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No. 92: Mar-Apr 1994

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Target Earth

Let Jupiter take care of itself! What about us -- Terra, the third planet? A February article in Sky and Telescope begins:

"Military satellites have been watching huge meteoroids slam into the Earth's atmosphere for nearly two decades."

Secret until recently, infrared scanner data from military satellites have detected 136 atmospheric explosions since 1975 with yields of 1 kiloton or more. There may actually have been as many as four times this number, because the satellites are programmed to look for unnatural events, such as nuclear detonations. They often ignore extraterrestrial projectiles.

Why aren't earthbound observers aware of all these atmospheric explosions? Because most are infrared events; few emit enough visible light to attract the attention of ground-based observers. However, two of these "secret" meteoric events might explain some Fortean phenomena recorded over the last two centuries.

April 15, 1978. Over Indonesia. A military satellite watched a colossal daylight fireball that, for one second only, would have rivaled the sun to anyone watching from the ground below and alert to such phenomena. The TNT yield was estimated at 5 kilotons.

August 3, 1963. Between South Africa and Antarctica. A huge airburst equivalent to a 500 kilotons was picked up by a worldwide network of acoustic detectors. The cosmic interloper this time was believed to have been a small asteroid about 20 meters in diameter.

(Beatty, J. Kelly; "'Secret' Impacts Revealed," Sky and Telescope, 87:26, February 1994. Cr. P. Huyghe. Also: Broad, William J.; "Meteoroids Hit Atmosphere in Atomic-Size Blasts," New York Times, January 25, 1994. Cr. J. Covey)

Comment. The Indonesian event mentioned above may be associated with the many recorded instances of transient brightenings of the entire sky (GLA14 in Lightning, Auroras, Noctural Lights ). The 1963 acoustic event might be related to the many mysterious booms or detonations heard down the decades, long before jet planes offended our ear-drums (GSD1 in Earthquakes, Tides, Unidentified Sounds ).

Both of the books just mentioned are described here.

From Science Frontiers #92, MAR-APR 1994. � 1994-2000 William R. Corliss