Asteroid Bennu: NASA Wants to Use Nuclear Weapons to Deflect 1,600-Foot Space Rock

An artist's impression of Bennu. NASA lists 78 dates on which Bennu has a tiny chance of colliding with Earth. NASA Goddard

Scientists have designed a nuclear weapon–wielding spacecraft powerful enough to deflect a 1,600-foot asteroid currently circling the sun.

Set for multiple close encounters with Earth over the next hundred years, there is a chance—however vanishingly small—that the asteroid Bennu could one day collide with our planet.

Don't worry. NASA has a plan to save us all. And it involves nukes.

Very Small Risk of Collision

NASA lists 78 dates on which Bennu has a tiny chance of colliding with Earth. Taken together, they give an impact risk of one in 2,700—small but not impossible.

Asteroid impacts can be devastating. Some 66 million years ago, the impact of a 9-mile asteroid is widely believed to have wiped out most of Earth's dinosaurs. In 2013, a 65-foot asteroid entered the skies above Russia, exploding over Chelyabinsk Oblast. The blast caused extensive damage and injured nearly 1,500 people.

Scientists from NASA, the National Nuclear Security Administration and two Energy Department weapons labs have designed a spacecraft to deflect an asteroid. Their research was published recently in the journal Acta Astronautica.

Nuclear Explosion or Colliding Spacecraft?

This compilation of radar images shows Bennu, left, and a shape model of the asteroid. Michael C Nolan/Arecibo Observatory

Called the Hypervelocity Asteroid Mitigation Mission for Emergency Response, or HAMMER, the "impactor" spacecraft would be deployed to deflect a small asteroid with its own bulk. In certain cases, however, it would set off a nuclear weapon.

"If the asteroid is small enough, and we detect it early enough, we can do it with the impactor," physicist and study co-author David Dearborn of the Lawrence Livermore National Laboratory told BuzzFeed News. "The impactor is not as flexible as the nuclear option when we really want to change the speed of the body in a hurry."

In an ideal situation, lots of these spacecraft would fly into the path of the asteroid. As it would plow through them it would be pummeled by 22,000-miles-per-hour collisions. These collisions would hopefully slow down the asteroid enough to divert its trajectory.

"You have to be careful not to slow it down just enough to go from hitting the [side] of the Earth to hitting its center," Dearborn said.

The Growing Field of Planetary Protection

3_9_Bennu Orbit
The orbits of Bennu and the three inner planets, around the sun, as recorded September 7, 2016. JPL Small-Body Database Browser/NASA

Unfortunately for us vulnerable earthlings, HAMMER is a plan which may never be built. The proposal is one of a growing number of potential planetary protection efforts developed following a 2010 National Research Council report that called for the development of NEO hazard mitigation plans.

Researchers modeled their work on Bennu because the asteroid is the best-studied near-Earth object. It zipped past Earth in 1999 and again in 2005, but it won't have another close encounter until 2054, NASA predicts. In September 2135 it may come as close as one-third the distance to the moon.

"Smart people are taking this seriously and thinking carefully about what might be done," MIT impact expert Richard Binzel, who was not involved in the study, told BuzzFeed News. "These are reasonable ideas—well thought out."

"Hopefully we won't need an asteroid deflection plan," he added. "But until we search, we don't know."