Stardust Analysis Results, initial results for comet Wild 2, including organic compounds Options

[Guest_AlexBlackwell_*]

Coincidentally, the February 2006 issue of Meteoritics & Planetary Science has a special section entitled "Experimental Studies in Preparation for the Analyses of Samples Collected by Stardust."

[The Messenger]

Thanks Emily, This is great!

Zolensky continued by saying "we are not seeing phyllosilicates or carbonates" but that they are seeing some exotic minerals like vanadium-bearing osbornite...

Yes, this is 'astonishingly weird', but is it 'amazingly close to expectations'? What were they expecting? vandadium-bearing osborosilicates? Are we looking at Kuiper Belt stuff and/or cosmic dust and/or the shattered remains of a supernova?

The diversity of minerals alone suggest this comet is not an evolved body, but truly some kind of primal agglomerate...not a likely scenario for a life-bearing body, carbon or no carbon.

[Gsnorgathon]

You'll note from Emily's update:

The biggest challenge Zolensky faces is figuring out to what extent the Stardust samples were altered by their capture.

I'd guess that's the reason for no discussion of organics yet.

EDIT: Er, after getting to the bottom of that article... I'd guess that's the reason for not much discussion of organics yet.

[Guest_AlexBlackwell_*]

You'll note from Emily's update:
I'd guess that's the reason for no discussion of organics yet.

I guess that's why I think Oberg's Stardust-to-Enceladus-sample-return idea probably wouldn't work.

[The Messenger]

You'll note from Emily's update:
I'd guess that's the reason for no discussion of organics yet.

The biggest challenge Zolensky faces is figuring out to what extent the Stardust samples were altered by their capture.

EDIT: Er, after getting to the bottom of that article... I'd guess that's the reason for not much discussion of organics yet.

It is a little disquieting to read the aerogel contained organic contaminations to start with, and that contamination may have been introduced during disassembly. (Albiet at the detection levels they are working with, there will be an organic background.)

The article mentioned that some of the organics are inclusions. I guess the downside of the larger-than-expected particles is that much more heat was generated during capture: We were expecting Civics and ended up with cement trucks. The high velocities of both the Deep Impact and Stardust missions constrain the interpretive gains. A successful Rosetta mission will fill in some of the gaps.

[centsworth_II]

We were expecting Civics and ended up with cement trucks.

Hey, they got thousands of civics as well. Give them some time. A year or two for starters should do it.

[Guest_AlexBlackwell_*]

Hmm. Perhaps the element of surprise here is that olivine grains survived in an inner-system comet without alteration by water?

As Mark Peplow notes in the March 16, 2006, issue of Nature (excerpt below), it appears the refractories found in the Stardust samples were "supris[ing]" because many scientists, presumably the majority of the Stardust team too, view the X-wind model as "controversial."

===================

"The presence of CAIs was predicted by one controversial theory, however. The 'X-wind' model sees strong magnetic fields around the young Sun channelling heated material to the far reaches of the protoplanetary cloud. The Stardust results do not prove anything, but they certainly fit with the idea, says Mike Zolensky of NASA's Johnson Space Center in Houston, Texas, who is leading the mineral analyses.

"The other possible source of the minerals is another star completely. Once formed, the grains may have drifted through interstellar space for eons, before reaching our own Solar System and being incorporated into Wild 2. Zolensky says it is too early to know which theory is right. But Brownlee adds that measurements of isotopes in the grains could settle the question within months — such materials often bear a distinctive isotopic signature determined by their star of origin."

[Guest_RGClark_*]

As Mark Peplow notes in the March 16, 2006, issue of Nature (excerpt below), it appears the refractories found in the Stardust samples were "supris[ing]" because many scientists, presumably the majority of the Stardust team too, view the X-wind model as "controversial."

===================

"The presence of CAIs was predicted by one controversial theory, however. The 'X-wind' model sees strong magnetic fields around the young Sun channelling heated material to the far reaches of the protoplanetary cloud. The Stardust results do not prove anything, but they certainly fit with the idea, says Mike Zolensky of NASA's Johnson Space Center in Houston, Texas, who is leading the mineral analyses.

"The other possible source of the minerals is another star completely. Once formed, the grains may have drifted through interstellar space for eons, before reaching our own Solar System and being incorporated into Wild 2. Zolensky says it is too early to know which theory is right. But Brownlee adds that measurements of isotopes in the grains could settle the question within months — such materials often bear a distinctive isotopic signature determined by their star of origin."

Thanks for the info on the presence of the calcium-aluminum inclusions (CAIs). The isotopic ratios in such inclusions found in meteorites has been used to deduce the amount of radiogenic heating in their parent bodies and whether this would be enough to raise their interiors to the melting point of water. It would be interesting to find out what they find out about the isotopic ratios in the Stardust CAIs.
In regard to the CAIs it was found in some meteorites they had to be subjected to some episodes of remelting, perhaps in the range of 2 million years after they formed. Perhaps these heating episodes could be what also caused the crystalline olivine.
Incidentally, anyone know why the remelting episodes of the CAIs and the high heat required for the Stardust olivine minerals could not be simply due impacts?

posted May 31, 2005
Making Sense of Droplets Inside Droplets
--- The vexing presence of chondrules inside supposedly older calcium-aluminum-rich inclusions (CAIs) in chondrites makes sense if the CAIs were remelted.
http://www.psrd.hawaii.edu/May05/chondrulesCAIs.html

posted September 30, 2002
Using Aluminum-26 as a Clock for Early Solar System Events
--- Correspondence between 26Al and Pb-Pb ages shows that 26Al records a detailed record of events in the early solar system.
http://www.psrd.hawaii.edu/Sept02/Al26clock.html

In looking up images of CAIs and chondrules in meteorites I came across this:


"Image of chondrules projecting from the
surface of a chondrite. Chondrules make
up the greater portion of some chondrites."
http://web.pdx.edu/~ruzickaa/G410/Hewins/glos7.html

I was struck by the similarity to the spherules of Meridiani. They also are of the same size range, a few millimeters across. However, I wasn't able to find references that suggest they contain hematite.



- Bob Clark

[Guest_RGClark_*]

Thanks for the info on the presence of the calcium-aluminum inclusions (CAIs). The isotopic ratios in such inclusions found in meteorites has been used to deduce the amount of radiogenic heating in their parent bodies and whether this would be enough to raise their interiors to the melting point of water. It would be interesting to find out what they find out about the isotopic ratios in the Stardust CAIs.
In regard to the CAIs it was found in some meteorites they had to be subjected to some episodes of remelting, perhaps in the range of 2 million years after they formed. Perhaps these heating episodes could be what also caused the crystalline olivine.
Incidentally, anyone know why the remelting episodes of the CAIs and the high heat required for the Stardust olivine minerals could not be simply due impacts?
...

This article reports on research observing chondrules being created after the period when solar nebula was undergoing the high energy processes hypothesized for the origin of the chondrules. The scientists discovering these late chondrules propose instead they were formed by impacts. Then it may be as well all chondrules were formed by impacts. Note as well in the first image crystalline olivine is included in the chondrule:

posted October 21, 2005
Little Chondrules and Giant Impacts
--- Chondrules in metal-rich meteorites formed a couple of million years after most other chondrules, possibly by impact between moon-sized or larger objects.
http://www.psrd.hawaii.edu/Oct05/chondrules_impacts.html



- Bob Clark

[Guest_BruceMoomaw_*]

CAIs don't contain hematite -- the fact that they're spherical like the Blueberries is due to entirely different types of physical processes. (Specifically, CAIs are droplets of molten rock that resolidified in the early solar nebula; the main question about them is what heated them to that level. Blueberries, on the other hand, are made out of water-dissolved minerals that recrystallized in spherical form, possibly around a chemical ucleus.)

[Guest_RGClark_*]

CAIs don't contain hematite -- the fact that they're spherical like the Blueberries is due to entirely different types of physical processes. (Specifically, CAIs are droplets of molten rock that resolidified in the early solar nebula; the main question about them is what heated them to that level. Blueberries, on the other hand, are made out of water-dissolved minerals that recrystallized in spherical form, possibly around a chemical nucleus.)

To be precise, as explained in those links, CAIs are different than chondrules. It was the chondrules that I was comparing to the Meridiani spherules.
I'm not necessarily arguing the chondrules are formed like the spherules, not necessarily. I'm just intrigued by the similarity in appearance, and even their size. But as I said I looked up some references on the chondrules and none of them mentioned them containing hematite.
The prevailing view now is that Meridiani spherules formed by sedimentary processes. However, when they were first seen there was speculation they may have formed as impact melts.
I seem to recall some of the Meridiani spherules seemed to have distinct rims, like of some other material. Is this correct? If so, it is notable that an important feature of the chondrules is they also often have rims of a sedimentary material, but in this case phyllosilicates, clay.



- Bob Clark

[Guest_BruceMoomaw_*]

In the case of the chondrules, this is because their outer surfaces were dampened by water in the matrix of the carbonaceous material AFTER they became embedded in it as it formed.

[Guest_RGClark_*]

In the case of the chondrules, this is because their outer surfaces were dampened by water in the matrix of the carbonaceous material AFTER they became embedded in it as it formed.

I have no objection to that. Especially if such chondrules are found in the Stardust materials.


- Bob Clark

[nprev]

I am beginning to wonder if cometary olivine and other such minerals which are rapidly destroyed by environmental processes on the surfaces of planets are in fact truly primordial. I see no reason that such minerals could not be produced in abundance within supernova shells under certain circumstances. I assume that at least some of the Stardust investigations will include an isotopic ratio analysis of the samples whenever feasible or appropriate?

[ljk4-1]

Jonas Dino
NASA Ames Research Center, Moffett Field, Calif. March 29, 2006
Phone: (650) 207-3280/604-9000
E-mail: jonas.dino@nasa.gov

RELEASE: 06-19AR

STARDUST SPRINKLED OVER NASA ASTROBIOLOGY CONFERENCE

NASA's Stardust mission has energized the scientific community with new insights into comets and the formation of the solar system.

On Thursday, March 30, Dr. Scott Sandford, NASA scientist and Stardust co-investigator, will update Stardust developments at the NASA Astrobiology Science Conference, at the Ronald Reagan Building and International Trade Center, Washington. The plenary session is from 8:30 to 9:10 a.m. EST in the Reagan amphitheater.

"Preliminary examinations indicate that the Stardust mission is a great success," said Sandford. "It is clear that the mission returned cometary materials in the form of minerals, and we are finding organic materials associated with the grains."

"While it remains to be proven that these organics are of cometary origin, we are highly encouraged by the analyses thus far, and further analyses may revolutionize our understanding of these important and primitive materials," he added.

Launched February 7, 1999, the spacecraft's sample capsule successfully returned on January 15, 2006. Samples have been distributed to about 150 scientists around the world for study.

For more information about AbSciCon 2006, visit:

http://abscicon.arc.nasa.gov/