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Recovering the Lost World --Jno Cook
Notes on Comet Temple 1.


[Table of Contents]

$Revision: 16.6 $
Contents of this file: [A Preliminary Note] [Deep Impact] [Predictions] [The Fireworks] [The Aftershocks] [Summing up] [Two Weeks Later] [Two Months Later] [Six Months Later] [Two Years Later] [Water Flowing Underground]

A Preliminary Note

NASA/JPL NEWS RELEASE Posted April 7, 2002

Deep Space 1 finds Comet Borrelly has hot, dry surface

"The spectrum suggests that the surface is hot and dry. It is surprising that we saw no traces of water ice," said Dr. Laurence Soderblom of the U.S. Geological Survey.

"We know the ice is there," he said. "It's just well hidden."

Deep Impact

For readers unfamiliar with the contact between the space probe "Deep Impact" and the comet "Temple-1" which happened on July 4, 2005, here is a replay.

The idea was to hit a comet with something massive, to see if comets really were "snowballs" -- as was suggested 60 years ago by Fred Wipple who coined the phrase "dirty snowball." The comets have been held to be distinct from asteroids and meteors (they are not), because there was no accounting for all the water on Earth without some extraterrestrial delivery system. After all, other planets and moons have no water or very little water. Earth has a lot. Only comets, on their wild orbits, could actually reach Earth.

Additionally, it was assumed that the enormous tails of coments must be ice subliming to water vapor due to the heating of the Sun (the sunward side of a comet may reach a temperature of a over a hundred degrees Fahrenheit). This theory reached conviction when hydroxyl (OH) molecules were identified in the tails of comets, and remained in vogue even after it was recognized that the Solar wind which shaped the glowing coma and tails of comets -- the long stretched-out streamers -- produced them by combining solar wind protons (H+) with cometary Oxygen (O-) ions released from silicates.

Comets were also held to be "dirty," that is, covered by dust, because a comet consisting of ice or snow would reflect sunlight, and the icy material would never 'sublimate' to form the million mile long tails.

All of this consists of a picture drawn by an eight year-old. The comets become bottle rockets leaving smoke trails in space -- at times 100 million miles long (the largest objects in the Solar System), coming from an icy object less than a few miles across. At times there are dual tails, spikes pointing toward the Sun, tails moving away at right angles to the main body, and curved horns at the front. But most of these other displays have been neglected. How can a comet a few miles across form a coma as large as the diameter of the Sun -- 864,000 miles -- and a tail longer than the distance from the Sun to Earth ?

There is obviously something wrong with this picture. What is even more wrong is the conviction that comets represent a coagulation of the dust of the primordial Solar System, and represent the formation of a planet from space dust which had gone wrong.

Never mind all the contrary data, the space probe "Deep Impact" was going to close in on the comet "Temple-1" and fire a 800 pound copper projectile at some 35,000 miles per hour and record the sequence of events both from a camera mounted on the projectile and from the space craft "Deep Impact" passing by at a safe distance of some 800 km. It was fully expected that the projectile would penetrate the comet, or would start a new 'sublimation' point which would gush water vapor into space for the next 1000 years.

Neither happened. In fact, nothing happened to any expectations, and the community of researchers were left scrambling for new theories.

Only a few people made correct predictions. There were based on very simple concepts: (1) a comet is a rock, and (2) the interactions will be electrical.

[Image: Comet Temple 1 moments after impact]
Image: Comet Temple 1 moments after impact by the probe from the space craft Deep Impact, July 4th, 2005.

Predictions

My Predictions

I made similar predictions, early on July 4th, 2005. I had predicted that at best only a small crater would be made (NASA expects a crater the size of a football stadium, over 150 feet deep and 250 feet in diameter). I also predicted that most likely the disturbance of the comet's electrical field by the approaching probe would cause an inrush of electrons speeding ahead of the arrival of the probe, causing an explosive arc at the impact location well before the probe arrived. This would most likely be followed by a sudden lightning stroke from the comet to the probe, ending in a brilliant green flare as 800 pounds of copper are vaporized. Nothing quite as spectacular as that happened.

[I should also point out that a flare traveling from an object in space had happened before. I recall an incident where a space craft, on approaching a moon (a planetary satellite), records what looks like a missile traveling at high speed from the moon. The space ship lost radio contact a second later. I need to source this.]

"Let me hedge my bets:" [I wrote] "If the probe makes contact with the comet, that is, if it makes a splashdown, it will provide a large blotch of copper to act as future site of any of the sporadic bursts of plasma that the comet now undergoes periodically."

Wrong again, sort of. What actually happened went completely beyond all expectation.

"It is also possible that no significant fireworks display will be seen. Comet Temple 1 comes to perihelion outside of the orbit of Earth, and originates from a space only beyond Jupiter. Its charge is likely to be mostly equalized to the local electrical field of the Sun, as can be seen from the jets of plasma which are only sporadically emitted."

"But I can certainly predict expected mainstream reactions."

  • "In the event of a small impact crater, NASA will come up with a new theory of super-hard ices in space, or suggest a 10 foot deep impenetrable crust of solidified rock."

  • "If the copper coated impact area becomes the favored location of new flares, it will prove to NASA that the comet is 'outgassing' at a new location, and probably due to an assumed deep hole made into the ice."

  • "A flareup of the comet before impact will suggest a slight mishap, to be cast in terms of, "An unexpected disruption of subsurface ice exploded in the direction of the probe, due to gravitational shock waves, gravitational eddy currents, gravitational inequalities, gravitational tidal forces." [joke]
    [Added note: This was a joke, but two months later NASA is suggesting that perhaps the other marks on the comet, which are normally assigned to impacts, might be due to underground "icy volcanic eruptions."]

    "We will again be left with nothing proven. Stay tuned." [That turned out to be correct.]

    Wallace Thornhill

    On July 3rd the Saturnian Group made some public predictions for the impact of the 800 pound projectile fired at Comet Temple 1. See the MOTD by Wallace Thornhill at [http://thunderbolts.info] (rewritten by them 4 Mar 2006).

    Specifics were listed as follows (abbreviated by me, with some comments added in square brackets)...

    Tom Van Flandern

    Long after the date of the impact I became aware of Tom Van Flandern's predictions, written in January of 2005, seven months before the impact date...

    "The comet nucleus is a single, solid asteroid. The impact will leave a small, shallow crater perhaps 10-20 meters in diameter, will produce no new jet, and will have no lasting consequences on the comet. It will simply produce an impact flash as the probe vaporizes, then will cause the comet's coma to temporarily brighten as new carbonaceous dust is ejected from the asteroid regolith and the impact crater."

    -- T. v Flandern, http://meteresearch.org

    Van Flandern's predictions were correct, based on the conviction that comets are rocks. Flandern does not allow for electrical interactions -- which ended up widening the "impact crater" and heaved into space an incredible amount of material.

    But it seems almost immaterial to be so dead-on correct, as Thornhill was, for there is a much larger issue -- the investment in the current model of comets as soft conglomerations of particulate matter. As Flandern writes, "The dirty snowball model is not sure what will happen, but has an explanation ready for each possibility. In that way, the model will not be placed at risk of falsification." He continues...

    "In brief, there is a general expectation that the impact will be gravity-dominated, while respecting the possibility that it might be strength-dominated. Either result will be argued as supporting the dirty snowball model for comets, even though the latter implies that the comet has been heavily processed and is not primordial. Just as Kuhn predicts for the nature of paradigm shifts, [T.S. Kuhn, "The Structure of Scientific Revolutions" (1996)] one model will not overthrow the other on merit, but the incumbent model will be patched until it so closely resembles the competitor that no important distinction remains. That helps to maintain the illusion that the progress of science is always forward."

    The Fireworks

    [July 5, 2005:] The first observations of July 4th, from a number of sources, compared with predictions as listed above.

    "... at best only a small crater would be made."

    Although difficult to measure at this time, NASA spokesperson suggest "at least bigger than a house," that is, 30 feet in diameter -- not 250 feet. This changed soon, for as soon as the impact crater was made, electrical arcing started up at the edges. Over the next few days this would enlarge the original crater to form a shallow depression as the electrical arcing wore away material from the sharp edge. Thus the original suggestion of a crater the size of a house was soon modified to suggest that it was much larger.

    "an explosive arc at the impact location well before the probe arrives ... followed by a sudden arc from the comet to the probe"

    The initial flare at the impact point was bright and small -- and of only 50 milliseconds duration -- and separate from a secondary conical blast of material. I have no idea of the timing of this bright spot, that is, when it first appeared. The probe was to take images every 2 seconds until impact, but the last image was transmitted 3.7 seconds before (calculated) impact. I would suggest it was 'hit' at this time. The probe was traveling a little over 6 miles per second, with 24 miles to go before impact. The probe also faltered twice in earlier transmissions during approach. It would suggest electrical disturbances, that is, plasma sheath shielding (mentioned as likely by Thornhill).

    ".. ending in a brilliant green flare as 800 pounds of copper are vaporized."

    That was my suggestion and I was dead wrong about that. I admit that I never took note of the approach speed -- which is on the same order of magnitude as for a meteorite strike to Earth. I was actually surprised that this speed was attempted, because for objects in space -- which are all traveling in the same direction and at the same speed -- the speed of impact is determined by the escape velocity of the object. For Earth this is 25,000 miles per hour, but for smaller objects it is much less. For the Moon this is 5,000 miles per hour. For an asteroid sized comet this would be a little more than nothing.

    Also, I have seen nothing more anywhere of all the copper molecules which should have been part of the initial impact explosion.

    ".. [the copper molecules] will provide a future site of any of the sporadic bursts of plasma that the comet now undergoes periodically."

    After the initial hot spot, material was noted as being ejected straight up in a column. That is certainly not the mark of impact ejecta; it is the mark of a cathode strike. This was correctly predicted by Thornhill. NASA might suggest later that this means that the probe bored a deep hole in the snow and ice, like a well or a gun barrel, which 'shaped' the initial ejecta.

    A conical shaped ejecta started after the initial appearance of the hot spot, and became increasingly larger with time. Although this could be understood as a large and deep hole made in the surface, it could also be a shallow crater whose size is progressively being enlarged by electrical sputtering at the edges of the crater. The conical ejection seemed to be side-lighted by the Sun. We will have to see if this stops or continues.

    "More energy will be released than expected because of the electrical contributions of the comet."

    "Copious X-rays will accompany discharges to the projectile, exceeding any reasonable model for X-ray production through the mechanics of impact."

    Thornhill was certainly correct in this. Flandern did not anticipate this, because there was no electrical interaction presumed. The sustained flare after impact amazed all the researchers. They have had to go to extremes to explain it.

    No mention has been made yet of spectral analysis. As with Halley's Comet in the 80's, an X-ray source will be identified, and then simply neglected.

    "In the event of a small impact crater, NASA will come up with a new theory of super-hard ices in space, or suggest a 10 foot deep impenetrable crust of solidified rock."

    NASA has in fact suggested the opposite, namely that the probe hit a soft outer layer before being crushed (in actuality 'vaporized') by deeper harder material ("ice"). The suggestion follows from the massive conical 'flare' which appeared and enlarged after impact.

    "Because the impact area is in sunlight and thus facing the solar wind of incoming protons, more water molecules will be produced by combination of protons with the oxygen ions than what is normally found in the outer reaches of the tails of comets."

    Did I say this? This clearly has turned out to be untrue -- much less water molecules are being produced than expected.

    "The discharge and/or impact may initiate a new jet on the nucleus and ... could even abruptly change the positions and intensities of other jets."

    It was initially claimed that the relocation of jets did not happen. It was later claimed that the relocation of jets did happen. Actually, no-one took note of any of this, for it was certainly not a concern of the accepted model of a comet. But the intensity remained the same. Two weeks later the comet had returned to the sporadic bursts of plasma which it exhibited before the impact.

    The Aftershocks -- A Week Later

    NASA keeps talking of snow and ice in their press releases. Other sites investigating the impact have other things to say, at time in contradiction.

    The first images returned from the Deep Impact fly-by spacecraft showed a small fireball followed by a much larger, incandescent flash that engulfed one end of the comet Tempel 1. Observatories on the ground reported that the explosion brightened the comet by a factor of five within 15 minutes of impact.

    It is really strange how the flare expanded quite slowly -- as if the edges of the crater were on fire. But this is entirely expected as an electrical phenomenon.

    The impact sent up twin plumes of debris, the first appearing as a narrow column that cast a long shadow across the comet. Another plume appeared seconds later on the heels of a brighter explosion, then fanned out in a star shape.

    Co-investigator Pete Schultz said the twin flashes showed that the impactor encountered softer, layered material on the comet's surface then hit a thick, hard crust. (Sydney Morning Herald, July 6)

    A comet is composed of two parts, the larger coma, which glows in glow-level plasma discharge, and the rocky interior, called the nucleus, which is the source of the coma. The initial plume is probably the ionization of the trajectory of the impactor, made visible with a glow-discharge plasma expulsion. It is not continued impact debris, which would create a spherical expulsion of material.

    The Deep Impact project investigator Michael A'Hearn said Friday that the major surprise of the mission was finding that the dust churned up by the collision was more like talcum powder than beach sand.

    Most scientists expected the surface of the comet to be covered with ice. Scientists say the new finding suggests that the comet was formed gradually. (Voice of America, 9 July 2005)

    Scientists studying the Deep Impact collision using NASA's Swift satellite report that comet Tempel 1 is getting brighter and brighter in X-ray light with each passing day.

    The X-rays provide a direct measurement of how much material was kicked up in the impact. This is because the X-rays are created by the newly liberated material lifted into the comet's thin atmosphere and illuminated by the high-energy solar wind from the Sun. The more material liberated, the more X-rays are produced. (source)

    X-rays are produced by intense concentrated electrical arcing, and by interaction of the ionized material with the incoming solar wind, not by dust lifted into space. [Added Note: It has been pointed out to me that the solar wind probably has nothing to do with this. If silicates were released from arcing, and electrostatically repelled from the arc site, the surplus of electrons available from the comet, at the same location, would be enough to account for the production of X-rays.]

    Mike A'Hearn of the University of Maryland and Pete Schultz of Brown University, attempted to explain some of their preliminary impressions of the images and data.

    The most obvious conclusion that could be drawn from a first look at the data is that the nucleus of the comet did not look like they expected it to, an elongated body similar to Comet Borelly. "There is a lot of topographic relief.

    There are things on this comet that look a lot like impact craters to many of us. It looks very different from Wild-2 or Borelly. We don't understand what this means. This comet has had an orbital history that looks pretty much similar to Borelly and yet it looks totally different."

    (continued:) "At the moment of impact, you heat materials to extremely high temperatures. Some of that is heated vapor. Some of that is melt droplets from within the crater itself. It is like a flashbulb -- material that is glowing so brightly that it illuminates its own picture."

    Such an incandescent flare had been visible in impact experiments he performed at the NASA Ames Vertical Gun Range facility in order to prepare for the Deep Impact encounter. In fact, Schultz explained, those experiments had contributed to the design of the image sequence for the impact; because of the possibility of an impact flare, the flyby spacecraft was instructed to take images at a high frame rate, once every 50 milliseconds (or a rate of 20 frames per second).

    The flare is visible in only one of those frames, meaning that the flash lasted for less than 50 milliseconds after the impact. [Actually, before impact.]

    Following the flare, Schultz said, there was a delay of a few frames before a plume of material can be seen to exit the impact point. The plume actually casts a shadow across the surface of the comet, a shadow that will eventually help the science team pin down the precise location of the impact crater. That few-frame delay indicates a layered structure for the comet, Schultz explained. "My guess is there was soft layering on top, [the impactor] went down, and finally got in contact with ices."

    The vaporization of ices likely produced that narrow plume. Following the plume, a broad curtain of slower-moving material can be seen to spread out from the comet. "The initial flash is an umbrella-like vapor plume. And then we see the large column. And then the curtain. The curtain later on tells us that the crater is expanding slowly, like you would expect from loose material. (The Planetary Society, Emily Lakdawalla, July 4, 2005)

    The circular arc ("curtain") and the increasing size of the crater are expected from the 'machining' (electrical sputtering) action of a circular arc. A depression forms as material is removed by arcing, which relocates the arc to the raised edge of the depression.

    Results are still coming in, but so far the scientists report seeing only weak emission from water vapor and a host of other gases that were expected to erupt from the impact site. The most conspicuous feature of the blast was brightening due to sunlight scattered by the ejected dust.

    I should note the obvious, that if the plume represented dust illuminated by sunlight, there would have been a shadow. The circular plume casts no shadow.

    "It's pretty clear that this event did not produce a gusher," said SWAS principal investigator Gary Melnick of the Harvard-Smithsonian Center for Astrophysics (CfA). "The more optimistic predictions for water output from the impact haven't materialized, at least not yet."
    Astronomer Charlie Qi (CfA) expressed surprise at these results. He explained that short-period comets like Tempel 1 have been baked repeatedly by the sun during their passages through the inner Solar System. The effects of that heat are estimated to extend more than three feet beneath the surface of the nucleus. But the Deep Impact indicates that these effects could be much deeper.

    And now for some contradictory information...

    SWAS operators were puzzled by the lack of increased water vapor from Tempel 1. Post-impact measurements showed the comet was releasing only about 550 pounds of water per second - an emission rate very similar to pre-impact values, and less than seen by SWAS during natural outbursts in the weeks before the impact.

    SMA measurements corroborate the SWAS findings. Although the SMA wasn't tuned to frequencies of water emission, which are difficult to observe from the ground due to atmospheric water vapor, it watched for other chemicals such as hydrogen cyanide.

    SMA astronomers saw little increase in production of gases following the impact. Gas production rates remained so low that they could set only an upper limit on the total. (source)

    The Gemini North telescope on Mauna Kea successfully captured the dramatic fireworks display produced by the collision of NASA's Deep Impact probe with Comet 9P/Tempel 1. Researchers on Hawaii's Big Island ... concluded from the mid-infrared spectroscopic observations that there was strong evidence for silicates or rocky material exposed by the impact. (Gemini Observatory News Release, July 7)
    Scientists monitoring NASA's Swift satellite had a good view of Deep Impact's collision with Comet Tempel 1. Although the space-based observatory was designed to watch for gamma ray bursts, its instruments were handy for this observation since it can see in several wavelengths at the same time.

    One of its most important observations from the impact is a quick rise in ultraviolet light. This means that the impactor struck a hard surface, as opposed to something soft and snowy. (July 7, Joint Astronomy Centre)

    Summing up

    Two Weeks Later

    The only news is that NASA now claims that the comet was covered with "cosmic talc" which would account for the gigantic -- and totally unexpected -- clouds of "dust" after the impact, which subsided after a few days. NASA still does not know the size of the crater -- guessing 150 to 750 feet. Apparently the crater size has increased, as expected, from the initial guess of 30 feet.

    The relocation of the periodic bursts to the impact site have not happened. The ESO reports: The flare only lasted a few days, and two weeks later the comet had returned to its earlier intermittent flares, at old locations. The ESO also claims that the impact "has failed to free up a large quantity of untouched material from beneath the surface."

    Meanwhile, Thornhill has posted a summary of findings at [http://www.thunderbolts.info/tpod/2005/arch05/050719deepinterim.htm] and [http://www.holoscience.com/news.php?article=3kneumjj].

    Thornhill also suggested (in a previous post) that NASA is rapidly forgetting some things -- like the initial flash, and the magnitude of the blast of light. This last is being turned to "sunlight reflecting on fine dust" rather than the more obvious "electrons in a state of high excitation." Of course the fine dust will be there as the initial cathode strike sputters solid rock into tiny fragments -- but so will the electrons and ions. Thornhill also mentioned that data is being removed from NASA websites.

    Two Months Later

    Abstracted and partially quoted from Science News Sept. 10, 2005, an article by Ron Cowen. The hemming and hawing of the scientists speaks for itself. I apologize for the length of the following quoted material, but it is so interesting to see words wend their way around facts to do a complete conceptual reversal. After reading this you will ask, what is the hidden agenda? Some comments at the end.

    [Researchers at the University of Maryland, under contract to NASA] ... claim that now we are for the first time "directly measuring pristine material from deep inside a comet, material that has been locked away since the beginnings of the solar system," and note that the primary constituent of the comet may be dust particles finer than talcum power, and the comet may be "far more porous than a solid chunk of ice. Its structure is more fragile than that of a soufflé," quoting Jay Melosh of the University of Arizona in Tucson.

    These findings are presented at an American Astronomical Society's meeting in England, and as papers published in Science.

    "We simply don't have any idea how you go from ... tiny pieces of dust and ice, one-tenth to one-hundredth the width of a human hair, to building a comet," notes Lisse (U of Maryland).
    Just milliseconds after the impact, the spacecraft recorded a faint flash that faded away in less than a second. Melosh and his collaborators propose that the flash denotes the instant when the 1-meter-wide bullet, coming in at an angle of about 60° from the vertical, hit the surface.

    This was probably the movement of electrons reaching up to ionize the incoming path of the impactor. Oops, this is not the pre-flash; Lisse is talking about an after-flash.

    A fraction of a second later, as the bullet began boring into the comet, an incandescent, hot spray erupted, traveling about 10 km per second. "[That] explosion is so violent that everything in its path is boiled off and swept out," says Lisse.
    Consisting of searing vapor and droplets of melted silicate at a temperature of 3,800 kelvins, the spray was so bright that it completely overwhelmed the solid-state detectors on the flyby spacecraft, stationed about 800 km away. Infrared spectra indicate the droplets were 10 to 100 nanometers in diameter.
    The high-velocity spray, which lasted for less than a second, was most likely created as the copper bullet vaporized comet material some 20 to 30 m beneath Tempel 1's surface. The bullet melted or boiled about 10 times its weight in ice and rocky particles.

    I really doubt the 90 foot (30 meters) deep hole. It is not based on observations, but is based on calculations of the amount of material ejected, and assumptions about the density of the comet. At a later date the NASA researchers will claim a density of one tenth of Earth rocks. That would make the crater only 9 feet deep. Once 'calculated' at 90 feet, this will reappear in other statements as fact.

    ... the bullet left behind a slow-moving sound wave or shock wave. This shock wave, spreading gradually through the comet's interior for as long as 5 minutes, appears to have carved out a deep crater. "That's an indication that the comet is fluffy," Lisse notes, "In a more-solid object, the shock would have bored a shallower hole," he says.

    As I will repeat: the crater has not been seen.

    The wave kicked up a plume of cool, extremely fine dust that lingered for more than 40 hours. The shock ejected an estimated 10 million kg of material.
    Most of the dust lofted into space by the shock wave had an average velocity of about 1 meter per second. That low speed was still enough to overcome the comet's weak gravity, which is about one-millionth that of Earth, notes Jim Richardson of Cornell University.
    Richardson estimates that in 2 days, about 95 percent of the dust particles had fallen back onto the comet. Because the particles were so small -- most no more than 100 micrometers in diameter -- they scattered nearly all the sunlight falling on them, rendering the funnel-shaped plume opaque. "It was almost a solid fountain of dust," says Lisse.
    The dust shroud hid the crater gouged by the bullet during a critical period, the first 800 seconds after impact, when the craft's high-resolution camera would have had a close-up view of the comet. A'Hearn and his colleagues had intended to image the bottom of the crater to measure its depth and determine its composition.
    Team members are now debating whether they can see signs of the crater in close-up images taken by Deep Impact's high-resolution camera. A flaw discovered after Deep Impact's launch had left that camera with a less-than-perfect focus.
    During the last minute or so of the close-up images taken by Deep Impact, some of the dust had begun to clear. While the crater isn't apparent, the scientists got a blurry glimpse of the bottom part of the plume, Richardson says. From those observations, the researchers estimate that the crater is about 100 m wide and 30 m deep [the 90 feet deep hole], in good agreement with Spitzer Space Telescope estimates of the total amount of dust ejected.
    Those dimensions imply that the impact excavated cometary material that's pristine and primitive, from the earliest days of the Solar System, notes Melosh. A shallower crater would probably contain material altered by the sun. Warming during Tempel 1's repeated passages near the sun over thousands of years might have caused sudden eruptions of gas and dust and altered the composition of material several meters beneath the comet's surface, but not 30 m deep [the 90 feet deep hole again].
    Despite scientists' difficulties in imaging the crater, other observations reveal that Tempel 1 is extraordinary fragile, composed of small particles bound together only weakly.
    The depth to which the bullet penetrated, for example, attests to the fragility of the comet, Melosh adds. Had the comet contained denser, more strongly bound material, the bullet wouldn't have penetrated to a depth of 30 m [the 90 feet deep hole].
    By analyzing images of the dust plume taken by the Deep Impact craft 45 and 75 minutes after the collision, Richardson and his colleagues measured the expansion rate of the plume. That rate is controlled by the comet's gravitational field, so once the gravity of the comet is known, researchers can estimate its density.
    The expansion measured indicates that the comet is highly porous, with an estimated density just 60 percent that of solid ice, and less than one-quarter that of the lowest-density rocks on Earth.
    As weak as the comet's gravity is, it still managed to keep the expanding plume anchored to the surface during the entire 40 hours that it remained visible. That's another hint that the gravity is sufficient to hold together the comet as a loose agglomeration of particles.

    "Keeping it anchored" is another one of those iffy phrases. To the researchers the cloud is a glob of dust hovering over the comet. They cannot imaging how it is held in place after being ejected. The forward speed of the dust should have released it entirely from the gravitational grip of the meteor.

    The plasma people understand it differently. The particulate matter is ionized silicates -- electrically charged rock dust. They are repelled by each other, and therefore spread away from each other. That accounts also for their initial leap off the surface. But at the same time they are attracted to the negatively charged surface of the meteor and continue to hover.

    Melosh's calculations suggest that when the comet coalesced, it did so at pressures and temperatures too low for water to be liquid. Liquid water glues together dust and ice particles in many other materials.

    For the same reason it's hard to make a snowball on a day too cold to melt ice, the grains of ice and dust that make up Tempel 1 just barely stuck together. As the object grew in size, however, its gravity, although weak, held the pieces in place, conjectures Melosh.

    The spectra obtained from both the Deep Impact spacecraft and the Spitzer Space Telescope reveal that the composition and temperature of the plume remained the same from a few minutes to hours after the bullet hit. That's an indication, says A'Hearn, that the composition of the comet material remains the same from near the surface to 30 m down [the 90 feet deep hole].

    About the looks of the surface of the comet, the following was noted...

    "We have a resolution better than any previous mission to a comet," says Veverka. The pictures, which portray about one-third of the comet, show a puzzling variety of smooth and rugged terrains, he notes.
    Craterlike outlines on some parts of the surface indicate that, unlike other comets seen close-up, it's been repeatedly beat up by Solar System debris for eons. It's as if "the whole cratering history [of the Solar System] is preserved on its surface," says Veverka.
    Yet some other regions show a smooth, flat, 20-m-high line of cliffs that defies any ready explanation, Veverka notes. Some of the smoothing, he notes, may result from frozen material sublimating from the surface, exposing terrain that lies beneath but then falling back to create a fresh deposit.
    One possible explanation is that sunlight triggered an icy volcanic eruption meters below the surface. The erupting material, trapped underground, might have spread out horizontally in the porous interior, like the frosting between the layers of a cake.

    The strange behaviour of a very weak gravity, the glueing together of microscopic dust particles, the assumed 'baking' by the Sun, the older impact sites which have done no more damage to the soufflé than a mild indentation, the 'shock wave' which took five minutes to travel 50 yards, a plume of dust anchored by gravity, the suggestion of 'icy volcanic eruptions,' the deep penetration hole [the 90 feet deep hole] which has yet to be seen, and the repeated equipment failures -- these all speak of soufflé science.

    It is interesting that such diverse readings -- the plasma version and the dirty snowball version -- could be extracted from the same data. Yet all the data is there. The snowball version, however, lacks any substantial physics; the concepts are constantly undercut with inexplicable "surprises."

    I have a fair suspicion that NASA knows damn well that the projectile hit a giant rock, not a pudding of mushy snow, that the fireworks were an electrical explosion, and that the cloud of 'dust' was rock which had been vaporized in an electrical explosion.

    But this information should not enter the public domain, because it will cause unneeded anxieties. If people knew that comets indeed consist of solid rock, and additionally are capable of exploding electrically, there would be panic about what would happen if a comet ever approached Earth. The earlier idea of, "we'll just nuke it," would have to be removed from consideration if comets are solid rock and if we get the sort of energetic reaction that we have just seen with the impact of a mere 800 pound chunk of copper.

    Entertaining the idea that comets are just cotten candy keeps them nukable, makes everyone feel confident that we can control these objects, and extends research programs for NASA.

    Six Months Later

    In January 2006 a package from the space craft "Stardust" landed on Earth. I'll quote the leading paragraph from thunderbolts.info's MOTD..

    "The first results from NASA's Stardust mission are in, leaving mission scientists in a state of shock and awe. The tiny fragments of comet dust brought back to Earth did not accrete in the cold of space, but were formed under 'astonishingly' high temperatures."

    -- [http://www.thunderbolts.info/tpod/2006/arch06/060316stardust.htm]

    The stuff consists of silicates -- rock dust.

    Two Years Later

    Official papers were published in "Science" in 2005.

    In the book "The Electric Universe" (2007), Wallace Thornhill and David Talbott elegantly sum up the evidence of the two positions I mentioned above -- that comets are rocks, and that the interactions will be electrical -- for Comet Temple I and for 15 years of space research (along with other "electric universe" aspects).

    Water Flowing Underground

    NASA/Ames NEWS RELEASE Posted April 11, 2006

    CRAFT'S 2008 IMPACT TO LOOK FOR SIGNS OF SUBSURFACE ICE

    NASA/Ames to crash into moon

    The NASA/Ames officials said Monday that the Lunar Crater Observation and Sensing Satellite will blast into space in October 2008 on the same rocket that lofts a larger lunar orbiter.

    Once there, it will act independently, releasing an SUV-size probe that crashes into the moon's south pole with such force that the impact should be visible on Earth through a telescope.

    NASA scientists say the collision should excavate a hole about a third of the size of a football field and hurl 2.2 million pounds of debris into space. The mother ship that released the probe will fly through the plume and look for traces of water ice or water vapor -- similar to NASA's Deep Impact mission last July, which blasted into a comet.

    Water is the key ingredient for supporting a future inhabited base on the moon, a goal of the Bush administration.

    "Establishing research stations on the moon will give us the experience and capabilities to extend to Mars and beyond," Ames' robotics deputy program manager, Butler Hine, said in a press release.

    The lunar orbiter will circle the moon for at least a year, mapping the surface, searching for water and scouting for potential future landing sites for astronauts.

    If ice is found, it could be melted and the water used to help make rocket fuel or oxygen, making a possible return to the moon -- and human occupation -- "much more cost-effective," Hine said.

    "Once in a Lifetime"

    Under the rocks and stones/ there is water underground.

    Letting the days go by/ let the water hold me down
    Letting the days go by/ water flowing underground
    Into the blue again/ after the money's gone
    Once in a lifetime/ water flowing underground.

    Same as it ever was...Same as it ever was...Same as it ever was...
    Same as it ever was...Same as it ever was...Same as it ever was...
    Same as it ever was...Same as it ever was...

    -- Talking Heads (1980)

    It would make as much sense for NASA to have said, "We know the green cheese is there; it's just well hidden."

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