[X] My Assistant

[Burmese]

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.

[Guest_BruceMoomaw_*]

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?&...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.

[dvandorn]

...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.

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