An asteroid held together by the van der Waals force

New Scientist : Asteroids are agglomerations of rubble. The smallest have so little gravity that if they were to spin with a period shorter than 2.2 hours, they would fly apart. That limit, derived in 1996 by Alan Harris of the Space Science Institute in Boulder, Colorado, has been breached by a 1.1-kilometer-wide near-Earth asteroid known as (29075) 1950 DA. Ben Rozitis of the University of Tennessee and his collaborators argue in a paper published this week in Nature that a type of weak intermolecular interaction known as the van der Waals force holds 1950 DA together. Although the asteroid poses no threat to Earth, its integrity remains weak. If such an asteroid were on target to hit Earth, deflecting it would have to be done in such a way as to avoid breaking it up and creating a swarm of smaller, yet still deadly fragments that continue toward our planet.