By Nell Greenfieldboyce, NPR
NASA is about to launch an unprecedented mission to knock an asteroid slightly off course.
In the first real-world test of a technique that could someday be used to protect Earth from a threatening space rock, a spacecraft is scheduled to blast off from Vandenberg Space Force Base in California on Tuesday at 10:20 p.m. PST.
The golf-cart-size spacecraft will travel to an asteroid that’s more than 6 million miles away — and poses no danger to Earth — and ram into it. Scientists will then watch to see how the asteroid’s trajectory changes.
NASA has identified and tracked almost all of the nearby asteroids of a size that would cause world-altering damage if they ever struck Earth. For the foreseeable future, none that big are headed our way. But there are plenty of smaller asteroids, the size that could take out a city, that still haven’t been found and tracked.
It’s a space rock of that smaller size that the DART mission — short for Double Asteroid Redirection Test — will take head-on.
It might sound like a movie plot, but it’s not
“A lot of times when I tell people that NASA is actually doing this mission, they kind of don’t believe it at first, maybe because it has been the thing of movies,” says Nancy Chabot, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory.
Movies like Armageddon or Meteor typically feature a surprise, imminent killer asteroid, and saving humanity invariably requires blowing it to pieces with a nuclear bomb.
In reality, messy and unpredictable nuclear weapons aren’t the preferred choice of planetary defense experts, who would much rather identify dangerous space rocks way in advance of any possible collision and use more controlled methods to alter its path.
“The right time to deflect an asteroid is as far away from the Earth as we can,” says Lindley Johnson, NASA’s planetary defense officer. “The strategy is to find these objects not only years but decades before they are any kind of an impact hazard to the Earth.”
With enough advance warning, NASA could send out a spacecraft that would simply give an asteroid a little push, changing its course so that it no longer posed a problem. That’s the approach that NASA is testing out with DART.
“DART is demonstrating asteroid deflection. It is absolutely not asteroid disruption, which is how it goes a lot of times in the movies,” says Chabot, who serves as DART’s coordination lead.
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