Jan. 6, 1999 IOWA CITY, Iowa -- Asserting that critics have been looking at the wrong data, University of Iowa space physicist Louis A. Frank has published a new paper supporting his "small comet" theory that about 20 snow comets weighing 20 to 40 tons each disintegrate in the Earth's atmosphere every minute.
The paper, which appears in the January 1, 1999 issue of the American Geophysical Union's (AGU) Journal of Geophysical Research-Space Physics, uses an automated mathematical formula to filter out electronic instrument noise from data gathered by NASA's Polar satellite. The result, says Frank and his UI colleague John B. Sigwarth, is a "hands-off" analysis showing that "instrumental effects were not major contributors" to the images of atmospheric holes. Using the mathematical formula, the two researchers found that the atmospheric holes photographed by the Polar satellite cameras:
o Increase in number when photographed from lower altitudes.
o Increase in number when photographed during local-morning time periods.
o Appear larger in size in satellite images when photographed from lower altitudes.
o Vary in number, depending upon the season.
"What critics of the small comet theory were analyzing was instrument noise," Frank says. "If you strip away the noise from the data, as they properly should have done, what remains clearly validates the reality of atmospheric holes. Our most recent paper is the only comprehensive paper on this topic and shows, without reasonable doubt, that the atmospheric holes are indeed a real phenomenon."
Frank says that the mathematical formula applied to the data screened out possible causes of electronic noise such as longer wavelength radiation, energetic electrons and uneven sensitivity -- or "hot spots" -- among camera instrument pixels. Significantly, he found mid-January 1998 data containing no atmospheric holes and used it as a baseline measurement.
"The period in mid-January during which no atmospheric holes were detected provided an excellent opportunity to have a very effective calibration series of images which were equivalent to an extensive post-launch laboratory calibration. These in-flight calibration images were extremely important in establishing the instrument noise performance without the presence of atmospheric holes and with the actual temperatures and operating voltages for the instrument. These images verify the accuracy of our computations of random hole rates," he says.
In a 1998 study, Frank and Sigwarth analyzed 1981 data collected by the Dynamics Explorer 1 satellite and compared it to data gathered by Polar in 1997, finding a mid-January lull in both sets of data. Despite the fact that observations of seasonal variations in atmospheric holes were made 16 years apart by different spacecraft carrying different cameras, criticism remained. Several papers refuting the theory were presented at the spring 1998 AGU meeting, one of them suggesting that measurements made by another satellite show that the atmosphere some 15 to 35 miles above the Earth is much drier than the small comet theory would suggest.
In December 1997, Frank presented a study at the AGU fall meeting showing that dark spots (called "atmospheric holes" because of their appearance on film) captured in June 1997 on Polar photographs decrease in size and number as the satellite's altitude and distance from the holes increases. Earlier, Frank had created a stir at the May 1997 AGU meeting when he revealed a series of Polar satellite photographs, ranging from a picture of a small comet the size of a two-bedroom house disintegrating thousands of 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 and built the three Visible Imaging System (VIS ) cameras aboard Polar, offered the pictures as proof of their theory.
Frank first announced the small comet theory in 1986, after examining images recorded in photographs taken by Dynamics Explorer 1. Frank and his colleagues had designed and built a special camera to take pictures of the northern lights, including 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 comets composed mostly of snow.
They calculated that more than 25,000 comets enter the atmosphere each day. 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. The controversy re-ignited after the 1996 launch of Polar, carrying two sensitive visible light cameras and one far-ultraviolet light camera, made it possible to photograph the small comets with greater resolution.
For further information, see:
o Small comet web site: http://smallcomets.physics.uiowa.edu
o Small comet website press release: http://smallcomets.physics.uiowa.edu/automated1.html
o Full text of JGR paper: http://smallcomets.physics.uiowa.edu/pdf/jan99_jgr.html
o New small comet photos: http://smallcomets.physics.uiowa.edu/newphoto1.html
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