à la carte 'Armageddon' by Asteroid

[humble3d]

à la carte 'Armageddon' by Asteroid



Bad news everyone: There are two (at least) completely different types of massive asteroid that could have a devastating effect on life on our planet, and it'll likely require two completely different strategies to divert them from an impact.

Diverting an asteroid has become one of the main goals of NASA in recent years, as it's going to attempt to lasso one and pull it into lunar orbit sometime in the next couple years. That's all well and good, except astronomers have just discovered that so-called "rubble pile" asteroids are made up of millions of bits of rocks loosely held together not just by gravity, but by newly-discovered "cohesive forces."

The problem, at the moment, is that we aren't exactly sure what happens if you try to divert an asteroid like that. In a paper published today in a paper published today in Nature, University of Tennessee researcher Ben Rozitis writes that gravity alone isn't enough to explain the existence of 1950 DA, a kilometer-long asteroid with a 1 in 4,000 chance of hitting Earth in the year 2880. Instead, the asteroid is held together much like a sand castle is, with scores of loose bonds between the rubble.

"This places the asteroid in a surreal state in which an astronaut could easily scoop a sample from its surface, yet would have to hold on to the asteroid to avoid being flung off," Daniel Scheeres, a researcher at the University of Colorado, Boulder, wrote in an accompanying Nature article.

It also places astronomers in the unenviable position of wondering what, exactly, to do if a huge rubble pile astroid looks like it's going to hit Earth. Conventional wisdom suggests that you ram a spacecraft (or a missile, or something very heavy) into it. But that might not work here, Rozitis told me.

"With one of these asteroids, if you do that, you risk breaking it up and turning it into several smaller objects that can still hit the Earth," he said.

In his article, Scheeres likened it to getting hit with a shotgun instead of getting hit with a missile, and it's unclear which would be better.

"Whether the impact from such a disaggregated asteroid would pose a larger threat to Earth has been a matter of debate in the scientific community," he wrote. "Whereas a single asteroid packs a larger punch, the shotgun spray from a disaggregated body may hit multiple sites across the globe."

At the moment, our best option is a theoretical and well-known spacecraft, known as a gravity tractor, that exists solely in science fiction at the moment.

"Basically, you place a heavy spacecraft near the asteroid, then use it to pull the asteroid off its impact point, which in this case would be Earth," Rozitis said. "We've got a good theoretical understanding of it, but there's still a lot of questions."

Indeed, several gravity tractors have been proposed by scientists, but none have been developed.

And still, scientists have to determine whether a given asteroid is a rubble pile or a solid one—tough when an asteroid is extremely far away. NASA better start planning a second asteroid mission for Congress to bitch about.

http://motherboard.vice.com/read/we-need-more-than-one-way-to-armageddon-an-asteroid