Other views of small comets debate
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December 9, 1997: The following press releases were issued by the Universities of Iowa, Arizona, and Washington in connection with papers being presented Tuesday, Dec. 9, at the American Geophysical Union meeting in San Francisco. They are presented here to provide readers with other views on the "small comet" debate. These viewpoints do not necessarily represent those of NASA. The telephone number for the AGU news room is (415) 905-1007.
Contact:Gary Galluzzo, Science Writer, University News Services, University of Iowa Office: (319) 384-0009
IOWA CITY, Iowa -- Two University of Iowa space physics researchers today, Tuesday, Dec. 9, presented a new study based upon photographs taken by cameras aboard NASA's Polar spacecraft as further proof of their 11-year-old theory that thousands of house-sized ice comets disintegrate in the Earth's atmosphere each day.
Louis A. Frank and John B. Sigwarth presented the study at the fall meeting of the American Geophysical Union (AGU) in San Francisco. The study shows dark spots (called "atmospheric holes" because of their appearance on film) captured in NASA photographs decrease in size and number as the Polar spacecraft's altitude and distance from the holes increases -- just what one would expect to find if the cameras are taking pictures of a real phenomenon. According to Frank, skeptics of the small comet theory who have maintained that the atmospheric holes are caused by electronic "noise" affecting the camera will now have to re-evaluate their position.
"This result is a marvelous confirmation of the reality of atmospheric holes," says Frank, a Fellow of the AGU and of the American Physical Society.
The latest study examines June 1, 1997 photographs of the Earth's upper atmosphere, comparing one set of pictures taken from between 3 and 5 Earth radii above the surface to another set taken at altitudes of between 5 and 8 Earth radii. A total of 5,650 atmospheric holes were observed in the images, however the high altitude photographs showed an 80 percent drop in the frequency of atmospheric holes in comparison to the low altitude data. Also a greater number of atmospheric holes were photographed during early morning hours than during evening hours.
At the spring AGU meeting in May, Frank revealed a series of photographs taken by cameras aboard NASA's Polar spacecraft as proof of the existence of the 20-to-40-ton ice comets that, over the age of the Earth, could have provided enough water to fill the oceans and plant the seeds of life. The pictures ranged from one of a small comet the size of a two-bedroom house disintegrating some 5,000 to 15,000 miles above the Atlantic Ocean to an image of light emitted by the breakup of water molecules from a small comet less than 2,000 miles above the Earth. Frank and Sigwarth, who co-discovered the small comets and designed the three Visible Imaging System (VIS ) cameras aboard the Polar spacecraft, said the pictures proved the existence of the small ice comets, but some doubters remained. (Since then, a satellite trailing the Space Shuttle Discovery in August detected significant amounts of high-altitude water vapor, a finding that supports the small comet theory.)
"Despite all of the evidence that the atmospheric holes were a geophysical phenomenon and not an artifact of the camera, many members of the scientific community refused to accept the reality of the atmospheric holes because of the immense implications of the large fluxes of small comets in the vicinity of our planet," says Frank.
Frank first announced the small comet theory in 1986, after examining images recorded in photographs taken by NASA's Dynamics Explorer 1 spacecraft. A specially-made camera had been designed to take pictures of the northern lights, a mission it completed successfully when it captured the first images of the complete ring of the northern lights from above the north pole. But some of the images contained unexplained dark spots, or atmospheric holes. After eliminating the possibility of equipment malfunction and numerous other explanations, Frank and Sigwarth concluded that the atmospheric holes represented clouds of water vapor being released high above Earth's atmosphere by the disintegration of small ice comets.
They calculated that about 20 comets enter the atmosphere each minute. At that rate, the steady stream of comets would have added about one inch of water to the Earth's oceans every 20,000 years -- enough to fill the oceans over billions of years. The theory was immediately controversial, with people asking why such objects hadn't been observed previously. Frank countered that not only their small size -- 20-to-30-feet in diameter -- makes observation difficult, but also that water striking the upper atmosphere glows very faintly as compared to the bright glow of metal and rock in solid meteors.
Not until the 1996 launch of Polar, with its two sensitive visible light cameras and one far-ultraviolet light camera, was there a chance to photograph the small comets with greater resolution.
Further information is at the Iowa small comets web site.
Contacts: Alex Dessler, 520-621-4589, Jennifer Grier, 520-621-1507, David Kring, 520-621-2024, Alfred McEwen, 520-621-4573, Bashar Rizk, 520-621-1160, Timothy Swindle, currently collecting meteorites in Antarctica; after January, 520-621-4128, )
Earth's sky would sparkle like a Christmas tree, its air would hold at least 30,000 times more inert gas and its moon would be pocked with millions more bright-spot craters than spacecraft see if a prominently publicized small-comet theory were correct, scientists from The University of Arizona in Tucson report in the Dec. 15 issue of Geophysical Research Letters.
University of Iowa physicist Louis A. Frank and his former graduate student announced last May in a NASA news release and at an American Geophysical Union news briefing that images from their Visible Imaging System on the Polar spacecraft show Earth is showered by a steady stream of water-packed objects, small comets that bombard our planet at a rate of between five and 30 per minute. They published the results in the Oct. 1 Geophysical Research Letters. If true, the discovery would force a rethinking of the origins of the oceans, terrestrial life and the formation of the solar system.
In five independent studies to be published Dec. 15, scientists including three teams from The University of Arizona conclude that theoretical calculations and observational evidence rule out the small-comet hypothesis.
If the small-comet theory were correct, the Earth's sky would be a continual display of bright clouds and flashes, according to calculations by Bashar Rizk and Alex J. Dessler of the UA Lunar and Planetary Laboratory. If 30,000 small comets bombard Earth daily, as the theory says, constant meteor-like displays would be visible even during the day.
The expanding cloud of tiny ice particles that small-comet theory suggests is created when a 30-ton, 40-foot-diameter comet breaks up high in the atmosphere would have a brightness somewhere between that of Venus and the full moon, Rizk and Dessler calculate. (Dessler in the late 1980s published a review of several earlier scientific studies that rigorously tested small-comet theory.)
If, as small-comet theory says, a small comet strikes Earth about every three seconds, it would be visible for at least a minute to the naked eye, readily seen by anyone looking up, Rizk and Dessler add. "Where are they? We should see them," the LPL researchers puzzle.
"A whole-Earth flux of 20 comets per minute implies the sudden appearance of at least two bright patches of light every five minutes," they report in GRL. "The two-hour periods after sunset and before sunrise ought to produce the most spectacular sightings intermittent punctuations of bright, rapidly moving points of light." Twilight would be much more exciting in Tucson, Cairo, Sydney, Capetown and other communities, say Rizk and Dessler. Citizens of Fairbanks, Montreal, Moscow and Stockholm would be treated to near all-night meteor shows, they add.
Small-comet theory requires that the bombarding comets were formed in very cold regions far the from sun, Timothy D. Swindle and David A. Kring of the LPL note in their paper. Comets that formed far out in space condensed from the same dust and gas that accreted into planets, trapping "noble" gases in the same ratio as the sun and the rest of the solar system. Noble gases are inert, or non-reactive gases, not easily removed from the atmosphere. They include argon, krypton, xenon, as well as the more common nitrogen, helium and neon.
Swindle and Kring analyzed how much noble gas the small comets would have delivered to Earth's atmosphere over the lifetime of the solar system. "We know that if the Earth's atmosphere were bombarded according to small planet theory, it would have a dramatically different composition," Kring said in an interview.
At the current rate of supposed small comet bombardment, Earth should have 500 times as much krypton and xenon and 30,000 times as much argon in its atmosphere, Swindle and Kring calculate. Put another way, all the krypton and xenon in Earth's atmosphere would have been delivered by small comets in 10 million years. All the argon present would have been added in 100,000 years. The scenario for Mars' atmosphere is an even more enigmatic: Small comets would have delivered the known Martian inventory of krypton and xenon in 500 years and the known inventory of argon in about 60,000 years.
Either the rate of supposed small-comet bombardment is today 30,000 times greater than it has been over the 4.5-billion-year lifetime of the solar system, or the comets formed much nearer the sun, about the distance of Jupiter, for the theory to fit the observed noble gas inventory, Swindle and Kring conclude. Comets can be greatly depleted in noble gases if they form closer to the sun, near Jupiter. "The problem with that idea is that it is completely inconsistent with several other physical conditions that Frank's team require to explain other features of their hypothesis," Kring said in the interview.
If the small-comet hypothesis is right, a small comet hits the moon at a rate of almost one per minute, Jennifer A. Grier and Alfred S. McEwen of the UA Lunar and Planetary Laboratory report in their paper. That is, scientists should see evidence of 400,000 comet hits on the moon annually.
Even a small, low-density comet would excavate a crater at least 50 meters in diameter and spread bright ejecta over an area of at least 150 meters in diameter, Grier and McEwen calculate. (The lunar surface darkens over time; the underlying, unexposed soil is lighter in color.)
Grier and McEwen compared Apollo 17 images taken in late 1972 to Clementine images taken 22 years later for a 52,000 square-kilometer area of the moon, which is about half the size of Kentucky and more than one-tenth of one percent of the lunar surface. Any crater and bright spot seen in the 1994 Clementine images but not visible in the 1972 Apollo photos might record a small impact or hit.
Each of the 3,920 bright spots seen over the study area in 1994 by the Clementine spacecraft was also recorded by Apollo. If the small-comet theory were correct, Clementine imaging should have discovered more than 10,000 new bright impact spots over this area.
Grier and McEwen calculate from the spacecraft observations an upper limit of 33 impacts a year for the entire moon, not 400,000 hits per year as expected according to the small- comet hypothesis. Small comets with properties hypothesized by Frank's team are probably more than a billion times less abundant than predicted, Grier and McEwen further conclude.
In another research article published in the Dec. 15 Geophysical Review Letters, a team of researchers who use a Polar spacecraft camera similar to the Frank team's Visible Imaging System also report seeing the dark pixels, or black points, that Frank interprets as evidence for small comets. This team, however, concludes the dark pixels are an inherent camera feature, or "noise" rather than real features.
A fifth paper in the journal suggests meteorites as small as 50 centimeters in diameter create plumes of atmospheric gas that Frank and his team interpret as small comets. The large-scale analogy to this phenomenon is the Comet Shoemaker-Levy impacts on Jupiter, they report.
Giant snowballs in space? No, says researcher, they're simply black snow on the TV screen
Contact: David Brand, UW News and Information. Phone: (206)-543-2580. Fax: (206)-685-0658.
San Francisco -- When University of Iowa space physicist Louis Frank presented his evidence last May, he had much of the science community shivering with anticipation. He claimed to have discovered 20- to 40-ton cosmic snowballs, the size of houses, pelting the Earth at the rate of 30,000 a day. What's more, Frank presented images he had captured of the giant snowballs.
But the snowballs may not exist. University of Washington geophysicist George Parks has analyzed Frank's ultraviolet (UV) camera images and has concluded that the white snow in space is no more than black "snow" on the television screen.
After a close analysis of one hour of data supplied by Frank, Parks says he and his collaborators are certain that Frank has been looking at "instrument noise." It is very similar, says Parks, "to the static you hear on your hi-fi."
Frank and Parks will debate the real vs. phantom snowballs here today at the fall meeting of the American Geophysical Union in San Francisco (Dec. 9 at 4 p.m.).
Frank first proposed his theory of the cosmic snowballs -- actually small comets -- in 1986, but the idea was widely discredited. Then, earlier this year, he presented evidence from the Polar satellite, which carries an instrument that can produce both UV and visible light images. Frank compared the same spots on both types of image and concluded that these were clear evidence of the existence of the comets.
Parks says that at first he was "agnostic" towards Frank's data. But when he saw the far more detailed images from the Polar camera he became suspicious. It was simply unlikely, he says, that the clusters of spots on the images could have been caused by snowballs in space. Parks began an analysis of his own images taken with the Ultraviolet Imager (UVI) on the NASA Polar satellite. There he found the same dark spots that Frank had found on his images.
He grew even more uneasy about Frank's analysis when he found that the UVI had recorded the same dark spots while pointed at a UV light in the laboratory.
When Parks began a minute examination of the images, made by breaking the clusters of spots down into tiny picture point, or pixels, he found statistical evidence that he was seeing not real events, but what he calls an "instrument artifact."
After Parks had detailed his analysis in an article for Geophysical Research Letters, Frank released one hour of data that overlapped with Parks' UVI images. Parks has made a comparison of the two and now believes, even more emphatically, that Frank has been attempting to interpret background noise.
What is causing the spots on the images? Park blames the very complexity of the cameras themselves, which consist of a number of parts, including optics, an image intensifier that includes a device for multiplying electrons, a TV screen and a light-gathering charge-coupled device. Parks suspects that the dark spots change character as the camera's high voltage is varied.
Parks claims that Frank has taken complex images and selected only one tiny area as evidence of the comets' existence. "He never shows the full image because it always looks corrupted by noise," he says.
Is Parks then denying the existence of cosmic snowballs? "The burden is on Frank, he's got to prove they exist," Parks says. "He is seeing things that are scientifically not permitted. It would, for example, be easy for me to say these dark spots are UFOs, but it would be up to me to prove it."
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