This is important as its composition will determine while kind of countermeasures would be most effective.
If it’s a loosely bundled collection of big rocks or even a giant bundle of powder, blasting it apart may actually increase its threat. Bennu is moving at 101,000km/h. Its fragments would continue to hurtle on — possibly increasing the chance of catching Earth with a ‘shotgun’ effect.
If it’s a seemingly solid mass, it will need to be punched — hard.
But there’s also real science to be learnt from the enormous mass of leftovers from the birth of our Solar System. Does it contain the very building blocks of life itself?
The idea is to put a series of warheads in an orbit just ahead of Bennu. The asteroid would then crash into them at speeds greater than 35,000km/h. The kinetic energy (battering ram effect) of such an impact alone is enormous.
But, if necessary, it could also be used to trigger nuclear bombs.
These would not strike the asteroid. They would be set off above its surface, vaporising the material there. This ejecta would thrust the asteroid in the opposite direction.
But even the largest warheads such missiles could carry would need to strike asteroid Bennu decades before it was due to pass Earth. That way, even a small nudge could accumulate to a huge safety gap at the critical time.
“Whenever practical, the kinetic impactor is the preferred approach, but various factors, such as large uncertainties or short available response time, reduce the kinetic impactor’s suitability and, ultimately, eliminate its sufficiency,” the researchers write.