Asteroid Headed for Earth in 2880 Is Really Just a Clump of Rubble

Artist's impression of an asteroid.
Artist's impression of an asteroid.
Image: Flickr, Hubble ESA






"I was expecting to find a high-density metallic asteroid, as such an asteroid wouldn't require cohesive forces to hold itself together under its fast rotation," lead study author Ben Rozitis, an astronomer at the University of Tennessee at Knoxville, told "Instead we found the opposite!"

A rock pile in space



"We knew from previous work that this asteroid was rotating faster than it should be, and we wanted to know why," Rozitis said.


"We found a low-density rubble pile that traditionally would be unable to hold itself together unless cohesive forces were present," Rozitis said. "It's exciting because we've provided the first evidence that cohesive forces are important for small asteroids, which had only been predicted up until now."

These findings could shed light on how disks of gas and dust around newborn stars coalesce into asteroids, comets, rings, moons and planets, researchers say. "Cohesive forces will be present in every asteroid, and not just the fast-spinning ones," Rozitis said. "It is just easier to observe the effects of cohesive forces in the fast-spinning ones."

Asteroid mining and defense concerns


"Mining missions intend to visit small asteroids about 10 meters (33 feet) or less in size, as it is thought that they are predominantly solid bodies," Rozitis said. "However, cohesive forces enable such small asteroids to be rubble piles instead. A small rubble-pile asteroid would be harder to interact with and collect, as it can easily deform or break up when subject to external forces."


"The best way to mitigate an impacting asteroid is to nudge it slightly several years before impact so that it changes course," Rozitis said. "This can be done by hitting the asteroid with a fast and heavy spacecraft. However, by hitting a fast rotating asteroid held together by cohesive forces, you risk breaking it up into several smaller, hazardous asteroids. Therefore, with such an asteroid, you want to avoid interacting with it directly to prevent it breaking up. An alternative is to use a 'gravity tractor,' or a heavy spacecraft placed near the asteroid, which uses the force of gravity to pull the asteroid off course."

Future research can investigate fast-spinning asteroids of different compositions, "as the cohesive forces involved might vary with asteroid composition," Rozitis said.


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