‘Rubble Pile’ Asteroids Are Nearly Impossible To Destroy

Australian-led research on an asteroid compared to a “giant space cushion” has provided insights into potentially saving Earth from a future impact. The experts studied three tiny dust particles collected from the surface of the Itokawa asteroid and returned to Earth by the Hayabusa-1 probe. The results showed that Itokawa was difficult to destroy and resistant to collisions, according to a study published Tuesday in the Proceedings of the National Academy of Sciences.

Located about two million kilometers from Earth and as large as the Sydney Harbor Bridge, Itokawa is classified as a debris asteroid. Unlike their monolithic counterparts, such asteroids are made largely of loose boulders and rock, said lead author and Curtin University researcher Fred Jourdan. “The survival time of Itokawa-sized monolithic asteroids is predicted to be only several hundred thousand years in the asteroid belt,” Professor Jourdan said. “The huge impact that destroyed Itokawa’s monolithic parent asteroid and formed Itokawa occurred at least 4.2 billion years ago.

“Such an astonishingly long survival time for an asteroid the size of Itokawa is attributed to the damping nature of the debris pile material. “In short, we found that Itokawa is like a giant space cushion and very difficult to destroy.”

The durability of rubble-pile asteroids was previously unknown, said co-author and Curtin researcher Nick Timms. This left experts unsure about the best defense strategies in case such an asteroid hurtled towards Earth. “Now that we have discovered that they can survive in the solar system for almost its entire history, they must be more abundant in the asteroid belt than previously thought,” said Professor Timms.