David Braun reports in the National Geographic News that scientists have identified a thousand-yard-wide asteroid that may be heading for a collision with Earth 878 years from now.

Using radar and optical measurements made over the past 51 years, researchers have calculated that there is up to a one-in-300 possibility that Asteroid 1950 DA will slam into the Earth on March 16, 2880. ?We calculated the probability of collision based on what we know about the physical aspects of the asteroid and many other factors,? says Jon Giorgini of NASA?s Jet Propulsion Laboratory at the California Institute of Technology in Pasadena. ?As we get more information we will be able to adjust the level of probability up or down.?
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After our near-miss with an asteroid on March 8, an Australian government official dismissed a plea by scientists that his country should spend money searching for potentially threatening asteroids that can only be spotted from the Southern Hemisphere, calling it a ?fruitless, unnecessary, self-indulgent exercise.?

On the Australian TV show ?60 Minutes,? Peter McGauran said a lot of worries keep him up at night, but asteroids are not among them. ?I?m not going to be spooked or panicked into spending scarce research dollars on a fruitless attempt to predict the next asteroid,? he said.
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One of the largest asteroids known to have made a close approach to Earth flew past about 300,000 miles away on March 8, but nobody noticed it until four days later. When the object, which has been named 2002 EM7, passed closest to the Earth, it was too close to the Sun to be visible. A telescope operated by the Lincoln Laboratory at M.I.T. first recorded the new asteroid on March 12, as it moved away from the Earth and more of its bright side came into view.

Asteroids approaching from a blind spot cannot be seen by astronomers. If an object passed through this zone on a collision course with Earth, it would not be identified until it was too late for any intervention.
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If an asteroid impacted the Earth, the devastation would be so great that statistically, you are more likely to die from a space rock impact than in a plane crash. When asteroid 2001 YB5 flew past the Earth on January 7, 2002, it missed the planet by 300,000 miles, but at the speed the Earth is travelling in its orbit, that distance amounts to only a few hours.

So what is NASA doing about this? They?re practicing defensive wargames in space, so we can attack an incoming killer asteroid before it gets to us. Peter Schultz of Brown University says, ?We?re going to have some revenge on a comet called Tempel 1 with the Deep Impact mission.?
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