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August 14, 2009

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NASA can't track all dangerous asteroids

NASA is charged with spotting most of the asteroids that pose a threat to Earth but does not have the money to complete the job, a United States government report says.

Congress assigned the space agency that mission four years ago, but it never gave it the money to build the necessary telescopes, according to the report released on Wednesday by the National Academy of Sciences.

Specifically, the mission calls for NASA, by the year 2020, to locate 90 percent of the potentially deadly rocks hurtling through space. The agency says it has been able to complete about one-third of its assignment with the current telescope system.

NASA estimates that there are about 20,000 asteroids and comets in our solar system that are potential threats. They are larger than 140 meters in diameter - slightly smaller than a sports stadium. So far, scientists know where about 6,000 of those are.

Rocks over 140 meters in diameter can devastate an entire region, said Lindley Johnson, NASA's manager of the near-Earth objects program.

Last month astronomers were surprised when an object bashed into Jupiter and created an Earth-sized bruise that is still spreading. Jupiter does get slammed more often than Earth because of its immense size and gravity.

When it comes to monitoring, the academy concluded "there has been relatively little effort by the US government." And the US is practically the only government doing anything at all, the report found.

NASA calculated that to spot the asteroids as required by law would mean spending about US$800 million up to 2020, Johnson said.

If NASA got only US$300 million it could find most asteroids bigger than 300 meters across.

At the moment, NASA has identified about five big objects that pose a better than one-in-a million risk of hitting Earth, Johnson said.

They are keeping their closest eye on a 130-meter diameter object that has a 1-in-3,000 chance of hitting Earth in 2048.


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