CONTRARY to a once popular theory, the Earth is not being pelted with
snowballs the size of houses.
Stephen Knowles and his colleagues at the Naval Research Laboratory in
Washington DC scanned the skies with the Naval Space Surveillance System鈥檚 powerful
radar to search for mini-comets thought to be dumping water into the atmosphere
(鈥淣ot a snowball鈥檚 chance鈥︹��, 12 July 1997, p 24).
The researchers found none, although they would have expected to see between 800
and 5000 if the snowball theory were correct (Journal of Geophysical Research,
vol 104, p 12 367).
The researchers are confident that the radar would have detected any comets
approaching low Earth orbit. 鈥淲e would have been able to see these things,鈥� says
Knowles. 鈥淚t would have been more fun if we did.鈥�
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