The Threat from Outer Space
Meteorite and Comet Impacts
A book by Peter Grego
Date of Publication: 1 October 1998
£10.99
Published by Cassell (Blandford)
ISBN: 0-7137-2742-X
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A collision with a comet's nucleus is the worst imaginable cometary encounter. Back in the 1950s, astronomers considered cometary nuclei to be small, flimsy and insubstantial objects - little more than "flying sandbanks" which were incapable of doing much damage to larger bodies in the solar system.
Fireball of 17 April 1984 (Peter Grego)
But we now know that even if cometary nuclei are in effect just large dirty snowballs, their impacts can cause a great deal of havoc - enough to give giant planet Jupiter a visible bruising.
A small cometary impact with the Earth would be akin to the above-ground explosion of a large nuclear device, and (apart from radiation) would produce many of the same devastating effects. Because three-quarters of the Earth is covered with water, the chances are that any future impact will happen over the ocean surface. This is likely to produce gigantic tidal waves which would swamp coastal sites many thousands of kilometres from the impact site. A continental impact would have the potential to cause grave loss of life, not to mention global after-effects which might include climatic change of unknown duration or severity.
In June 1908 it is believed that the impact of a tiny comet nucleus devastated a large but remote area of Siberia. It was by remarkable luck that this impact happened at one of the least-populated sites on the planet and no great loss of human life was reported.
