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Posted by: paulanderson Feb 21 2006, 06:17 PM

I thought the analysis results, as they come in, deserved their own thread. I'm interested in how these findings relate to the "weird crystals" found and reported on in the previous Nature article.

A couple more updates, from Space.com and MSNBC:

Stardust Mission Yields Ancient Comet Dust
http://space.com/scienceastronomy/060220_stardust_update.html

Comet Dust Sparks Scientific Intrigue
http://www.msnbc.msn.com/id/11460590

"The early results reveal that the 4.5 billion-year-old comet contains iron, sulfides, glassy materials, olivine, and what the scientists termed potentially interesting isotopic traces. They believe that these materials were also available during the formation of other objects in our solar system.

What's even more amazing is how well the first round of analysis is matching expectations. Brownlee and other Stardust scientists are holding back their first formal reports for a scientific meeting in Texas next month — but during Monday's news conference, Brownlee said the samples studied so far contain iron sulfides and glassy material such as crystalline silicates. Those ingredients are found in meteorites as well.

Later, Brownlee told MSNBC.com that there were preliminary indications of organic compounds, based on telltale infrared readings. He cautioned that the initial indications were tentative and could still be traced to contaminants.

In the weeks and months ahead, Sandford and his team will be analyzing the types of carbon found in the samples — not only to trace the organics, but also to determine whether such compounds predated the formation of the solar system."

Posted by: The Messenger Feb 24 2006, 08:35 PM

So are the early results weird, or is it amazing how close they matched expectations

Is the language of science so inprecise that astonishingly weird means the same thing as amazingly close to expectations? Is it astonishingly weird that the initial results are amazingly close to expectations, or were they amazed to expect such astonishingly weird results?

Posted by: paulanderson Feb 27 2006, 01:45 AM

Another article also, from Discovery Channel:

Comet Dust Has Hints of Organic Matter
http://dsc.discovery.com/news/briefs/20060220/stardust_spa.html

Posted by: edstrick Feb 27 2006, 07:18 AM

"Is the language of science so inprecise that astonishingly weird means the same thing as amazingly close to expectations? Is it astonishingly weird that the initial results are amazingly close to expectations, or were they amazed to expect such astonishingly weird results? "

This is not the languate of science. It's the language of press-release, reporters, and off-the-cuff scientists trying to 1) give something utterly esoteric simple comprehensibility, and 2) boost public enthusiasm for the discoveries.

The "dirty snowball model" has been widely trumpeted as "overturned" but it's long if ever that the real "best consensus understanding" of a comet's nucleus was like a hard-packed re-frozen snowball with dirt.... that phrase has been an over-familiar "quick and dirty" descriptive phrase that took on a life and a pseudo-scientific reality of it's own.

Posted by: Phil Stooke Feb 27 2006, 02:02 PM

Right on, edstrick!

Phil

Posted by: The Messenger Feb 27 2006, 03:47 PM

Well, they have my attention. I think if you attach an excited London'rs voice to the first article, and a "Hell, we already knowed that" Texas drawl to the second article, you can see the unexpanded truth is somewhere in between.


True, but for the decades leading up to the comet chasing missions (Borelly, Haley) Zwicky's dirty snowball WAS the prevailing model. In any case, the moisture content in Tempel 1, and likely many comets, is much less than expected, and if you could tell Zwicky the predominant material blasted from the face of a comet was fine dust and iron rich clays, he would roll over in his grave. The "dirty snowball" model as originally envisioned has been overturned, but for those following the science closely, this happened about a decade ago.

I think it is very legitimate, at this time, to rise the question: If we need an explanation for why the earth has oceans, the collision of objects like Saturns icy moons, rather than comets as we now know them, seems a little more likely. True, the comets we see may have once been much more like these icy moons, boiling off surface ice over millennia of close encounters with the sun.

The astrophysical sciences are being rewritten, and it is fun to be part of the process.

Posted by: dvandorn Feb 27 2006, 11:48 PM

Very provocative... I'm going to respond to this over on the Moon board, I think, for reasons that will become clear when y'all get there...

-the other Doug

Posted by: paulanderson Mar 7 2006, 01:05 AM

Another article:

New Evidence Life on Earth Began in Space
http://www.news.com.au/story/0,10117,18360930-2,00.html

"SCIENTISTS examining the first dust samples collected from a comet have found complex carbon molecules, supporting the theory that ingredients for life on Earth originated in space."

I know, not a science journal article this time, but worth posting I thought. We will know more very soon now anyway from the LPS conference this month.

Posted by: AlexBlackwell Mar 7 2006, 01:47 AM

paulanderson, since I no longer post at the Space.com discussion boards, I'm glad that you can relay some of the references that I post here (e.g., Mars methane). And you even preserve my anonymity

Posted by: paulanderson Mar 7 2006, 02:48 AM

Do you mean the recent clathrate abstract? I couldn't recall where I had first seen the link posted before (sorry), but I found that I still had the link bookmarked (I actually do normally post a mention if a link, etc. is referenced from a particular person). I remembered it when I saw the other photolysis abstract that I posted.

Why did you stop posting there, if I may ask? I still do, but not as much as I used to, partly just time-wise. In terms of Mars coverage in particular, I do prefer this forum; more up-to-date with less "intense" debates (in a negative way); the people here take their Mars studies seriously and it shows. Silylene is posting here more also now I see, good!

Posted by: paulanderson Mar 7 2006, 07:46 AM

Stardust news conference on March 13:

NASA Announces First Stardust Comet Sample Results
http://www.nasa.gov/home/hqnews/2006/mar/HQ_M06040_stardust_results.html

Posted by: The Messenger Mar 7 2006, 04:50 PM

PAHs (Poly-Aromic Hydrocarbons) are complex, and would be "Amazingly close to expectations", and progenitors to life on Earth. DNA with a negative twist would be "Astonishingly weird" but not close to expectations. I suppose it could be "Astonishingly weird" if PAHs were postitively identified, because the identification of cosmic PAHs is tentative. (Yes/No?)

Posted by: AlexBlackwell Mar 7 2006, 06:48 PM

Despite a few good posters over there (e.g., JonClarke, silylene, borman, CalliArcale, Yevaud, shuttle_guy, etc.), the place was getting a little too kooky for me. And moreover, Space.com seems more concerned with keeping posters, no matter how stupid/loony/crazy they appear to be, than anything else. Doubtless this is for commercial reasons (i.e., for the sake of keeping eyeballs on their website), which I understand, but it's a little too freewheeling for me. Also, the Great Big Crash, which destroyed a large chunk of history, didn't inspire a lot of confidence.

Hey, if I want kookiness, I can always go back to USENET. At least there I don't have to wade through an ad-laden website. And I can use newsreader filters to screen out the loons

That said, I do surf in to Space.com's groups from time to time to read some of the posts; however, I don't feel any great urge to jump in.

P.S. The post above can apply equally to other discussion groups. For example, I could just as easily substitute http://www.habitablezone.com/ for Space.com

Posted by: dvandorn Mar 7 2006, 09:54 PM

Amen to that, brother. It's a testament to this place that I've never even had the urge to look and see if it's possible to filter someone out, here.

-the other Doug

Posted by: AlexBlackwell Mar 7 2006, 10:03 PM

I don't know. I did see "Ignore User" under "Profile Options." However, I'm not sure whether this applies only to personal messages or whether the user's posts will be filtered out as well.

Posted by: AlexBlackwell Mar 13 2006, 10:11 PM

Erica Hupp/ Merrilee Fellows
Headquarters, Washington
(202) 358-1237/ (818) 393-0754

William Jeffs
Johnson Space Center, Houston
(281) 483-5111

March 13, 2006

RELEASE: 06-091

NASA's Stardust Findings May Alter View of Comet Formation

Samples from comet Wild 2 have surprised scientists, indicating the
formation of at least some comets may have included materials ejected by
the early sun to the far reaches of the solar system.

Scientists have found minerals formed near the sun or other stars in the
samples returned to Earth by NASA's Stardust spacecraft in January. The
findings suggest materials from the center of the solar system could
have traveled to the outer reaches where comets formed. This may alter
the way scientists view the formation and composition of comets.

"The interesting thing is we are finding these high-temperature minerals
in materials from the coldest place in the solar system," said Donald
Brownlee, Stardust principal investigator from the University of
Washington, Seattle.

Scientists have long thought of comets as cold, billowing clouds of ice,
dust and gases formed on the edges of the solar system. But comets may
not be so simple or similar. They may prove to be diverse bodies with
complex histories. Comet Wild 2 seems to have had a more complex history
than thought.

"We have found very high-temperature minerals, which supports a
particular model where strong bipolar jets coming out of the early sun
propelled material formed near to the sun outward to the outer reaches
of the solar system," said Michael Zolensky, Stardust curator and
co-investigator at NASA's Johnson Space Center, Houston. "It seems that
comets are not composed entirely of volatile rich materials but rather
are a mixture of materials formed at all temperature ranges, at places
very near the early sun and at places very remote from it."

One mineral found in the material brought back by Stardust is olivine, a
primary component of the green sand found on some Hawaiian beaches. It
is among the most common minerals in the universe, but scientists were
surprised to find it in cometary dust.

Olivine is a compound of iron, magnesium and other elements. The
Stardust sample is primarily magnesium. Along with olivine, the dust
from Wild 2 contains high-temperature minerals rich in calcium, aluminum
and titanium.

Stardust passed within 149 miles of comet Wild 2 in January 2004,
trapping particles from the comet in an exposed gel. Its return capsule
parachuted to the Utah desert on Jan. 15. The science canister with the
Wild 2 sample arrived at Johnson on Jan. 17. Samples have been
distributed to approximately 150 scientists for study.

"The collection of cometary particles is greater than we ever expected,"
said Stardust Deputy Principal Investigator Peter Tsou of NASA's Jet
Propulsion Laboratory, Pasadena, Calif. "The collection includes about
two dozen large tracks visible to the unaided eye."

The grains are tiny, most smaller than a hair's width. Thousands of them
appear to be embedded in the glass-like aerogel. A single grain of 10
microns, only one-hundredth of a millimeter (.0004 inches), can be
sliced into hundreds of samples for scientists.

In addition to cometary particles, Stardust gathered interstellar dust
samples during its seven-year journey. The team at Johnson's curatorial
facility hopes to begin detailed scanning of the interstellar tray
within a month. They will initiate the Stardust at Home project. It will
enable volunteers from the public to help scientists locate particles.

After registering, Stardust at Home participants may download a virtual
microscope. The microscope will connect to a server and download "focus
movies." The movies are images of the Stardust Interstellar Dust
Collector from an automated microscope at the Cosmic Dust Lab at
Johnson. Participants will search each field for interstellar dust impacts.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Stardust
mission for NASA's Science Mission Directorate, Washington. Lockheed
Martin Space Systems, Denver, developed and operated the spacecraft.

Stardust science team members presented their first findings this week
at the annual Lunar and Planetary Science Conference in League City, Texas.

For more information about Stardust on the Web, visit:

http://www.nasa.gov/stardust

For information about NASA and agency programs on the Web, visit:

http://www.nasa.gov/home

- end -

Posted by: AlexBlackwell Mar 13 2006, 10:25 PM

Emily just http://www.planetary.org/blog/article/00000490/ a new entry on this in her blog.

Posted by: BruceMoomaw Mar 14 2006, 01:45 AM

I have to admit that I don't understand why the discovery of olivine is considered "surprising" -- they've been detecting it in IR spectra of coma dust for a long time.

Posted by: AlexBlackwell Mar 14 2006, 02:03 AM

True.

And the model where refractory materials could have been blown from the sun outwards to the comet-forming regions is also not new.

Posted by: nprev Mar 14 2006, 03:20 AM

Hmm. Perhaps the element of surprise here is that olivine grains survived in an inner-system comet without alteration by water? As you all certainly recall, the presence of abundant olivine on the surface of Mars has been touted as evidence that the planet has been dry for most of its history.

Maybe we don't understand something about the chemistry and "catalytic" (or circumstantial) interactions between H2O and olivine. For example, is a significant atmosphere of a given composition required for olivine to decompose as it does on Earth's surface, and therefore is this assumption altering our expectations?

Posted by: BruceMoomaw Mar 14 2006, 03:56 AM

It would be more accurate to say that low temperatures are already known to slow the reaction of olivine and water WAY down, even when you're talking about cold liquid water -- a fact which a growing number of abstracts are citing to suggest that the presence of olivine scattered across Mars isn't really all that strong as evidence of a frozen surface in the Noachian era (especially since it also now looks as though most of the olivine that's been detected there was thrown up volcanically onto the surface during the Hesperian era, AFTER Mars had lost its initial dense atmosphere and that atmosphere's greenhouse effect). The same thing, of course, applies to comets -- whose total fraction of their water supply that's ever been melted into liquid form, even briefly, is probably much smaller than Mars' percentage.

Posted by: dvandorn Mar 14 2006, 10:00 AM

In re this first press conference...

First, why no mention of the organic materials we've been hearing rumors about? A lot of discussion of minerals, but it took a reporter's question about organics for them to discuss it at all. And when they did, all they discussed was how difficult it is to differentiate between real organics in the samples and contamination from the lab. Are we to take it that we won't get *any* discussion of possible organics in the samples, because they're too gun-shy to ascribe organics to the samples themselves?

Second, these guys seem really blown away by seeing high-temperature-differentiated minerals (olivines, pyroxines, anorthosites, etc.) in a body that accreted in the outer solar system. Anyone ever mention the T-Tauri winds to these guys? It's been known for a long time that the Sun blew all of the loose material from the solar nebula out into a shell at *least* as far out as the Kuiper belt during its T-Tauri stage. So why does it surprise anyone that we find grains of high-temperature minerals in bodies that accreted in the Kuiper belt? After all, those bodies had to have vacuumed up a lot of the dust and gasses pushed out from the inner system during the T-Tauri epoch, right?

I guess it's just surprising to me how amazed these guys get when their results support decades-old theories...

On the plus side, I heard one of the panel members state that Stardust@Home ought to get going in the next couple of weeks. I'm looking forward to hearing from them.

-the other Doug

Posted by: edstrick Mar 14 2006, 10:44 AM

I think one reason they're giving a lot of attention to the high-temp crystals and stuff is that they're the "easy pickings"... large grains that penetrate well into the aerogel and make nice dots at the end of tracks. Unaltered outer solar system dust-bunny sub-sub-micrometer grain aggregates are gonna be a lot harder to get and process, even if it's most of the total sample returned. Only micrometer'ish sized solitary grain clusters of hydration rich or organics rich outer-nebula stuff is going to be unaltered.

Posted by: RGClark Mar 14 2006, 11:46 AM

The only theory offered for the formation of the high temperature olivine is that it formed close to the Sun or another star.
HOWEVER, the theory of radiogenic heating in comets early in the Solar Systems history could also explain this.
This theory is controversial ONLY because it would raise the possibility of life on comets. Note though that radiogenic heating is a leading theory for the origin of the heating in the icy, comet-like world of Enceladus (they both have water jets.)
Note as well the theory the olivine formed close to the Sun or a star would not explain why Kuiper belt object Quaoar apparently still has internal heating, whereas radiogenic heating WOULD explain it:

Chilly Quaoar had a warmer past
Mark Peplow
Crystalline ice suggests remote object has radioactive interior.
Published online: 8 December 2004.
http://www.nature.com/news/2004/041206/pf/041206-7_pf.html


Bob Clark

Posted by: BruceMoomaw Mar 14 2006, 12:00 PM

Bear in mind that they are only talking about such heat being adequate to create olivine in the very biggest KBOs -- comets would be MUCH too small for it. However, this is really separate from the possibility that smaller objects like comets did undergo SOME significant degree of Al-26 internal heating early on.

Posted by: edstrick Mar 14 2006, 12:40 PM

RG Clark: "....This theory is controversial ONLY because it would raise the possibility of life on comets. ..."

Bull.

It's controversial because there is no indication from interplanetary dust studies, founded by Brownlee, and comet studies, that small cometary bodies ever heated up enough to produce meltwater, much less silicate melt. Evidence continues to accumulate that comets are underdense bodies ice that never melted and dusts that never turned to "mud", unlike what we think are middle and outer belt asteroid materials like the serpentinized carbonaceous chondrites and things like the Tagash Lake meteorite.

This is not to say that giant KBO's didn't heat, differentiate, melt ice and even melt silicates briefly. They probably did. But a near-Pluto sized KBO is a vastly larger object with vastly more mass per unit surface area than a few km to few tens of km comet nucleus.

Comets are probably dominated by the smaller KB objects, with some small fraction being collisional fragments from larger ones, and some being objects from the outer belt or from near Jupiter's orbit, but they will be a small fraction of the total.

Note that the presumed parent body of the Kreutz sungrazer comet family, which has been suspected of originally being perhaps 100 km or more across, (I don't have the number at hand), broke up into totally fragile crumbly chunks that disintegrate in space with little provocation like other comets have done. That one probably never melted, at least the pieces of it we see. Maybe there's a core somewhere along the sungrazers' orbit we haven't seen in human history.

Posted by: RGClark Mar 14 2006, 02:11 PM

???

Clays have been found both in micrometeorites and carbonaceous chondrites:

CHARACTERISTICS OF PHYLLOSILICATES IN MICROMETEORITES DERIVED FROM SYNCHROTRON X-RAY DIFFRACTION ANALYSIS.
67th Annual Meteoritical Society Meeting (2004) 5074.pdf
http://www.lpi.usra.edu/meetings/metsoc2004/pdf/5074.pdf

STRUCTURE AND BONDING OF CARBON IN CLAYS FROM CI CARBONACEOUS CHONDRITES.
Laurence A.J. Garvie1 and Peter R. Buseck1,2, 1Department of Geological Sciences, Arizona State University,
Tempe, Arizona 85287-1404, ****@asu.edu, 2Department of Chemistry and Biochemistry, Arizona State
University, Tempe, Arizona, 85287
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1515.pdf

ASTEROIDAL WATER: THE EVIDENCE FROM THE AQUEOUS ALTERATION EXHIBITED BY CHONDRITIC METEORITES.
M.E. Zolensky, SN2, NASA Johnson Space Center, Houston, TX 77058 USA
Eleventh Annual V. M. Goldschmidt Conference (2001)
http://www.lpi.usra.edu/meetings/gold2001/pdf/3052.pdf

THE PETROLOGY OF FINE-GRAINED MICROMETEORITES: EVIDENCE FOR THE DIVERSITY OF PRIMITIVE ASTEROIDS.
M. J. Genge1, J. Bradley2, C. Engrand3, M. Gounelle1, R. P. Harvey4and M. M.Grady1, 1Department of Mineralogy, The Natural History Museum, London SW7 5BD,2MVA Inc, Atlanta, USA,3C. S. N. S. M., Orsay, France, 4Case Western Reserve Univ., Ohio, USA
Lunar and Planetary Science XXXII (2001)
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1546.pdf

Mineralogy of Phyllosilicate-rich Micrometeorites and Comparison with Tagish Lake CI and Sayama CM Chondrite.
Noguchi, T.; Nakamura, T.
32nd Annual Lunar and Planetary Science Conference, March 12-16, 2001, Houston, Texas, abstract no.1541
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1541.pdf

Phyllosilicate is another word for clay.

Note also that the theory of radiogenic heating in comets was proposed because such radioactive isotopes were *detected* in carbonaceous meteorites. From this it was deduced there would be enough early in the solar systems history to heat the interior of comets above the melting point of water.
The ONLY reason this theory remains controversial is because it would raise the possibility of life in comets.


Bob Clark

Posted by: The Messenger Mar 14 2006, 02:52 PM

This is a great debate!

I don't see how the sun could be the source of olivine - doesn't it decompose at much lower temperatures? I also wonder why it is that everything that bops into the inner solar system is always assumed to have the same primal origins as everything else. Isn't it reasonable to assume that since the sun is at least a second generation star, the composition of the solar mass could contain inhomogenious elements from more than one star and a with a variety of formation histories? For example, Phoebe appears to have a different history from any of the other Saturn moons - did it come from the asteroid belt, or interstellar space?

Posted by: AlexBlackwell Mar 14 2006, 05:20 PM

Emily has another http://www.planetary.org/blog/article/00000491/.

Posted by: AlexBlackwell Mar 14 2006, 06:16 PM

As Emily http://www.planetary.org/blog/article/00000491/, and which I never really doubted, the Stardust team is certainly aware of the X-wind model by Shu et al., notwithstanding their "surprise" at the refractories in the Stardust samples. Here are a few X-wind references (just bare URLs) off the top of my head:

http://www.sciencemag.org/cgi/reprint/271/5255/1545.pdf
http://www.space.com/scienceastronomy/solarsystem/chondrites_010305.html
http://www.lpi.usra.edu/meetings/ess2005/pdf/9024.pdf
http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1471.pdf

Posted by: AlexBlackwell Mar 14 2006, 06:33 PM

Coincidentally, the http://meteoritics.org/Current%20Issue.htm has a special section entitled "Experimental Studies in Preparation for the Analyses of Samples Collected by Stardust."

Posted by: The Messenger Mar 14 2006, 07:24 PM

Thanks Emily, This is great!

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.

Posted by: Gsnorgathon Mar 14 2006, 09:25 PM

You'll note from Emily's update:

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.

Posted by: AlexBlackwell Mar 14 2006, 10:11 PM

I guess that's why I think http://www.msnbc.msn.com/id/11744581 probably wouldn't work.

Posted by: The Messenger Mar 15 2006, 03:22 PM

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.

Posted by: centsworth_II Mar 15 2006, 04:35 PM

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

Posted by: AlexBlackwell Mar 15 2006, 07:16 PM

As Mark Peplow http://www.nature.com/nature/journal/v440/n7082/full/440260a.html 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."

Posted by: RGClark Mar 16 2006, 01:24 PM

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

Posted by: RGClark Mar 17 2006, 04:36 AM

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

Posted by: BruceMoomaw Mar 17 2006, 03:37 PM

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.)

Posted by: RGClark Mar 17 2006, 05:59 PM

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

Posted by: BruceMoomaw Mar 17 2006, 10:33 PM

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.

Posted by: RGClark Mar 17 2006, 10:44 PM

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


- Bob Clark

Posted by: nprev Mar 18 2006, 12:50 AM

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?

Posted by: ljk4-1 Mar 30 2006, 04:45 PM

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/

Posted by: ljk4-1 May 16 2006, 03:09 PM

http://stardust.jpl.nasa.gov/news/status/060512.html

Stardust Analysis Update

Dr. Donald Brownlee
Stardust Principal Investigator

May 12, 2006

[Group photo of Stardust science team at Timber Grove Inn
near San Francisco, California]

The Stardust Preliminary Examination Team (PET) is now in the second
half of the six month period to complete the initial characterization of
the returned comet samples. ....

(Editied. Hardly any point in posting the link if you're going to copy and paste the whole damn press release!)

Posted by: belleraphon1 Apr 6 2011, 04:13 PM

Frozen Comet Had a Watery Past

http://uanews.org/node/39041

"In our samples, we found minerals that formed in the presence of liquid water," Berger said. "At some point in its history, the comet must have harbored pockets of water."

"What we found makes us look at comets in a different way," Lauretta said. "We think they should be viewed as individual entities with their own unique geologic history."

That is if the minerals they found formed on the comet....

Pretty cool.

Craig

Posted by: Holder of the Two Leashes Aug 15 2014, 02:38 PM

A report out from JPL on the interstellar dust analysis:

http://www.jpl.nasa.gov/news/news.php?release=2014-278

Quote: "Seven rare, microscopic interstellar dust particles that date to the beginnings of the solar system are among the samples collected by scientists who have been studying the payload from NASA's Stardust spacecraft ..." [Emphasis added]

Apparently the JPL press office is so used to opening Stardust updates with the phrase "beginnings of the solar system" that they failed to notice that in this case interstellar dust has nothing to do with the solar system.

Note: Ooops. Didn't notice Explorer1 already posted this press release on another Stardust topic.

Posted by: Explorer1 Aug 15 2014, 04:33 PM

That's fine; analysis is more appropriate than the EPOXI thread. Maybe a mod can move mine?

Posted by: algorithm Aug 15 2014, 06:19 PM

I read the piece linked to and it included the following phrase.

'The particles would be the first confirmed samples of contemporary interstellar dust.'

I was unsure what 'contemporary, meant in this context.

Posted by: Phil Stooke Aug 15 2014, 06:21 PM

Contemporary = not in ocean sediments ?

Phil

Posted by: Holder of the Two Leashes Aug 20 2014, 04:31 AM

According to this report, the theory is these grains can't be more than 100 million years old:

http://newscenter.berkeley.edu/2014/08/14/seven-tiny-grains-captured-by-stardust-likely-visitors-from-interstellar-space/

Quote: "This dust is relatively new, since the lifetime of interstellar dust is only 50 to 100 million years, so we are sampling our contemporary galaxy," said Butterworth.

So I guess one way of looking at it is that Tyrannosaurus Rex is contemporary. Trilobites ... not so much so.