The notion that an asteroid or comet with enough energy to cause a national or global catastrophe may hit the Earth has, until recently, been regarded as in the realms of science fiction as opposed to science fact. Indeed, the impact origin of lunar craters has only been widely acknowledged in the second half of this century. However, studies conducted over the last fifteen years clearly indicate that such an event is not merely possible, but inevitable. The reality of major impacts in the solar system was starkly demonstrated in July 1994 when the fragments of Comet Shoemaker-Levy 9 collided with the planet Jupiter. The impact history of the Earth is now a matter of record, and there is no reason to assume that the threat is any less in the present than it was in the past; the only question is one of timing - when will the next major impact occur? Serious investigations into the nature and numbers of Near-Earth Objects (NEO) have only recently begun, and are far from complete, but the results of these studies already give considerable cause for concern, especially over the long term.

The assessment of any threat is based on two major factors:

• The likelihood of the threat becoming reality
• The consequences were it to do so.

The American Institute of Aeronautics and Astronautics (AIAA) Position Paper "Response to the Potential Threat of a Near-Earth-Object Impact" contains the following passage:

"If some day an asteroid does strike the Earth, killing not only the human
race but millions of other species as well, and we could have prevented it
but did not because of indecision, unbalanced priorities, imprecise risk
definition and incomplete planning, then it will be the greatest abdication
in all of human history not to use our gift of rational intellect and
conscience to shepherd our own survival, and that of all life on Earth."

Thanks to SpaceGuardUK for much of the content of this page.

Redesigned and hosted by Marc Chamberlin.