. The closer we get to Victoria the lower (??) we'll be in the section and then we get to Vicky's ejecta blanket we'll be in an area of weathered material from a deep excavation.

Imagine that you are at an abandoned coal strip mine. You are ambling along looking at monotonous spoil piles of fragmented shale and sandstone. Every so often you see an interesting fragment. You come around a spoil pile and there is a highwall a few hundred feet away, and it looks interesting. You'll head to the highwall and look closely maybe you'll find a marine unit in the deltaic facies you've been in forever. Little signs like this let you piece together the history of the area.

A mundane example, but appropriate...

--Bill


PS-- save you a trip down the hall, no new Oppy images at JPL/MER site or the Exploratorium.

Is that a strange MI from Sol 546 or what ??

Yes!

New MI images for Sols 544, 545 and 546. Pre-brushed, brushed and RATted.

http://marsrovers.jpl.nasa.gov/gallery/all/opportunity.html

--Bill

http://marsrovers.jpl.nasa.gov/gallery/all...47P2936M2M1.JPG

The big difference I see is that that in previous RATings through "blueberries" there was often a visible separation between the "berry" and the surrounding matrix. I don't see any such separation in these latest images.

Here is a quick and dirty and bad stitch from Sol546 MIs : (until the professionals post their versions )

The spherules also seem to be smaller than those at Endurance and Eagle. There also seems to be greater variation in size to the spherules. Maybe the depositional environment here was not as stable as at Eagle and Endurance, with more variables being thrown into the spherule-making equation?

My sense, and it only a sense, is that there may also be a larger quanitity of the concretions in the matrix than would have been expected earlier in the mission.

My feeling too is that the size and distribution of the blueberries is quite different than what we've seen before. And some of the sliced berries are irregular in shape.

--Bill

I agree with centsworth_II, these berries don't seem to wear their rocky jackets of matrix around them. Maybe the matrix now is a different rcok material, or the concression mechanism is not the same (different chemistry here ?)
Pretty interesting stuff

Gentlemen, wouldn't it be equally teriffic if we continue to encounter the typical Meridiana stratum, as seems to be the case? Ie, doesn't flat strata strengthen the case for water? Of course I realize that volcanic ash fields, for example, can also be flat -- but residing in South Louisiana, I am here to tell you that if you want REALLY flat, water is your man.

Perhaps dark rock at D1/D2 will be entirely composed of spherule material.

http://marsrovers.jpl.nasa.gov/gallery/pre...3a/PIA05154.jpg

The hematite signal seen from orbit strengthens to the south.

Here is an Autostitch of the sol 546 rathole. I've flipped it 180 degrees to make it appear as if the sunlight is coming from the top, since that works best for my brain. (the cracks don't look like ridges.)

>There seems to be a higher concentration of hematite concretions than we have previously seen.
>They are more irregular in shape.
>Their size distibution is also more variable.
>There seems to be a population of very tiny ones and a separate population of diffuse hematite? concentrations.
>There are some rat dust agglomerations obscuring the view.
>There is a fine network of fractures permeating this rock.

Oh, and did I mention that it is nice to be on solid ground again? We are so fortunate to have found some rock once again.

Yeah, Cosmic, my brain likes that perspective better as well! One of the more intriguing things are those dark spots which have the same grayish tones as the spherules. Are these micro-spherules? Could they represent the nucleus about which the spherules (concretions) grew?

Mmmmh, it looks like a cake with cherries, raisins and so. Did not they said it was an icecream?

That is exactly where we are.

One scoop or two?

http://marsrovers.jpl.nasa.gov/mission/sta...tml#opportunity

--Bill

Bill: Sorry to get back so late to you on this. I know what you mean. I don't know what it is either, but obviously those dark fragments are coming from somewhere. Meteorite fragments? It's good to know we'll be "thwacking" them shortly. Also, it should not be too long before we get a good view of Erebus' edges. A new contact would be a dream come true.

Regarding ejecta balnkets, we really haven't seen any ancient ones, as far as I can tell, athough most of the bedrock has been covered. We really should have seen some evidence of them this close to Erebus and the others. The ejecta may have been eroded away. The sol 546 MIs were somewhat different, but they still looked like rocks from the original, calm sedimentary environment.

Is this getting fun, or what? I can't wait to see what's "round the bend."

It's getting interesting. I'm still looking/waiting for the holy grail of marker beds to help start tying things together. This is rather like the Pottsville Formation of north Alabama: essentially flat-lying, alternating beds of shale and sandstone.

--Bill

Sol 551 images (well, one MI) are up at the MER/JPL site. Looks to me like one of the dark angular fragments and seems to me to be quite interesting.

http://marsrovers.jpl.nasa.gov/gallery/all...D4P2936M2M1.JPG

--Bill

Yeah, I was hoping for more than one image, too. It's dark, fine grained, fractured, and a bit out of focus. Perhaps tomorrow. It's too small to RAT and probably too small to get good data from with the spectometers. Let's hope they find a "bowl" of them.

Beggars can't be choosers. This is our very first look at one of these mystery rocks and I'm happy for this preview. I'm sure that there are more MI's in the pipeline and they'll get posted next week.

I spot larger dark rocks on the evaporite "windows" off the road, I'll suspect that she's not going offroad to look at them (wise choice) and we'll wait til a dark rock happens to be on the path.

In the meanwhile, this sneak peek is interesting...

--Bill

From Squyres' 14Aug update:

The dusted RAT hole:


The dark, angular chunks:


Uodate at http://athena1.cornell.edu/news/mubss/ .

--Bill

This is the first opportunity we've had to MI these dark angular rocks and this is at a branch of the decision-tree to decide whether or not to investigate these rocks further.

From what I see already, these are interesting rocks:

http://marsrovers.jpl.nasa.gov/gallery/all...D4P2957M2M1.JPG

--Bill

In that image, the rock looks to be a breccia, which might suggest ejecta over meteorite.

Gray:

I see slightly water-altered vesicular basalt... ...so: Ejecta!

Bob Shaw

Given the rock types we've seen here, that is a reasonable conclusion. But the little voice in the back of my head says "not basalt", so I'll reserve judgement til we *thwack a couple more samples.

--Bill

Yes. It is interesting. Fine grained, but clearly not homgenous. I'm not sure I'd call it a breccia, but there are chunks. I suspect they will investigate them further, especially considering Steve Squyres' "surprise" 8/17 update.

" Oh, yeah, and the cobble we looked at with Opportunity isn't a meteorite, it's a martian rock... and one that's very different from anything we've ever seen before. Busy times..."
http://athena1.cornell.edu/news/mubss/

Bill: I think I hear that little voice, too. Let's hope they thwack them some more.

Stitch of Sol556 MI pictures

Geo-trivia...

I wonder why they are calling these "cobbles" when they would normally be called gravel or pebbles? Then again, one might wonder why we refer to the aeolian structures as dunes when they might actually be ripples.

These dark angular rocks of interest that we are initially looking at are below cobble-size (64mm-256mm) but I think they have been looking off the planned route and seeing larger rocks of interest, so we may be looking at actual cobbles soon. We "caught the first two minnows" to determine whether or not closer examination was warranted.

It looks like she is doing an eastward jog to the evaporite bedrock of the Erebus Highway so there are going to be plenty of interesting things to look at.

--Bill

No new info on the cobbles. Doug, could you ask Steve about these?

I have a new theory about the appearance of the rock in this RAT hole.

We're approaching Erebus, right? Erebus is a bigger crater than Victoria, although a lot older. In fact, it seems likely that Erebus was formed before the waters receded.

That would mean that Erebus ejecta would have been scattered on top of an existing evaporite layer, only to become embedded in later evaporite layers.

I think the dark cobbles we've been seeing, increasing in population density as we approach Erebus, are in fact the remnants of Erebus ejecta that have eroded out of the evaporite. I also think that the dark clasts visible in these MIs are small-grained ejecta particles that became embedded in the evaporite as it formed around it, during evaporite deposition eras that post-dated the Erebus impact.

And I think these materials may represent the sub-floor material that lies below the evaporite layer.

What do y'all think?

-the other Doug

I tend to agree, Doug^2. And remember that we are seeing a dark unit in the walls of Erebus which is clearly the source of the dark angular chunklets. I also see the dark unit in a smaller crater along the way, so we don't need to risk detouring across Erebus. I am especially interested in seeing the contact between the evaporite and this dark rock.

Not only do we have the excavation of Erebus, but also of "Terra Nova", a larger crater predating Erebus.

Have we heard anything about the minerology of the dark rock she Mossburged?

--Bill

The dunes are stratigraphically higher than the evaporite, but we dont' know if the dunes are "original" in this area or are sand that's windblown hundreds or thousands of kilometers across Meridiani.

We dont' know what's missing from on top of the evaporite, there may/probably-were other layers that weren't consolidated enough to survive.. the cobbles may be from within or on top of that/those layers.

The evaporite is stratigraphically higher than "XXXX", where XXXX is a softer layer than the evaporite, maybe unconsolidated, that refuses to form outcrops in craters like Endurance or Victoria.

The "XXXX" unit is on top of what appears to be another evaporite layer, judging from a crater some few tens of km to the southwest <I think> with a bench of what looks like more evaporite halfway down, then more unconsolidated layer below the bench down to the bottom, which is occupied by a gorgeous dune-network that puts the one in Endurance to shame.

Below that, only Mars knows, for now.

The cobbles well could be ejecta from Victoria and/or Erebus, deposited on the dunes or now missing higher layers and "lowered" down onto the evaporite over time. I was *really* frustrated Steve declined to mention them during the briefing and didn't get Q&A'd afterwards.

The dunes are the recent/current part of the section; I barely consider them "rocks", but a soil or regolith cover. If this were a terrestrial geo-map, the dunes unit would be colored yellow and labeled "Qal"...

But they are recent, ephemeral and unconsolidated. I imgine that the source area is to the NW, upwind of the prevailing winds. The prevailing wind direction likely shifts with polar drift/precession/orbital changes, which change the climate over many kiloyears. Remember, on the large scale, weathering erosion and deposition on Mars work over timeframes of 10's of thousands of years.

I dunno what the stratigraphy of the area is; we've only seen a couple of small windows and need to look at more roadcuts. I've been meaning to search the MOC/Msss archives and piece together a regional map of the area, but haven't, yet.

What image was the "crater some few tens of km to the southwest" on?

--Bill

"What image was the "crater some few tens of km to the southwest" on?"

I've got that @#$@ image on a hard drive on a computer that's not currently running (NT format), and on any of some 50 CD's of minimally sorted and undocumented images and files, and my netting computer is Winbloat 98se.. so It can't read that drive. I gotta find the time to get the other puter running again and files consolidated so I can find things....

Just think of me under a pile of CD's and books and LP's and VHS and.... with one mummified hand sticking out into the air....

I'll try to find that image.. it's not a huge crater.. 5 km maybe.. but very neat.

OMG, I see that others are experiencing bouts of Image Inundation, too. I've got many, many images that "I remember..." or that I come across and have no idea specifically which image it is...

Early on, a year and a half ago when this was to be a 90-day mission, I started renaming "nifty" Rover images in the "oppy0001.jpg" format and now I have hundreds of images with a non-standard filename.

If you can't fine it easily, don't sweat it. It'll turn up...

--Bill

I have a pdf presentation entitled "Mars Express OMEGA and Opportunity Coordination"
by R. E. Arvidson that includes several maps/images of the Opportunity general area, along with interesting figures about geological composiiton.

I have no idea where I downloaded it from

If anyone thinks it can be helpful and can't find it, I can email it (it is too big for posting here, 19 Mb)

Edit: Ok, I have cannibalized the pdf for this MOLA map, I hope it is useful

It is on this same forum: http://www.unmannedspaceflight.com/index.p...findpost&p=7651

Cool interesting read

On a side note just ordered Steve's book "Roving Mars" cant wait for it to get here!

Thanks

John

Thank you Tesheiner !

Association of Memory Challenged Forum Users

Nice relief map. It really puts Victoria crater into perspective. I wonder if there is a point in the area high enough to allow us to see to the huge (relatively speaking) crater to the SE?

Back a month ago, Bill Harris asked ..."What image was the "crater some few tens of km to the southwest" on?"....

I was referring to an image of a crater in Meridiani with a bench of probable evaporite rock halfway down.

Finally found it. I don't have the location, but that should be findable. It's well outside the main pre-landing mosaic of the Meridiani target ellipse, so it's certainly not identical in geology to the immediate vicinity of Eagle and Endeavour and Victoria, but I think it makes an important point about hard and soft layers in Meridiani Planum.