One of the most infamous near-Earth asteroids is held together by forces other than just gravity and friction. Researchers have found that the asteroid is a loose blob of particles that clot together much as Moon dust collects on astronauts’ spacesuits. Any mission to divert an asteroid on a collision course with Earth would need to take these newfound cohesive forces into account.
This means that gently nudging an asteroid onto a new trajectory is potentially a safer option than blasting it to smithereens, Armageddon-style. “You’d want to avoid interacting with the asteroid directly,” says Ben Rozitis, a planetary scientist at the University of Tennessee in Knoxville, and a co-author of the study.
Researchers have suspected that undetected cohesive forces help to hold some asteroids together, especially ‘rubble-pile’ asteroids, which are agglomerations of dirt and rock. Some of these rotate slowly enough for the gravitational attraction between the particles to hold them together.
But for faster-spinning asteroids, centrifugal forces would overwhelm the gravitational pull and rip the rocks apart. The fast-spinning 1950 DA will pass close by Earth in the year 2880. At one point, the odds of its hitting Earth were estimated to be as high as 1 in 300, but more recent observations have lowered that risk to 1 in 4,000.