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A small comet the size of a two-bedroom house caused a spectacular disruption 5,000 to 15,000 miles above the Atlantic Ocean on September 26,1996. The NASA Polar Spacecraft's Earth Camera recorded a far-ultraviolet image of the comet's disintegration, which was then superimposed on a view of Earth at the time of the event. The bright and long-lived trail ends over Germany.
In an discovery that might revise textbook explanations of how our planet obtained its water supply, the NASA Polar spacecraft has suggested that thousands of tiny ice-containing comets are pelting the Earth every day. These images support the hypothesis that Earth's water supply was created at least partly by house-sized, ice-filled comets, which strike the upper reaches of Earth's atmosphere and immediately disintegrate into water vapor.
University of Iowa scientist Louis Frank proposed this idea in 1986, after analyzing earlier satellite pictures which contained curious "holes" in the images. Frank argued that the holes actually represented small comets, but other scientists scoffed at this proposal, arguing that the holes merely represented noise. Now, Frank has been vindicated with the new, sharper images from NASA Polar Spacecraft, which contains state-of-the-art visible and ultraviolet cameras, which suggest that 5-30 of these comets enter the Earth every minute.
On December 31, 1996, the NASA Polar spacecraft recorded this nighttime image of the light emitted by the breakup of water molecules from a small comet. This image by the Low-Resolution Visible Camera on board the Polar spacecraft is composed of three consecutive snapshots of the event taken about six seconds apart. These intense glows are created at an altitude of less than 2,000 miles above Earth when sunlight illuminates the oxygen-hydrogen molecules formed after a comet's water molecules have been stripped of a hydrogen atom. A view of Earth at the time of the event has been superposed onto the image as there are no detectable emissions from Earth's nighttime atmosphere at the wavelength where these oxygen-hydrogen molecules glow.
Thanks to Louis A. Frank of the University of Iowa for providing the figures and much of the caption text.
This research was described on May 28, 1997 at the Spring Meeting of the American Geophysical Union in Baltimore, Maryland.