Saving The Planet

< What are the chances that much of life could once again be snuffed out by a collision with an icy comet? Rather small, but there are plenty of asteroids in the heavens capable of causing devastation. Astronomers have identified more than 130 asteroids whose paths could intersect earth's orbit. Consisting largely of rock or iron, some are over a mile wide and could ram the earth at 65,000 km (40,000 miles) per hour. The odds of a strike within the next 50 years are probably less than one in 10,000. But whenever it does happen, the explosion could dwarf a nuclear bomb blast.

Until the space age, earthlings had no defense against such a threat. But now astronomers can determine years in advance if an asteroid will hit the earth. In theory, a nuclear missile could then be launched to rendezvous with the intruder, explode nearby and nudge it into a safe path. NASA, which spends under $1 million a year watching for collisions, will be a sponsor of the first International Conference on Near-Earth Asteroids next week in San Juan Capistrano, Calif., and is planning a seminar this year on asteroid avoidance. Still, the threat of a sneak attack remains. In 1989 a 250-m-wide (820 ft.) asteroid was discovered only after it had missed the earth by an astronomical eyelash -- less than 804,500 km (500,000 miles).