Today in frightening science news: researchers at UC Santa Cruz and Los Alamos National Laboratory have determined that if a giant asteroid is headed towards Earth, even detonating a small nuclear bomb may not be enough to stop it. The reason? If the blast isn't powerful enough, the asteroid fragments' own gravity could pull all of the pieces back together, T-1000-style -- in mere hours.]]>

Today in frightening science news: researchers at UC Santa Cruz and Los Alamos National Laboratory have determined that if a giant asteroid is headed towards Earth, even detonating a small nuclear bomb may not be enough to stop it. The reason? If the blast isn’t powerful enough, the asteroid fragments’ own gravity could pull all of the pieces back together, T-1000-style — in mere hours.

New Scientist reports:

If a sizeable asteroid is found heading towards Earth, one option is to nuke it. But too small a bomb would cause the fragments to fly apart only slowly, allowing them to clump together under their mutual gravity. Simulations now show this can happen in an alarmingly short time.

…

“The high-speed stuff goes away but the low-speed stuff reassembles [in] 2 to 18 hours,” [a researcher] says.

Fortunately, this means that a powerful enough blast could knock the asteroid pieces far enough apart that their gravity doesn’t pull them together, but: better get the maths right before somebody sets up us the bomb.

(via New Scientist)