Space Guard , Planet defence system

Essay by candyapples March 2004

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It is past time to get serious about planetary defense, The threat of Earth being on the receiving end of a cosmic calling card in the form of an asteroid or comet is real.

There is no question that an asteroid has Earth's name on it.

But where the rock is and when that impact is going to occur is unknown.

The threat posed to mankind by an impact of an asteroid or comet is now widely recognised as one of the most significant risks to human civilisation, yet there is no co-ordinated international effort to identify threatening Near Earth Objects (NEO's) or to deal with them once detected.

There is no Spaceguard program in Australia - government funding stopped in 1996. This is a real problem because who is watching the southern hemisphere?

The threat to Earth from impacts by asteroids and comets is very real. Impact craters have been found on much of the Earth's land surface, including the giant crater from the main impact that killed off the dinosaurs 65 million years ago.

The cratering rate over the past few million years reasonably matches that predicted from the small sample of "Near Earth Objects" (NEOs) found by astronomers to date.

A major NEO impact is an infrequent but highly destructive event. An impact by a 1 kilometre object could kill 1,500 million people. The chances of such an impact in the next 50 years are about 1 in 2000 (much "better" than the odds of four of a kind in poker). For a low-lying area on the shoreline of an ocean the risk of death from an impact is probably greater than that of an inland location due to the additional hazard of tsunami.

There are an estimated 2,000 NEOs larger than 1 kilometre.