References: Key references for the lecture are given in the following list with a short description as to their relevance to the subject of small comets. The papers are listed in approximate chronological order of their publication date. Further relevant papers can be found in the reference lists of these papers.

  1. The original discovery of the atmospheric holes in the Dynamics Explorer-1 images and their interpretation in terms of small comets:
    • L. A. Frank, J. B. Sigwarth and J. D. Craven, Geophysical Research Letters, 13, 303-310, 1986.

  2. Detections of the small comets with the ground-based Spacewatch Telescope in Arizona:
    • C. M. Yeates, Planetary and Space Science, 37, 1185-1196, 1989.
    • L. A. Frank, J. B. Sigwarth and C. M. Yeates, Astronomy and Astrophysics, 228, 522-530, 1990.

  3. A popular trade book describing the small comet controversy and the reactions of the scientific community:
    • L. A. Frank (with Patrick Huyghe), The Big Splash, Birch Lane, New York, 1990, (Reprinted by Avon, New York, 1991.)

  4. A summary of the criticisms of the existence of atmospheric holes and small comets:
    • A. J. Dessler, Reviews of Geophysics, 29, 355-382, 1991.

  5. Comprehensive responses to the above criticisms of atmospheric holes and small comets:
    • L. A. Frank and J. B. Sigwarth, Reviews of Geophysics, 31, 1-28, 1993.

  6. Confirmation of the existence of atmospheric holes with the Polar spacecraft:
    • L. A. Frank and J. B. Sigwarth, Geophysical Research Letters, 24, 2423-2426, 1997.

  7. Discovery of oxygen trails from small comets at large distances from Earth:
    • L. A. Frank and J. B. Sigwarth, Geophysical Research Letters, 24, 2431-2434, 1997.

  8. Discovery of water fragments in the water clouds of small comets as they plunge into our upper atmosphere:
    • L. A. Frank and J. B. Sigwarth, Geophysical Research Letters, 24, 2435-2438, 1977.

  9. Comparison of images of the Moon with Apollo and the Clementine spacecraft in an attempt to find recent impacts of small comets:
    • J. A. Grier and A. S. McEwen, Geophysical Research Letters, 24, 3105-3108, 1997.

  10. Suggestion that a few of the atmospheric holes may be due to the impact of stony meteors in our atmosphere:
    • M. B. E. Boslough and G. R. Gladstone, Geophysical Research Letters, 24, 3117-3120, 1997.

  11. Findings of an unexplained water vapor layer in our upper atmosphere:
    • M. E. Summers and others, Science, 277, 1967-1970, 1997.

  12. Discovery of water frost on the Moon with the Lunar Prospector spacecraft:
    • W. C. Feldman and others, Science, 281, 1496-1500, 1998.

  13. Recent advances in studies of the possible influence of extraterrestrial volatiles on Earth's climate and the origins of the oceans:
    • D. Deming, PALAEO, 146, 33-51, 1999.

  14. Comprehensive investigation of atmospheric holes with the Polar spacecraft that eliminates the possibility of camera errors and firmly establishes the reality of atmospheric holes and their geophysical effects:
    • L. A. Frank and J. B. Sigwarth, Journal of Geophysical Research, 104, 115-139, 1999.

    Figure Captions

    • Figure 1. Image of an atmospheric hole as taken with the camera on board the Dynamics Explorer-1 spacecraft.
    • Figure 2. Diagram for viewing an atmospheric hole with a spacecraft orbiting Earth.
    • Figure 3. Sequence of events for the disruption of a small comet as it plunges toward our atmosphere.
    • Figure 4. Newspaper article reporting flying pigs in Indonesia.
    • Figure 5. University of Iowa scientist John Sigwarth viewing the cameras on the Polar spacecraft just before launch.
    • Figure 6. Detection of an atmospheric hole over Poland with a camera on the Polar spacecraft.
    • Figure 7. Discovery of the oxygen trail of a small comet as it moves across the North Atlantic toward East Germany.
    • Figure 8. Another oxygen trail, but over San Diego, California.
    • Figure 9. Two pictures of the large Comet Hale-Bopp, the upper picture for fragments of water molecules and the lower for sodium and dust.
    • Figure 10. Three snapshots of the water fragments in the water cloud of a small comet impacting our atmosphere.
    • Figure 11. A cartoon characterizing the emotional atmosphere surrounding the presentation of small comet results at national scientific meetings.
    • Figure 12. Diagram showing the motion of a water-bearing oceanic plate into the Earth's mantle.
    • Figure 13. Photograph of the Mexican volcano Paricutin in 1946.
    • Figure 14. Cartoon spoofing the many impacts of small comets into our atmosphere.
    • Figure 15. The recent discovery of an unexplained excess of water vapor at high altitudes in our atmosphere.
    • Figure 16. Icy clouds at high altitudes over the polar regions.
    • Figure 17. Award winner "Tex" Dessler suggesting to his master that he should look to the skies for evidence of small comets.
    • Figure 18. A bright meteor, a "fireball", streaking across our skies.
    • Figure 19. "Fluffy", the mascot of several critics of the small comets who insist that the Moon should "ring like a bell", even if the objects are fluffy small comets.
    • Figure 20. A photograph of an Apollo astronaut walking on the Moon's surface. Note the shallow crater to his right.
    • Figure 21. Photographs of the same area of the Moon during the Apollo mission (upper) and later with the Clementine spacecraft with obviously poorer resolution (lower).
    • Figure 22. The recent findings of water ice or snow in the polar region of the Moon. Blue indicates a significant presence of this water.
    • Figure 23. The risks of challenging scientific dogma.
    • Figure 24. Seasonal variations during the months of November through January for atmospheric holes (Polar spacecraft, upper panel, and Dynamics Explorer 1, middle panel) and for radar meteors (lower panel).
    • Figure 25. A diagram showing the inner disk and the Oort cloud of comets at great distances in the solar system, but still bound by the Sun's gravity.
    • Figure 26. Photograph of the building near Tombstone, Arizona which houses the Iowa Robotic Observatory.
    • Figure 27. The telescope with the protective roof of the building retracted so that the sky is viewed.
    • Figure 28. Sketch of the way the telescope is moved in order to "skeet shoot" the small comets.
    • Figure 29. Expectations for the imprint of a small comet trailing across the sensor of the telescope.
    • Figure 30. The exciting detection of a small comet in a photograph taken with the Iowa Robotic Observatory.
    • Figure 31. Scientific analysis of the event to show that the detection was not accidental.

    Acknowledgment. This research was supported in part at The University of Iowa by the National Aeronautics and Space Administration under Contract NAS5-30316 and Grant NAG5-3328.

    Illustration Acknowledgments. Fig. 1 L. A. Frank, J. B. Sigwarth and J. D. Craven, Geophysical Research Letters, April 1986; Fig. 2 L. A. Frank and J. B. Sigwarth, University of Iowa; Fig. 3 NASA; Fig. 4 Weekly World News, March 3, 1992; Fig. 5 J. B. Sigwarth, University of Iowa; Fig. 6 L. A. Frank and J. B. Sigwarth, Geophysical Research Letters, October 1, 1997; Fig. 7 L. A. Frank and J. B. Sigwarth, Astronomy Magazine, October 1998; Figs. 8-9 L. A. Frank and J. B. Sigwarth, University of Iowa; Fig. 10 L. A. Frank and J. B. Sigwarth, Geophysical Research Letters, October 1, 1997; Fig. 11 Frank Cotham, New Yorker; June 1, 1998; Fig. 12 A Teacher's Guide to the Geology of Hawaii Volcanoes, Hawaii Natural History Association; Fig. 13 K. Segerstrom, U.S. Geological Survey; Fig. 14 Ken Brown, source unknown; Fig. 15 NASA; Fig. 16 Science, Vol. 277, August 22, 1997; Fig. 17 EOS, Vol. 73, March 7, 1992, American Geophysical Union; Fig. 18 Akira Fujii; Fig. 19 "Fluffy" cartoon by W.B. Park, United Features Syndicate, Inc. 1985; Fig. 20 NASA; Fig. 21 J. A. Grier and A. S. McEwen, Geophysical Research Letters, December 15, 1997; Fig. 22 http://lunar.arc.nasa.gov/dataviz/datamaps/; Fig. 23 Source unknown; Fig. 24 L. A. Frank and J. B. Sigwarth, Journal of Geophysical Research, January 1, 1999; Fig. 25 L. A. Frank and J. B. Sigwarth, University of Iowa; Figs. 26-27 R. L. Mutel, University of Iowa; Figs. 28-31 L. A. Frank and J. B. Sigwarth, University of Iowa.

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