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Asteroid Insurance

Remember we told you the Wide-Field Infrared Survey Explorer (WISE) would be good at spotting near-Earth asteroids?Well, it is. And it has.Here (the red dot at center) is WISE's first find, a half-mile-wide chunk of rock called 2010 AB78, currently about 98 million miles from Earth. It's no threat,...

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Remember we told you the Wide-Field Infrared Survey Explorer (WISE) would be good at spotting near-Earth asteroids?

Well, it is. And it has.

NASA/ JPL-Caltech/UCLA

Here (the red dot at center) is WISE's first find, a half-mile-wide chunk of rock called 2010 AB78, currently about 98 million miles from Earth. It's no threat, although astronomers will continue to keep an eye on it.

Speaking of which, the National Academy of Sciences weighed in last week on NASA's plans to identify potential Earth-crossing space rocks and (possibly) destroy any that pose a danger.

Searching is a choice between money and time, says the Academy. Tracking 90 percent of the objects down to 140 meters in size (which would cause regional damage but only happen on average every 30,000 years) could be done with existing and planned ground-based telescopes, but might take another 20 years. If we're not comfortable with those odds and want the job done faster, we could build a dedicated space-based telescope. But that would cost hundreds of millions of dollars, far more than the $4 million a year NASA currently spends to watch out for asteroids. And nobody's rushing to increase the space agency's budget.

What if we were to see a big rock headed straight for us? The Academy's verdict is sobering. "Unless a large flotilla (100 or more) of massive spacecraft was sent as impactors, nuclear explosions are the only current, practical means for changing the orbit of large NEOs." Methods have been proposed to slowly push or pull on an asteroid in order to deflect it from Earth's path. Unfortunately, we'd need extremely long (multi-decade) warning times to make this happen in the case of large, civilization-threatening objects. And for warning times shorter than a year or two, civil defense (run away!) might be the only practical option.

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