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Posted by: Burmese Oct 24 2005, 03:25 PM

According to Steve Squyres' latest journal entry, Opportunity is now seeing virtually -no- blueberries in the surface matrix anymore.

"...On top of that, Opportunity has stumbled onto something really new and different lately... the blueberries seem to be gone!..."

And a theory:

"But one possible guess at this point is that we have moved "up section" in geologic terms -- to rocks that are higher up in this stack of layered sediments -- and that the rocks at this level never experienced the concretion-forming process. It's an interesting hypothesis with interesting implications, and it's also one that could explain a few other odd things we've been thinking about ever since Eagle crater"

Looks like Oppy will stop for some intense IDD work in the next day or so.

Posted by: Tesheiner Oct 24 2005, 03:37 PM

Too early I think.
Steve said: "We're not jumping to any conclusions, but everybody is itching to get the IDD onto this stuff as soon as we get the chance."

Imho, that chance will be once Oppy touches hard rock again, not earlier.

Posted by: Tman Oct 24 2005, 04:01 PM

Wow, it seems Erebus as the (maybe) highest place around Oppys landing site could be more interesting as ( I ) expected.

Posted by: paxdan Oct 24 2005, 05:07 PM

I wonder if there is a correlation between the lack of berries and the size of the ripples. Perhaps the reason the terrain aroud Eagle and endurance was, for the most part, ripple free was the because the berries prevent ripple formation. As the berries decrease in number/size and dissapear the fines can become sculpted into bigger and bigger ripples.

Posted by: Richard Trigaux Oct 24 2005, 06:37 PM

And the terrain becomes more dangerous, alas, with big ripples.


The change is not only ripples, it is the overall etched terrain.

Posted by: Bill Harris Oct 24 2005, 06:55 PM

Hmm, one gets so accustomed to seeing blueberries _in_ the evaporite matrix that one doesn't notice when they are _not_. I did a quick reality check and looked at the past several Sols of Pancam images of bedrock, and I see blueberries in the sand, I see blueberries lying on the bedrock, I see rough erosional surfaces on the bedrock, but I can't say that I see blueberries within the bedrock. At least, so it looks with these Pancam views and not an MI closeup.

Another piece of the puzzle: look at Doug Ellision's color image along the Four Lane at http://www.unmannedspaceflight.com/doug_images/erebus_3.jpg . I was planning to mention the color change in the dunes: instead of being blueberry blue, they now have a tinge of evaporite rust. Which may or may not mean anything, but we'll see if this puzzle piece fits...

--Bill

Posted by: CosmicRocker Oct 25 2005, 05:59 AM

Wow, that took me by surprise, too. I looked back through my image archive to try to pin down the change. We have good observations of tiny berries in the rocks up until Sol 609. There could possibly be some in the rocks observed right up until sol 617, but the imagery is not optimum for such observations. I can't say a lot, but it cetainly seems that the change from small berries to no berries occurred quickly, and recently.

As one not afraid to go out on a limb with an hypothesis, here is my best guess as to where this transition may be. On sol 617 Opportunity captured this navcam image of a contact while climbing up-section.

The full size image is here.
http://marsrovers.jpl.nasa.gov/gallery/all/1/n/617/1N182959987EFF62TOP1600L0M1.JPG

The layering in the lower part of the image is clearly different from that in the upper part. This looks like a significant contact to me. I can't imagine they will not go back to investigate this transition. I should say, they'd be crazy not to, unless there is a more convenient location to investigate.

Posted by: Bill Harris Oct 25 2005, 09:11 AM

You-gottit, CR. I'd guess that this contact was reached Sol 215-ish, and Oppy traveled more or less along the line of this contact for the next few Sols. I think the contact was where the beds started to be finely laminated. Attached is a color image from Sol 618 showing laminated beds with an apparent unconformity/crossbed.

Moving topographically higher, this may may tie the paleo-meridiani playa to the shallow groundwater berry-concretion process. The lower (strat- and topo-) parts were more often saturated than the higher ground "back then".

--Bill

Posted by: CosmicRocker Oct 25 2005, 07:37 PM

No doubt about it, the sol 617/618 outcrops were extremely interesting. I may have gone overboard a bit, suggesting they need to go back there for more investigation. I'm pretty sure that won't happen, but I really would have liked to see more close-up imaging around there.

I don't know if that contact is where the concretions disappear, but it has to be nearby. This area seems to have a lot going on, stratigraphically and structurally. Some places are really jumbled, and may indeed be impact ejecta. I agree though, that a change like the disappearance of the berries potentially has important implications regarding the paleoenvironment and/or the subsurface alteration processes. It sure could be an indication of a paleo-water table.

Posted by: ElkGroveDan Oct 25 2005, 07:43 PM

Good eye CR. I am in total agreement with you.

Posted by: ElkGroveDan Oct 25 2005, 07:49 PM

Perhaps, but it's possible we will encounter this same contact zone on the other side of Erebus as we head out of town.

Posted by: Burmese Oct 25 2005, 08:17 PM

One would think that the science team would -really- want to use the IDD on an area where they can see this up-section change. Indeed, while poking into Erubus itself might show some layers that correlate with those at Endurance, discovering a layer above all that would seem to me to be a higher priority. They know they are on fairly high ground in the area and I would think they would be fearfull of passing it and descending (as they head towards Victoria) before they have a chance to fully analyze the new strata.

One also wonders if they didn't connect all the dots before they had passed beyond the transition zone. I can just imagine the daily meetings now as the tug-of-war over driving versus IDD work on this new strata are hashed out.

Posted by: Bill Harris Oct 26 2005, 01:11 AM

This area of the north rim of Erebus is darn interesting. Anytime you start seeing changes in the lithology or stratigraphy over a short distance means it's time to look closer. Thus far, we seen the weathering rind, larger and more numerous "cobbles" (the dark angular pieces that I rant about), a decrease in Blueberry size in the ripple sand, Blueberries that are in the 10-12mm size range, the change in the Blueberry distribution in the evaporite matrix, a change in the bedding of the evaporite, those circular fractures in the evaporite plates and a host of other things. I realize that Oppy needs to get to Mogollon quickly, but there are lot of changes that should be looked at as we move on.

One thought, and not rtying to toot this horn: could the contact that CR noted be a "brine splat" feature? Just a thought...

--Bill

Posted by: CosmicRocker Oct 26 2005, 04:21 AM

You know, I started thinking about that on the way home from work tonight. The Erebus impact is likely to have uplifted the local stratigraphy, so Opportunity might encounter a stretch of down-section travelling as it leaves Erebus, before getting back to the regional up-section trend. There is a risk though. If the drifts are obscuring the section on the way out of Dodge, we may never see it. Then again, we should be treated to an excellent vertical section at the Mogollon Rim site.

I'm sure they were tempted to slow down and "smell the roses" on sols 617-618, but as has been previously pointed out by SS and others on the team, a complex mission like this requires making many compromises. I won't presume to second guess them. They are very likely at least several steps ahead of us when it comes to interpreting this stuff. This step-up is just the most recent of many up-section climbs made on the southward trek, especially since approaching Erebus. This last one just seemed significant because it appeared to corellate with the loss of the berries and it displayed textural changes as well. I'd have to suspect we are significantly up-section from Eagle/Endurance.

Posted by: BruceMoomaw Oct 26 2005, 06:08 AM

As far as I'm concerned, the single most intriguing mystery left to us by the rovers right now is: what created the Blueberries? According to an upcoming poster at the Fall 2005 AGU meeting ( http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm05&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm05%2Ffm05&maxhits=200&="P21A-0140" ):

"There are two main possible reaction sets for formation of the Blueberries that are consistent with all current data:

"(1) Local concentrations of organic matter (pre-biotic or biotic) formed reduction spots in which a small amount of Fe3+ either in solution or from evaporite mineral salts, was reduced to Fe2+ and then diffused radially to form an iron oxide nodule by reaction with inwardly diffusing dissolved oxygen.

"(2) Similar local concentrations of organic matter could also have engendered sulfate reduction and consequent outward diffusion of dissolved sulfide reacted with iron in solution to produce an iron sulfide nodule, subsequently oxidized in situ to hematite (maybe via goethite)."

Organic matter. Well, well. It sounds too good to be true, but so far I haven't run across any alternative explanation proposed for the damn things anywhere on the Web -- and not for lack of looking.

Posted by: Bill Harris Oct 26 2005, 08:21 AM

Erebus may be up section, but OTOH, it may be down section. Or we may be "across section", looking at a facies change. We're trying to figure out a complex geology on what is essentially an initial walk-though of the site. But those guys in the left seat have prioritized getting to Mogollon and this feature is not a big enough blip to warrant several Sols of IDD work. I think that the "roadcut" at Mogollon will answer a lot of these questions.

Darned if they do, darned if they don't. When they stop and do a scratch-and-sniff at every interesting rock, we clamor go, go, go to Erebus; when they get going, we say stop, stop, look at that.

The Blueberries are a mystery wrapped in an enigma. My first thought at Eagle crater was "tektites or lapilli". Then it looked like they were a lag weathered out of hematite concretions in an erodable evaporite. But there are so many questions about their genesis and distribution that we'll have to wait for more pieces of this puzzle. The organic source noted by Bruce has great merit.

--Bill

Posted by: Tesheiner Oct 26 2005, 08:53 AM

I agree 100%.

Posted by: Myran Oct 26 2005, 04:31 PM

Thank you for posting that information BruceMoomaw.
"It sounds too good to be true"
It certainly are one amazing find - if confirmed - but its organic chemistry and not the 'L' word so I wont run around waving my arms in the air just yet.

Posted by: dvandorn Oct 26 2005, 06:08 PM

Hmmm... spherical concretions occur in lots of places here on Earth, too. I guess the first set of questions to ask includes the following:

1) Are there any terrestrial concretions that display similar chemistry, i.e., hematitic?

2) If the answer to the above is Yes, is there an accepted theory that organics played a role in their formation?

I know, I know, the Apollo 16 lesson is learned well, here -- that assuming terrestrial-like processes to explain observed phenomenah on other worlds can lead you down the wrong path. But if we're talking about organics here, we need to at least compare the situation at Meridiani to anything and everything even remotely similar in our terrestrial experience.

-the other Doug

Posted by: TheChemist Oct 26 2005, 08:58 PM

Here is an article that explains how organics can reduce hematite (as in the first possible reaction set for formation of the Blueberries posted by Bruce) :

"Surface stabilization of organics on hematite by conversion from terminal to bridging adsorption structures"
Geochimica et Cosmochimica Acta, Volume 67, Issue 5, March 2003, Pages 1055-1063
by Michael A. Henderson.

The reaction studied in the above article is : CH3OH(g)+Fe3+-O2−-Fe3+→H2CO(g)+H2O(g)+2 Fe2+
Hematite is reduced by an alcohol (methanol) (Fe3+ --> Fe2+)

Here is some relevant literature on hematite formation :

Hydrocarbon related bleaching of strata and hematite deposition in red beds at Moab, Utah: a possible analogous process that formed bright layers and hematite deposits on Mars
J. Ormö and G. Komatsu, Proc. Lunar Planet. Sci. Conf. 34th (2003) Abstract #1356.

Meridiani Planum hematite deposit and the search for evidence of life on Mars—iron mineralization of microorganisms in rock varnish
Icarus, Volume 171, Issue 1, September 2004, Pages 20-30
Carlton C. Allen, Luke W. Probst, Beverly E. Flood, Teresa G. Longazo, Rachel T. Schelble and Frances Westall

Laboratory simulations of Mars aqueous geochemistry
Icarus, Volume 170, Issue 2, August 2004, Pages 404-423
Mark A. Bullock, Jeffrey M. Moore and Michael T. Mellon

Geological features indicative of processes related to the hematite formation in Meridiani Planum and Aram Chaos, Mars: a comparison with diagenetic hematite deposits in southern Utah, USA
ICARUS 171 (2): 295-316 OCT 2004
Ormo J, Komatsu G, Chan MA, et al.


Diagenetic hematite and manganese oxides and fault-related fluid flow in Jurassic sandstones, southeastern Utah
AAPG BULL 84 (9): 1281-1310 SEP 2000
Chan MA, Parry WT, Bowman JR

Edited to add a couple more references.

Posted by: CosmicRocker Oct 27 2005, 04:24 AM

Organic matter certainly could create locally reducing conditions that would mobilize iron ions. But I'm not certain that organic matter would be necessary to create hematite concretions. I don't know what the oxidation state of the Meridiani sediments was at the time they formed, nor when the concretions formed, and that is critical to what happens later. Iron ions are relatively soluble in water when they are in the chemically reduced Fe+2 state, and pretty much insoluble when in the oxidized Fe+3 state.

Oxidation-reduction (redox) reactions are responsible for much of the secondary, iron mineral redistribution on earth. I've seen many examples of hematite concretions that formed around crystals of iron sulfide or other reduced iron minerals. They are often rounded but irregular in shape; but there are examples of very round and regular ones also. In these cases I think the concretions are formed by the diffusion of oxygen into the reduced environment around the sulfides, eventually converting them to iron oxides.

As I understand it, the early atmosphere on earth was chemically reducing, and the very early oceans were loaded with soluble, reduced, iron ions (Fe+2). Even after life and photosynthesis began, it took a long time before oxygen accumulated in the atmosphere, because initially most of the photosynthetic oxygen produced was consumed in the oceans, oxidizing the Fe+2 ions and precipitating vast quantities of Fe+3 as Fe2O3 (hematite), thus forming the amazing banded iron formations of the Precambrian period. I'm sure the actual reaction mechanisms might have been a bit more complicated, perhaps with a goethite or other precursor mineral. The main point is that the young earth had a lot of soluble, reduced iron available. So may have Mars, and that may have resulted in the precipitation of reduced iron species in the sediments, especially if the conditions were arid, or there was a lot of sulfur around.

If the early conditions on Mars were reducing, as they were on the early earth, there may have already been reduced iron minerals in the young Meridani sediments. They could have been oxidized later as the Martian atmosphere slowly became more oxidizing. It seems that such a scenario would eliminate the need for local concentrations of organic matter to reduce insoluble Fe+3 in order to mobilize the iron for diffusion. It seems that we only need a relatively homogenous distribution of small, iron mineral crystals in the sediments under reducing contions as a starting point. Then slowly and uniformly change those conditions to a moderately oxidizing state to create those lovely and uniform concretions known affectionately as blueberries.

Sorry about the rant folks, but Bruce started it. The diverse manifestations of redox geochemistry have fascinated me for much of my life. I worked on iron formations as a grad student, and my first real job was exploring for roll-front uranium deposits. Later, I studied huge redox interfaces that draped oil and gas deposits. It's a fascinating subject, and it gets more fascinating when you throw in the unknown or poorly known conditions during the early history of a planet. This stuff is really fun!

Posted by: jvandriel Oct 27 2005, 10:32 AM

A panoramic view of bedrock and Blueberries around Erebus.

Taken on Sol 616 with the R6 pancam.

jvandriel

Posted by: TheChemist Oct 27 2005, 10:46 AM

CR, I agree that organics do not appear to be necessary, a reducing spot is all that is needed to start either of the
two working scenaria for blueberry formation put forthin Bruce's post.
Maybe organics are implicated because people would prefer to find a scenario that
explains both the formation of hematite concretions AND the lack of organics on the surface ?
That would be simpler and more elegant

Rubbish. Given your background you should apologize when NOT expressing an opinion on such matters

Posted by: RNeuhaus Oct 27 2005, 02:10 PM

TheChemist and CR: Your comments are very interesting and I enjoyed reading it.

About the picture's post by Jvandriel: The many small stones alike on the bedrocks aren't blueberries? These are the rest of broken stones due to the age (aeolian and water erosion).

Rodolfo

Posted by: Bill Harris Oct 28 2005, 10:51 AM

CR makes a good point and it is a plausible explanation for the origin of the Blueberries. My own "day job" involves the prevention of acid mine drainage and bacteria can accelerate the breakdown of iron sulfides into soluble iron and sulfates. There are bacteria that metabolize the Fe+2 iron and leave the Fe+3 iron and others that feed on sulfates. There are types of terrestrial bacteria that utilize iron and sulfur so it is quite possible that this class of critters may have been on Mars.

Did we ever hear more about the composition of the "cobbles" (the dark angular chunks of my sometimes rant) that Oppy MI'd and MB'd on the Erebus Highway? I recall SS saying something about "new and interesting", then nothing. They may be basalt ejecta, but my little intuition voice says "massive hematite". And now that we have been seeing larger pieces of this material on the easy-going bedrock paths, I wish we'd stopped to take a closer look...


--Bill

Posted by: CosmicRocker Oct 29 2005, 05:52 AM

I don't know, Bill. It really is curious that we haven't learned more about the interesting, dark cobbles. I think SS mentioned in a previous update that they weren't meteorites, but that was it. I really would have expected there to be more investigation of them, especially some of the larger ones Opportunity has passed by.

All I can guess is that they figured out what they are in the initial investigation a while back, and they decided to only tell us what they are not. If they are from that apparently darker layer, we should learn more when Opportunity gets to the rim. If the dust storm doesn't interfere, that could be within the week.

Posted by: Bill Harris Oct 29 2005, 02:36 PM

I don't think that this is A Great Conspiracy or an ESA datahoard. They have initial ideas on the strat/lith of this area and the cobbles are the key, so they are likely waiting for more data at Mogollon. Heck, they're paying for this ride, so I'll go along.

I've been looking at bedrock pics from Sol-One and the conclusion I've reached is .

--Bill

Posted by: CosmicRocker Oct 30 2005, 06:32 PM

I wasn't implying any kind of conspiracy, Bill. Sorry if it sounded that way. I only meant they haven't told us what they think it is yet. That's pretty standard. They usually don't divulge everything they are thinking, and with good reason.

Posted by: Phil Stooke Oct 30 2005, 06:48 PM

CosmicRocker said:

"All I can guess is that they figured out what they are in the initial investigation a while back, and they decided to only tell us what they are not."

I think it's much more likely that they have NOT figured out what they are. The cobbles are clearly different, but the team doesn't understand them yet. They need more data, which might be found at Payson. There has been no shortage of discussion of different rock types at Gusev in recent months.

Phil

Posted by: Bill Harris Oct 30 2005, 11:14 PM

I wasn't seriously thinking anything conspiratorial; I was being light. They aren't publically going into wild speculation, although a lot of ideas have probably been tossed about over coffee. Or whatever they drink in Pasadena...

--Bill

Posted by: ElkGroveDan Oct 30 2005, 11:22 PM

Those under 30 are drinking iced mochas, the ones between 30 and 40 are drinking low-fat lattes, the ones between 40 and 50 are drinking flavored coffee, the ones between 50 and 60 are drinking decaf, and those over 60 are drinking regular coffee.

...since you asked.

Posted by: CosmicRocker Oct 31 2005, 06:15 AM

You're absolutely correct, Phil. It could very well be that they haven't figured out the dark rocks out yet.

I know, Bill. I was only making sure others didn't think I was trying to suggest a conspiracy. You and Phil are both correct. They are only trying to refrain from speculation.

That was pretty funny, Dan, and I think pretty accurate across the board. According to your theory, I am old beyond my years. I belong in the decaf crowd, but prefer regular.