NASA Sees Comets Entering Atmosphere

Comet? Images from NASA's Polar spacecraft provide new evidence that Earth's upper atmosphere is being sprayed by a steady stream of water-bearing objects comparable to small comets.... Using Polar's Visible Imaging System (VIS), a research team led by Dr. Louis A. Frank of the University of Iowa in Iowa City has detected objects that streak toward Earth, disintegrate at high altitudes and deposit large clouds of water vapor in the upper atmosphere. — Goddard Space Filght Center, 28 May, 1997

...INCOMING OBJECT IMAGE: This image, taken by the Visible Imaging System (VIS) on NASA's Polar spacecraft in ultraviolet light, contains the trail of an object over the Atlantic Ocean and Western Europe on Sept. 26, 1996. The object was in sunlight but the Earth below was in darkness, so a map of the Earth has been superposed onto the image as a frame of reference. According to Dr. Louis A. Frank of the University of Iowa, the instrument's principal investigator, this time lapse image with a duration of 54 seconds shows a small comet the size of a two-bedroom house that disrupted 5,000 to 15,000 miles above the Earth. The Polar spacecraft was launched on Feb. 24, 1996, and is managed by the NASA Goddard Space Flight Center in Greenbelt, Md. (Photo credit Goddard and the University of Iowa.) (1)

Frank ..."The images show that we have a large population of objects in the Earth's vicinity that have not been detected before," said Frank, who designed the VIS instrument. "We detect these objects at a rate that suggest Earth is being bombarded by five to 30 small comets per minute, or thousands per day." Comets are known to contain frozen water and are sometimes called "dirty snowballs".

...The incoming objects, which Frank (right) estimates to be the size of a small house, pose no threat to people on Earth, nor to astronauts in orbit. "They break up and are destroyed at 600 to 15,000 miles above the Earth," Frank noted. "In fact, this relatively gentle 'cosmic rain' — which possibly contains simple organic compounds — may well have nurtured the development of life on our planet." (2)

Louis Frank's steadfast work to obtain these pictures is widely acclaimed. But not everyone accepts his interpretation of the data. There is not enough water apparent on the moon to satisfy some critics. Others complain that the seismometers on the moon haven't detected the impacts that these objects should create (3). And a paper in the 15 December, 1997, issue of Geophysical Research argues that the spots are merely artifacts after all (4). In fact, the controversy has created tension between Frank and the sceptics (5).

Supporting evidence comes from Robert Conway, a plantary physicist at the Naval Research laboratory, who announced on August 11, 1997, that his ultraviolet telescope on the Discovery Space Shuttle had detected unexpectedly high levels of hydroxyl in the upper atmosphere. Hydroxyl comes from water vapor, possibly delivered by the newly discovered snowballs (6-8).

To everyone's surprise, the objects seem to break up so much higher than they would if the atmosphere were the disrupting force. Frank proposes that Earth's magnetic field is the cause, but this mechanism needs further study. It will be interesting to see how the story unfolds. If they are real, the "gentle rain" of these objects could easily deliver viable bacterial spores and viruses to Earth.

What'sNEW since May 1997

Small impacts are reworking the moon's soil faster than scientists thought, Arizona State University (+Newswise), 12 Oct 2016.
Detections of Small Comets with a Ground-Based Telescope, by L. A. Frank and J. B. Sigwarth: v 106 n 3 Journal of Geophysical Research - Space Physics, 1 March 2001.
University Of Iowa's Louis Frank Uses Mathematical Data Analysis To Show Small Comets Are Real, ScienceDaily, January 6, 1999.
1998, May 30: An apparent seasonality strengthens the case for the small comets.
1997, December 9: Scepticism about the tiny comets... is growing.
1997, June 8: In a "Reply," Paul Lutus says that if the tiny comets were real, the moon would have a detectable atmosphere.


1. "Polar Spacecraft Images Support Theory of Interplanetary Snowballs Spraying Earth's Upper Atmosphere," NASA newsrelease 97-112, Goddard Space Flight Center, 28 May 1997.
2. ibid: NASA newsrelease 97-112.
3. Richard A. Kerr, "Spots Confirmed, Tiny Comets Spurned" p 1333-1334 v 276, Science, 30 May 1997.
4. Richard A. Kerr, "Tiny Comets' Spots Called Artifacts," p 1217-1218 v 278, Science, 14 November 1997.
5. Charles Petit, "Earth Bombed by Ice Balls, Scientist Says / But other experts at S.F. summit strongly disagree," p A6 San Francisco Chronicle, 10 December, 1997.
6. Associated Press, carried as "A good pelting for Earth" by The Commercial Appeal (Memphis Tennessee daily newspaper) p A2, 12 August, 1997.
7. Steven Young, "Satellite Backs Comet Bombardment Theory," Reuters, August 11, 1997.
8. Are Small Comets Dampening the Atmosphere? ScienceNOW, 15 August, 1997.

Related Reading

William J. Broad, "Tiny Comets May Have Big Impact," The New York Times, 29 May 1997.
William J. Broad, "Spotlight on Comets In Shaping Of Earth," p B7,B11, The New York Times, 3 June, 1997.
L.A. Frank, J.B. Sigwarth and J.D. Craven, "On the Influx of Small Comets into the Earth's Upper Atmosphere," p 303-306 v 13 n 4, Geophysical Research Letters, April, 1986.
L.A. Frank and J.B. Sigwarth, "Atmospheric Holes and Small Comets," p 1-28 v 31 n 1, Reviews of Geophysics, February, 1993.
L.A. Frank and J.B. Sigwarth, "Influx of small comets into Earth's upper atmosphere" [PDF], in Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms, Richard B. Hoover, Editor, Proceedings of SPIE Vol. 3111, p 238-248 (1997).
Richard A. Kerr, "Rising Damp from Small Comets?" p 1033 v 277, Science, 22 August 1997.
Kathy Sawyer. "Evidence of Cosmic Snowballs Starts Scramble for Explanations," p A03, Washington Post, 1 June, 1997.

Related Websites

Small Comets from the University of Iowa
The Original Discovery Excerpted from The Big Splash by Louis A. Frank with Patrick Huyghe, Birch Lane Press, 1990.
Is Earth Pelted by Space Snowballs? by R. Monastersky, ScienceNewsOnline, 31 May, 1997.
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