NASA's On Alert For Big Scary Asteroids. What About Smaller Ones? NASA has reactivated a mothballed spacecraft to look for big objects that might strike Earth. It's part of an increased effort to find potential hazards — but some scientists sizing up the sky think we should try harder.
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NASA's On Alert For Big Scary Asteroids. What About Smaller Ones?

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NASA's On Alert For Big Scary Asteroids. What About Smaller Ones?

NASA's On Alert For Big Scary Asteroids. What About Smaller Ones?

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
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This time last year, the headlines out of Russia were not about humans hurtling downhill headfirst but of an asteroid plunging into Earth's atmosphere. One chunk exploded over the Russian city of Chelyabinsk with the force of a 500-kiloton bomb. At least 1,000 people were injured. For his series Joe's Big Idea, NPR's Joe Palca reports the asteroid arrived without warning, and some scientists and inventors think it's time to be more proactive, planning for future asteroid strikes.

JOE PALCA, BYLINE: Not all asteroid encounters are cataclysmic despite what you see in the movies.


PALCA: In reality, the objects that hit Earth are quite a bit smaller. Most cause nothing more than a streak in the sky as they burn up in the atmosphere. But since some can be dangerous, NASA and other federal agencies have concluded it's time to adopt the Boy Scout motto: be prepared.

Part of being prepared is knowing what's out there, but that's not a trivial problem. There's a lot of sky out there, and asteroids, even big ones, don't necessarily shine brightly. But you can spot them if you happen to have an infrared telescope in space.

AMY MAINZER: Instead of seeing sunlight reflecting off of their surfaces, we're actually seeing the heat that they give off. We see them glow, essentially.

PALCA: Amy Mainzer is an astronomer at NASA's Jet Propulsion Laboratory in Pasadena and principal investigator for a spacecraft called WISE, which stands for the Wide-field Infrared Survey Explorer. And guess what? WISE has an infrared telescope. Even though space is a cold place, asteroids that come near Earth are warm.

MAINZER: They're sort of orbiting the sun at roughly the same distance as the Earth. So if you think about it, they absorb sunlight, and the sunlight warms them up.

PALCA: Making them glow in a way that WISE can see. NASA had actually shut the spacecraft off in 2011 when its main infrared detectors ran out of the coolant they need to work properly, but WISE has other detectors that are good enough to spot nearby asteroids. So NASA decided to switch it back on. Now it's called NeoWISE. Mainzer says it started hunting for asteroids just before last Christmas.

MAINZER: Basically six days after we started taking survey data, we found our first new asteroid.

PALCA: Right now the job of keeping track of all the stuff that might hit Earth falls to the International Astronomical Union Minor Planet Center. Timothy Spahr is the center director. Spahr says NeoWISE helps with the asteroid hunt in many ways.

TIMOTHY SPAHR: One of them is that there will be a few additional discoveries of near-Earth objects.

PALCA: But he says more important is that an infrared telescope can tell you how big an object is.

SPAHR: Getting the actual size of objects in space is notoriously difficult and effective impossible from ground-based surveys. And so having a space-based infrared telescope provides information that we simply don't get any other way.

PALCA: Obviously the big objects are the ones that could cause the most damage, but Mark Boslough thinks it would be a good idea to keep track of the smaller objects, too. Boslough is a physicist and asteroid impact expert at the Sandia National Laboratories in Albuquerque. He'd like to see an early warning system for asteroids that might hit Earth, something like what the National Hurricane Center uses to keep an eye out for dangerous storms.

MARK BOSLOUGH: I would propose a very similar system, where you have a survey to look at the sky, look for small objects, even small enough to not do any damage whatsoever, and you find these advance - hours, days, weeks in advance - and you issue an appropriate warning.

PALCA: Now an early warning about a Texas-sized asteroid that's going to destroy all life on Earth may not be all that helpful. But knowing about a smaller object could be. Boslough says the object that exploded over the Russian city of Chelyabinsk a year ago is an example of that.

BOSLOUGH: If we had discovered that in advance, we could have issued a warning, and we could have probably saved thousands of people from getting injured.

PALCA: The biggest chunk of that object exploded 20 miles up, so it didn't cause direct damage, but it did create a huge shock wave. Boslough says there's simple advice to prevent injuries in that instance.

BOSLOUGH: You just tell people to stay away from windows.

PALCA: And there were thousands of people...

BOSLOUGH: There were over 1,000 people, yeah, that were injured, you know, some very seriously from flying glass.

PALCA: Boslough admits it would be expensive to build that kind of early warning system, but it might just be cheaper and easier than calling in Bruce Willis and his pals to blow up a Texas-sized asteroid.


PALCA: Joe Palca, NPR News.


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