Posted: Tue Oct 16, 2007 4:45 pm Post subject: Re: Tempel 1 / Deep Impact Reply with quote
OP "mgmirkin"
http://gallery.spitzer.caltech.edu/Imag ... sc2005-18a
Hmm, interesting. Yes, good to find the "red-handed" admission:
Though the post-impact spectrum is still being analyzed, it shows that Tempel 1's ejecta contain the following chemicals: smectite clay; iron-containing compounds; carbonates, the minerals in seashells; crystallized silicates, such as the green olivine minerals found on beaches and in the gemstone peridot; and polycyclic aromatic hydrocarbons, which are carbon-containing compounds found in car exhaust and on burnt toast.
Astronomers were most surprised to see clay, carbonates, and crystallized silicates because these chemicals are thought have formed in warm environments, possibly near the Sun, but away from the chilly outer neighborhood of comets. How did these compounds get inside comets? One possibility is that materials in our early solar system mixed together before being sorted out into individual bodies.
Not a mention of water in the bunch! Not even a mention of the OH [
hydroxyl radical] that was later claimed to be "proof" of water ice on the nucleus (of course in far too small a quantity), despite Wal Thornhill's description of the process of OH production as part of the Electric Comet model.
Additional reading:
(Surprises Found in Comet Recipe )
http://www.space.com/scienceastronomy/0 ... _soup.html
Lisse's team found standard comet components, such as silicate. The astronomers likened the silicate grains to crushed gems, saying they were smaller than typical sand grains.
There were surprises, too, such as clay and carbonates -- the stuff of seashells. These were unexpected because they are thought to require liquid water to form.
"How did clay and carbonates form in frozen comets?" Lisse said in a NASA statement released today. "We don't know, but their presence may imply that the primordial solar system was thoroughly mixed together, allowing material formed near the Sun where water is liquid, and frozen material from out by Uranus and Neptune, to be included in the same body."
(Deep Insight: Comet Buster Reveals Dusty Secrets )
http://www.space.com/scienceastronomy/0 ... sight.html
Snowball's chance
Water is a key ingredient to comet theories. Scientists originally called comets "dirty snowballs," but recent evidence of a dearth of water has made snowy dirtballs seem more appropriate.
Measurements from the Submillimeter Wave Astronomy Satellite (SWAS) recorded only about 550 pounds of water per second from the comet surface. This emission was similar to what was seen by SWAS before the collision.
"It's pretty clear that this event did not produce a gusher," said Gary Melnick of the Harvard-Smithsonian Center for Astrophysics. "The more optimistic predictions for water output from the impact haven't materialized, at least not yet."
The interior of a comet is partly frozen, but water vapor and other gases evaporate off of a comet due to heat from the Sun. This emission is what gives some comets a tail.
A comet like Tempel 1, which has a short orbital period of 5.68 years, has been baked by the Sun many, many times. Its outer edge was expected to be dry down to three feet, but if little water is detected, this dry zone will need to be extended theoretically deeper.
Schultz, however, thinks it is premature to say what the water content is. He thinks the only thing that can be said for sure is that Tempel 1 is not an ice cube. Observers are waiting to see if more gases might get expelled from the comet's new crater.
For full coverage (of all the gory details) of Deep Impact, go here:
http://www.space.com/deepimpact/
And here:
http://solarsystem.nasa.gov/deepimpact/index.cfm
http://solarsystem.nasa.gov/deepimpact/ ... /index.cfm
For the uber-mainstream opinion, see Wikipedia:
http://en.wikipedia.org/wiki/Tempel_1
http://en.wikipedia.org/wiki/Deep_Impac ... 29#Results
Makes me want to gnash my teeth to the point of wearing them down to a fine white powder... Kind of like talc. *wink*
Of course, one could take the Deep Impact data on the "rocky" nature of the "comet" and compares it to the data from Stardust, which happens to be in rough agreement:
(NASA's Stardust Comet Samples Contain Minerals Born in Fire )
http://www.space.com/scienceastronomy/0 ... pdate.html
Researchers studying samples of Comet Wild 2 (pronounced "Vilt 2") embedded in Stardust's gel-filled collector found that the minerals formed under extremely high temperatures - such as those near a star - and not in the frigid cold expected at the Solar System's edge, where most short-term comets originate.
"In the coldest part of the solar system we've found samples that formed at extremely high temperatures," said Donald Brownlee, Stardust's principal investigator at the University of Washington in Seattle, during a Monday press conference. "When these minerals formed they were either red hot or white hot grains, and yet they were collected in a comet, the Siberia of the Solar System."
The finding - announced on the 20th anniversary of the European probe Giotto's rendezvous with Comet Halley in 1986 - perplexed Stardust researchers and added a new wrinkle in astronomers' understanding of how comets, and possibly the Solar System, formed.
[...]
Astronomers aren't sure whether the minerals found in Stardust's comet samples formed near the Sun or around another star, though isotope scans are expected determine that for sure in upcoming tests, Brownlee said. Olivine, a mix of iron and magnesium that appears green on some Earth beaches, is one of the several surprising compounds found in the Wild 2 samples, he added.
[...]
But if Stardust's comet samples are found to be local to the Solar System, and not from some distant start, they'd suggest a sort of transportation system to fling particles formed near the Sun out past the orbit of Pluto and into the comet realm, researchers said.
"If this mixing is occurring, as suggested by these results, than how do you preserve any kind of zoning in the solar system," Zolenksy said. "It raises more mysteries."
(Stardust Findings Suggest Comets More Complex than Thought)
http://www.nasa.gov/mission_pages/stard ... t_jsc.html
Comets may be more than just simple conglomerations of ice, dust and gases.
[...]
Scientists have found a wide range of compositions and structures for the comet Wild 2 particles that were captured and returned to Earth by the Stardust mission. Their findings indicate the formation of at least some comets may have included materials ejected from the inner solar system to the far and cold outer edge of the solar nebula.
[...]
Minerals formed near the sun or other stars were in the samples returned to Earth by NASA's Stardust spacecraft in January. The findings suggest materials from the inner regions 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.
"We have found very high-temperature minerals, which supports a particular model where strong bipolar gas 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, NASA cosmic mineralogist and Stardust co-investigator at the 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."
[...]
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 certainly is made up of components of more complex history than thought.
Scientists found a wide variety in particle composition and size in the Wild 2 samples. Most of the Wild 2 samples appear to be weakly constructed mixtures of very small grains with a few larger grains. Also, a wide range of high- and low-temperature minerals, from olivine to low- and high-calcium pyroxene compositions, is present in the Wild 2 samples.
Such a diversity of high- and low-temperature minerals requires a wide range of formation conditions, probably reflecting different formation locations. Many particles did not form in the cold environment and location(s) where cometary ices condensed.
They needed high temperatures to form as well as complex and as yet little understood dynamical processes to end up where comets actually formed. Also, particles from different environments must have undergone some process of accretion to end up as aggregates composed of different minerals.
[...]
In addition to finding these varied compositions in the Wild 2 samples, Stardust investigators found a wide diversity of particle densities. The captured Wild 2 samples are predominantly fine-grained, loosely bound aggregates, most also containing much larger individual crystals of olivine, pyroxene and iron/nickel sulfides. All analyses suggest that small and large Wild 2 particles are composed of a similar, if not identical, suite of minerals.
"Many researchers, but not all, have thought that cometary solids are similar to interstellar dust, which is generally fine grained," said Friedrich Horz, NASA planetary scientist at JSC and lead author of a paper on impact features on Stardust and comet Wild 2 dust. "These models entail that such particles existed during the formation of comets, as 'leftovers' from the initial gas and solid mixture that were not processed further during comet formation in the cold environment from the sun."
Scientists found a much wider diversity of particle densities, including dense minerals, than advocated earlier by some researchers.
"We see and demonstrate for the first time that there is a continuum between fine particles and more dense objects, the latter including pure minerals of, for example, olivine and iron sulfide," said Horz. "The range in density and cohesion that we saw and infer thus disagrees specifically with the popular model that comets are composed of only fine grains. A minority, however, did allow for particles of variable density. We have confirmed the latter viewpoint."
Stardust's pre-mission predictions included a wide range of sizes. Thus the findings substantiate the view of highly variable particle sizes. The specific size distribution found in Wild 2 samples differs from that of comet Halley dust (Stardust has fewer fine-grained particles) and from that of comet Grigg-Skjellerup (Stardust is more fine-grained).
(Icy comet held hot minerals: scientists)
http://www.abc.net.au/news/stories/2006 ... 591718.htm
Particles from any icy comet that were collected and returned to Earth aboard a NASA science satellite show dozens of minerals that form only in extreme heat.
This finding complicates theories about how the solar system formed.
Prevailing theories about the solar system's formation cannot explain how this high temperature material ended up in the frigid regions beyond Neptune's orbit, the so-called Kuiper Belt where comets formed.
"Remarkably enough, we have found fire and ice," University of Washington spokesman and Stardust principal investigator Professor Donald Brownlee said.
"We've found samples from the coldest part of the solar system that have mineral grains formed under extremely high temperatures."
The grains include an exotic titanium-vanadium-nitrogen blend that forms in temperatures higher than 1,100 degrees Celsius.
The discovery leads scientists to two possible conclusions - either the minerals formed in the hottest, inner-most region of the nebula that eventually became our solar system or they came from another star.
"If it was formed in our solar system, then it had to be transported from the hottest regions to the coolest," Professor Brownlee said.
Scientists estimate the minerals would have had to be closer to the sun than Mercury to form and they would have had to be flung more than 45 times the distance of Earth to the sun to reach the Kuiper Belt region where the comets were born.
(Icy comet yields hot minerals)
http://www.abc.net.au/science/news/spac ... 591934.htm
Scientists studying comet samples returned by the Stardust spacecraft have uncovered a cosmic conundrum. How did minerals that form in extremely hot temperatures end up inside an icy comet?
"When they formed, they were either red-hot or white-hot and we found them in the Siberia of the solar system," says Stardust lead scientist Professor Donald Brownlee, with the University of Washington.
[...]
The comet formed in the frigid Kuiper Belt region located beyond Neptune's orbit and was a relatively new traveller to the inner solar system when it encountered the NASA probe.
[...]
The discovery of exotic, high-temperature minerals rich in calcium, aluminum and titanium complicate generally accepted theories about how comets form.
Far from simple icy bodies with clouds of gas and dust, comets, or at least Comet Wild 2, now appear to be a blend of materials formed at all temperature ranges.
Forging metals
Brownlee and other Stardust researchers expect to learn whether the high-temperature metals were forged near the center of the nebular cloud that eventually became our solar system or whether they come from another star.
"If it was formed in our solar system, then it had to be transported from the hottest regions to the coolest," says Brownlee.
The samples also show a rich supply of olivine, an iron-magnesium blend of minerals, which on Earth can be found in peridot gemstones and in the green sand on some Hawaiian beaches.
Though it is one of the most common minerals in the universe, scientists did not expect to find it in a comet.
Olivine forms in temperatures of about 1100°C, which means the mineral would have had to form closer to the Sun than Mercury and then somehow be flung out more than 45 times the distance of the Sun to Earth.
For the uber-mainstream opinion, go to Wikipedia:
http://en.wikipedia.org/wiki/Stardust_%28spacecraft%29
For more on Stardust:
http://www.nasa.gov/mission_pages/stard ... index.html
http://stardust.jpl.nasa.gov/home/index.html
One might also be inclined to comment that not only Tempel 1 (Deep Impact mission) or Wild 2 (Stardust mission) refuted the standard comet model. Comet Linear also already provided refutation of the dirty snowball and/or the icy comet model:
(A Comet's Life: Icy Adventure From Birth to Death; Comet LINEAR.)
http://www.space.com/scienceastronomy/s ... 517-5.html
Weaver, Mumma and others say the comet, popularly called LINEAR, might just be an oddball. But their suspicion is that it represents a whole newly realized class of comets that formed in abundance back when the solar system was developing, but were then swallowed by the Sun, slammed into Earth or lost to interstellar space.
In this scenario, LINEAR represents a rare survivor.
And its rarity makes its observation all the more fortuitous. Other comets have been studied as they swing around the Sun, which burns off their surface and creates a halo of gas and dust whose composition scientists can measure. But never has a comet performed a death dance in front of so many telescopes.
Hermann Boehnhardt, a European Southern Observatory researcher who was not involved in the studies, said they collectively represent a glimpse into pristine material, uncontaminated since the solar system formed, and are the first real measurements that can be used to test models of solar system formation.
"It is a step forward," Boehnhardt said, "and an important step."
[...]
Weaver's international team used the Hubble Space Telescope and the Very Large Telescope to spot at least 16 chunks roughly 110 yards (100 meters) across.
Weaver thinks these pieces represent "primordial building blocks" that became a comet as the result of "a continual buildup of bodies of increasing size via mutual collisions and sticking."
In one of the other studies, the gases emitted by LINEAR were found to be nearly identical before and after the breakup, indicating that the entire comet, inside and out, was formed at roughly the same distance away from the Sun. This means the comet evolved to maturity before it was tossed out to the Oort Cloud, a distant reservoir of comets.
Like LINEAR, other comets in the Oort Cloud are sometimes drawn into the inner solar system after billions of years. Others that have been studied in detail were all found to be related in how they were composed.
"But Comet LINEAR is an exception," said Mumma, the NASA researcher.
Mumma and his colleagues found four organic compounds, including carbon monoxide and methanol, to be scarce in LINEAR. The lack of these compounds indicates that the comet formed in a warmer region of the solar nebula.
[...]
Snowy Dirtball, Through and Through
In 1950, astronomer Fred Whipple gave the world a popular description of comets that has endured for five decades. He called them dirty snowballs. It was a simple way to think of a primordial ball of frozen gas and dust, and it also had the presumed benefit of being accurate.
But scientists had never actually seen the inside of a comet, and now Comet LINEAR has soiled the popular definition slightly.
Before LINEAR's breakup, the SOHO spacecraft, which normally monitors the Sun, had been keeping an eye on the comet. A French-Finnish instrument called SWAN was measuring water in the comet's halo.
Then came the comet's swan song and the instrument found that the density of water in the inner chunks was between 15 and 30 kilograms (33 and 66 pounds) per cubic meter, far less than the figure of 500 often assumed for comets.
In comparing this with the comet's total mass before the breakup, researchers figure that the amount of ice was about 100 times smaller than the total mass.
"Comet Linear was more like a snowy dirtball than a dirty snowball," Weaver said.
[...]
Weaver, the Johns Hopkins researcher, described the comet as being somewhat like a collection of multi-sized marbles, each covered in ice, all stuffed in a bag. Such rubble piles have been found to be the basis for asteroids, including Eros. But while it is also a popular theory for describing comets, there had been only indirect supporting evidence.
Now the evidence is clear. And Weaver suspects that the building blocks of Comet LINEAR would have been structurally weak.
As the outer surface of the comet burned off on its approach to the Sun, these building blocks were exposed and peeled off, one by one. And because the comet contained far less ice than researchers expected, it lacked the glue that might hold other comets together.
"It is believed that ices hold the [building blocks] together, so a lack of ices could have been a contributing factor in why the comet broke up," said Farnham, the University of Texas researcher whose group examined the asteroid's rotation and the mass of its many remains.
In the SOHO study of the LINEAR's water, researchers ruled out melting as the sole reason for breakup. Instead, they agree that the delicate assembly of the comet's original building blocks is to blame.
[...]
A handful of other scenarios have been devised to account for why comets break apart, including a frenetic rotation rate or the gravity of planet or other massive object.
But LINEAR was nowhere near a massive planet.
And Farnham's team used ground-based telescopes to study how LINEAR moved about its axis as it sped through space. They determined that the comet rotated at least once every 12 hours, not rapid enough to have been responsible for the breakup.
But there is other evidence, not yet published, indicating that the rotation rate may be as fast as 2.5 hours. If correct, then rotation might have played a partial role in the breakup, Weaver said.
Imre Toth, a Hungarian researcher and co-author with Weaver, suggested in another recently published paper that the comet might have collided with other space debris in late 1999 or early 2000, disrupting the nucleus. This would mean that the pieces observed after the breakup were not primordial building blocks.
Weaver called Toth's hypothesis interesting but improbable.
[...]
"I envision the nucleus as a pile of large cotton balls," Mumma said. "Each ball is hard to pull apart because of interlocking fibers, but the pile itself is very weakly bound and so is easily dissembled."
[...]
Still, Comet LINEAR has not revealed all. Scientists remain puzzled over some apparently missing mass.
The mass of the large fragments studied by Weaver and his colleagues was to be about 100 times smaller than the estimated mass of the original nucleus in another study. Estimates of ice in the nucleus prior to its undoing, along with estimates of material in the tail, fall well short of solving this "missing mass" problem, Weaver said.
Farnham's team suspects that most of the comet's original mass is now hidden in pieces ranging from the size of a building to grains of sand. These bits would be too small to seen by telescopes.
(Comet Cracks Under Pressure After Rapid Brightening)
http://www.space.com/scienceastronomy/s ... 10503.html
What was at first a mundane comet zooming into the inner solar system suddenly brightened unexpectedly this spring and was on the verge of putting on a minor show by becoming visible to the naked eye.
Then it cracked under the pressure.
[...]
And though researchers aren't sure why a comet breaks up, {
They assume} it has to do with the way they blow off steam. As a comet heats up, its ice "sublimates" directly into gas, bypassing the liquid stage. This generates outward pressure.
"Kind of like a geyser like Old Faithful," Hergenrother explained, "the pressure builds up and finally [a piece] pops off."
[...]
Hergenrother and his colleagues have been watching this newly found comet for months using a University of Arizona telescope. It was a typical, rather mundane target that was not expected to brighten much.
"Then one day, all of a sudden -- whammo -- the thing got a hundred times brighter."
The jump in visual brightness occurred March 25-26, when it rose from an indistinct magnitude 12 to 10.7. A few days later, it was near magnitude 8. Then it
faded slightly, but began brightening again over the past two weeks and ultimately approached magnitude 6. {
Before it became over-stressed and broke up.}
{comments in
red}
And in the last article above, the mainstream still claims that sublimation / volatiles probably did it! Talk about having their collective heads in the sand (Hmm, silicates! Iron-rich? A little clay mixed in? Must be ice and volatiles! Watch out, it might start sublimating ant time now... Rolling Eyes ANY day now. *Taps his foot impatiently*)!
So, we've gone from comets as sublimating hunks of ice to comets as hunks of ice with a little dust to comets as hunks of dust with a little ice, to basically a giant rock in space with little or no water actually detected, which may still violently break up (despite lacking volatiles or materials to sublimate). Yet astronomers cling to the wet/icy comet model with irrational tenacity!
How many more refutations of the icy comet, the dirty snowball, or the snowy dirtball model must there be before it is abandoned entirely and the more appropriate [rocky, dusty] Electric Comet model is adopted?
I might also point out that there is a group of objects that may eventually settle the dispute and provide the link between asteroids and comets. That group is the Centaurs:
http://en.wikipedia.org/wiki/Centaur_%28planetoid%29
The centaurs are a class of icy planetoids
[...]
Three centaurs, Chiron, 60558 Echeclus, and 166P/NEAT 2001 T4, have been found to display cometary comas. Chiron and 60558 Echeclus are now classified as both asteroids and comets. It is possible that other centaurs may also be comets, but as of March 2006 no cometary behavior has been discovered for any others.
Cheers,
~Michael Gmirkin
Last edited by mgmirkin on Tue Oct 16, 2007 11:19 pm; edited 12 times in total
Still fighting off the technicolor yawn... 