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The close approach also highlights the need to keep track of what’s out there, if for no other reason than to protect the planet.

NASA’s current count of near-Earth objects: just short of 10,000, the result of a concentrated effort for the past 15 years. That’s thought to represent less than 10 percent of the objects out there.

No one has ruled out a serious Earth impact, although the probability is said to be extremely low.

“We don’t have all the money in the world to do this kind of work” for tracking and potentially deflecting asteroids, said Lindley Johnson, an executive with the Near-Earth Object observations program in Washington.

Indeed, when asked about NASA’s plans to send astronauts to an asteroid in the decades ahead, as outlined a few years ago by President Barack Obama, Johnson said the space agency is looking at a number of options for human explorations.

One of the more immediate steps, planned for 2016, is the launch of a spacecraft to fly to a much bigger asteroid, collect samples and return them to Earth in 2023.

As for Asteroid 2012 DA14 _ discovered last year by astronomers in Spain _ scientists suspect it’s made of silicate rock, but aren’t sure. Its shape and precise size also are mysteries.

What they do know with certainty:

“This object’s orbit is so well known that there’s no chance of a collision,” Yeomans repeated during Thursday’s news conference.

Its close approach, in fact, will alter its orbit around the sun in such a way as to keep it out of Earth’s neighborhood, at least in the foreseeable future, Yeomans said.

Johnson anticipates no “sky is falling thing” related to next week’s flyby.

He and other scientists urged journalists to keep the close encounter in perspective.

“Space rocks hit the Earth’s atmosphere on a daily basis. Basketball-size objects come in daily. Volkswagen-size objects come in every couple of weeks,” Yeomans said.

The grand total of stuff hitting the atmosphere every day? “About 100 tons,” according to Yeoman, though most of it arrives harmlessly as sand-sized particles.

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