Study: Samples of comet dust show a mix (NASA's Stardust mission

SAN FRANCISCO - Detailed observations from the first comet samples returned to Earth are debunking some of science's long-held beliefs on how the icy, celestial bodies form.

Scientists expected the minute grains retrieved from a comet Wild 2 to be made up mostly of interstellar dust — tiny particles that flow through the solar system thought to be from ancient stars that exploded and died.

Instead, they found an unusual mix of primordial material as if the solar system had turned itself inside out. Hot particles from the inner solar system migrated out to the cold, outer fringes beyond Pluto where they intermingled and congealed to form a comet.

"People imagine that comets form in total isolation, which is definitely not true," said Don Brownlee, a University of Washington astronomer who is the principal scientist for the $212 million Stardust mission.

Brownlee estimated that up to 10 percent of materials in comets may come from the inner solar system.

A series of papers detailing the first scientific results from the Stardust mission were to be published Friday in the journal Science and presented at an American Geophysical Union meeting Thursday.

A capsule carrying thousands of minuscule samples from comet Wild 2 returned to Earth last January after looping around the sun to capture the interstellar and comet debris and swooping past Wild 2 to scoop up dust.

Scientists had dubbed Wild 2 a frozen time capsule because it contained material preserved from the aftermath of the solar system's birth more than 4.5 billion years ago.

How material from the inner solar system could have ended up in comets is still a mystery. Brownlee said the solar system-forming process was probably chaotic and unstable, allowing high-temperature particles to loft billions of miles out to the edge of the solar system.

Many of the grains contained high-temperature minerals that likely formed in the hottest part of the solar nebula. At least one grain was made of a rare mineral seen in some meteorites, which are among the oldest samples in the solar system.

An analysis also found Wild 2 appeared to differ from comet Tempel 1, which was studied in NASA's Deep Impact mission. Last July, the space agency crashed a probe into Tempel 1 and studied the dust and ice spewing from its belly. It did not retrieve any samples from the surface.

In an accompanying editorial, Michael A'Hearn of the University of Maryland, who is also the Deep Impact chief scientist, said the Stardust results have gotten scientists thinking about their original views.

When dust particles from Comet Wild 2 struck a sponge-like "aerogel" collector in the Stardust
spacecraft, they left carrot-shaped imprints about a centimeter long. Credit: NASA

Dec 07, 2006
Stardust Shatters Comet Theory (2)
Mythic "Oort Cloud" Finds No Support in Comet Dust
(This TPOD originally ran on March 20, 2006)
It's now official. Minerals found in Comet Wild 2 dust particles can form only at high temperatures, and they cannot be distinguished from minerals found in meteorites and on rocky planets.
Dust particles ejected by Comet Wild 2 have provoked another surprise, contradicting the underlying assumptions of popular comet theory. When the Stardust mission returned "pristine comet material" from Comet Wild 2, project scientists were astonished to discover minerals that can only form at high temperatures - up to thousands of degrees Fahrenheit. And the dust particles reveal no indications of the water that cometologists expected.
Standard theory states that comets formed billions of years ago in an imagined icy "Oort cloud" at the very fringe of the Sun's domain, far beyond the orbit of Pluto. But the new findings require a quite different history. A NASA news release on March 13, 2006 summarized the problem with this understatement:
"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".
The disturbing discovery provoked a burst of creative attempts to rescue ideas stated as fact for at least thirty years. Michael Zolensky, Stardust curator and co-investigator at NASA's Johnson Space Center, Houston, suggested a novel interpretation that quickly caught on. "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 science writer interpreted Zolensky's comment this way: "The findings suggest materials from the center of the solar system could have traveled to the outer reaches where comets formed".
So an obsolete theoretical conjecture persists in human imagination, despite an undeniable fact: Nothing discovered about comets "over many years of profound discovery" points to an origin in the remote region assumed. A rational response will not exclude the question shouted by the new data. Could something be wrong with earlier suppositions about the region of comet formation - suppositions that never produced a successful prediction in the course of the space age?
As for the water (ice), that was supposed to be the primary constituent of comets. But the anticipated markers of water on the nucleus of Wild 2 are absent. One mineral present in the comet particles is olivine, an iron-magnesium silicate. In the presence of water and even modest heat, olivine will be converted to another mineral, serpentine. Place olivine in the presence of water (steam?) at the temperatures indicated for its formation, and it would be almost instantly converted to serpentine.
According to Stardust principal investigator Donald Brownlee, "no evidence of water has been detected in the particles". One sign of water, for example, would be the presence of hydrate silicates, Brownlee said, "but so far none of these have been found in the Stardust samples".
How, then, are we to reconcile the absence of water signatures in the comet dust with the fact that cometary comas often exude an abundance of water (or at least the hydroxyl radical OH). We answered that question in a three-part series, "Deep Impact - Where's the Water?" (first article here) The OH and whatever actual water may have been present in the coma were manufactured in the coma - an acknowledged "chemical factory". The vehicle for this process has already been observed - reactions between the oxygen ions in the coma plasma and the hydrogen ions in the solar wind. Charge exchange is now known to occur.
The least we can say today is that most comets contain no appreciable levels of water (i.e., most comets are neither "dirty snowballs" nor "icy dirtballs"), Additionally, it needs to be emphasized that there is no conflict between Stardust and Deep Impact data. Brownlee, who is not prone to overstate theoretical implications, points out that Stardust collected dust that was released directly from the surface in jets. "We're confident that the things coming out [of Comet Wild 2] are the same as those that went in", he told Space.com.
That means the material has not been processed by the chemical factory of the coma. "We believe that we collected the most pristine samples of a comet", he said. Hence, the failure to find a signature of water in the comet dust is consistent with all of the facts we have presented in previous discussion.
It is not unreasonable to suggest, therefore, that only one comet model can make sense of what is otherwise a hopelessly confused picture. This model is electric. And thanks to the technological successes of the space age, all of the markers reasonably expected of an electric comet have been found .
Of course the implications of the electric model do not end with the origin and dynamics of comets. They extend to virtually all of the theoretical sciences, and range from questions of electricity in remote space, to the nature of stars and the violent history of the solar system.
Additionally, as we intend to make clear, human memories of cometary and planetary catastrophe cannot be excluded from this investigation.

Far-out findings - new analysis suggests planets were formed from a giant mix
Imperial College
Department of Earth Science and Engineering
Thursday 14 December 2006
Particularly significant was the discovery of calcium aluminium inclusions, which are amongst the oldest solids in the Solar System and are thought to have formed close to the young Sun. This discovery suggests that components of the comet came from all over the early Solar System, with some dust having formed close to the Sun and other material coming from the asteroid belt between Mars and Jupiter. Since Wild-2 originally formed in the outer Solar System, this means that some of its composite material has travelled great distances.

didn't check the links, probably some are goners:

Did Jupiter Bully Other Planets in Sibling Rivalry?
by Robert Roy Britt
8 December 1999
One possible explanation, discussed in Thursday's issue of the journal Nature, is that Uranus and Neptune formed much closer to the center of the action than their current positions might indicate. In this scheme, Jupiter and Saturn were bullies of a protoplanetary playground, shoving the other two future giants out of the way.
Jupiter's Composition Throws Planet-formation Theories into Disarray
by Robert Roy Britt
Nov 17 1999
Examining four-year-old data, researchers have found significantly elevated levels of argon, krypton and xenon in Jupiter's atmosphere that may force a rethinking of theories about how the planet, and possibly the entire solar system, formed. Prevailing theories of planetary formation hold that the sun gathered itself together in the center of a pancake-shaped disk of gas and dust, then the planets begin to take shape by cleaning up the leftovers. In Jupiter's current orbit, 5 astronomical units from the sun, temperatures are too warm for the planetesimals to have trapped the noble gases. Only in the Kuiper belt -- a frigid region of the solar system more than 40 AU from the sun -- could planetesimals have trapped argon, krypton and xenon.

While lead researcher Tobias Owen does not put much stock in the idea that Jupiter might have migrated inward to its present position, other scientists on the team say the idea merits consideration. Owen expects the probes will find similarly high levels of noble gases in Saturn, Uranus and Neptune. Hints of these gases have even been found in the thick atmosphere of Venus, another planet now begging more study.
Jupiter gave birth to Uranus and Neptune
by Dr David Whitehouse
8 December 1999
Not too long ago, scientists regarded the orbits that the planets circle our Sun as being the ones they were born in. Now they are realising that this is not the case. Uranus and Neptune may have migrated outwards and Jupiter may have come in from the outer cold. Scientists have always been slightly puzzled by the positions of Uranus and Neptune because in their present locations it would have taken longer than the age of the Solar System for them to form. Scientists from Queen's University suggest that the four giant planets started out as rocky cores in the Jupiter-Saturn region, and that the cores of Uranus and Neptune were tossed out by Jupiter's and Saturn's gravity.
Newfound Moons Tell Secrets of Solar System
by Henry Fountain
August 12, 2003
The fact that most of the satellites' orbits are retrograde and eccentric speaks volumes about their origins: They had to have come from elsewhere, and been captured by the planets at some point. If they formed at the same time as the planets, from the spinning nebular disk, their orbits would be nearly circular and in the same direction as the planets' rotation, like the "regular" moons... In the case of the irregular satellites, they could not have shifted from an orbit around the Sun to an orbit around one of the giant planets without slowing down -- through friction in an atmosphere, perhaps; the influence of gravity; or a collision with another object... But there are two other possibilities for capture, Dr. Nesvorny said. One is that rapid growth of the core led to a corresponding increase in gravity, enough to pull down a nearby object. The other is that captured objects were a result of a collision between two planetesimals, the force of the collision being enough to dissipate the energy of at least one of them. Either of these two theories may be a more likely explanation for the satellites of Uranus and Neptune, which formed differently from Jupiter and Saturn, without the large amounts of gas.

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