http://www.reelartgallery.com/pages/a/armageddon_intl.html
Could it happen to us?
There are a bunch of dedicated research programs
whose goals are to discover Near Earth Asteroids:
asteroids that pass close to -- and could
potentially hit -- the Earth.
A few of the major programs are the
Spacewatch program
(at Arizona); the
Spaceguard programme
(UK);
the
LONEOS
program at Lowell Observatory; and the
LINEAR program
(MIT). Currently, the most productive
survey is the
Catalina Sky
Survey, at UA. Coming attractions include
Pan-STARRS
and then the LSST.
It is thought that there are about 1600 Earth-crossing
(potentially Earth-impacting) asteroids larger than
around 1 km (remember, the Chicxulub impactor was probably
around 10 km), of which only ~100 are known today.
These programs are all working to identify other
Earth-crossing asteroids.
Of course, if they ever find an asteroid that is going
to hit the Earth, what we would do about it is a
totally different question for which we do not
presently have any good answers. I guess we'll just
have to call Bruce Willis.
http://www.reelartgallery.com/pages/a/armageddon_intl.html