Asteroid 1950 DA is hurtling toward Earth at an "impossible" rate, and could threaten life on our planet in the year 2880. The rocky body seems to be defying physics, spinning so quickly that centrifugal force should be tearing the asteroid apart. Investigation of these unusual behaviors could assist researchers in their drive to protect Earth from potentially-hazardous asteroids.
Asteroids can often be collections of multiple bodies, held together through friction and gravity. Rotating once every 2.1 hours, this "rubble pile" should be torn apart by the forces on its component pieces. The upper limit for such formations is usually placed at 2.2 hours.
This rotational rate is so high, that the body experiences "negative gravity" at the asteroid's equator. A spacecraft landing there would instantly be flung off the surface of the asteroid, back into space.
Investigators believe the rocky body is held together through the action of van der Waals forces. This is a weak electromagnetic attraction between atoms and molecules that can cause dirt to stick to clothing. This force has previously been predicted in asteroids, but this study of 1950 DA is the first time the phenomenon has been seen in a real-life body.
Earth-threatening asteroids would need to be deflected or destroyed before they impacted our home planet, potentially causing massive damage. Using nuclear weapons on a solid body could be worse than doing nothing at all, as a solid body could break apart into a vast collection of smaller bodies that could impact all over the world.
Researchers have studied the idea of landing an automated craft on an asteroid, potentially pushing the body off a collision course with Earth. A rubble-pile asteroid may not be able to withstand the impact of such a maneuver, according to a new investigation into 1950 DA.
Rubble-pile asteroids could present a unique challenge for researchers looking for a way to save the planet from encounters with dangerous interlopers.
"With such tenuous cohesive forces holding one of these asteroids together, a very small impulse may result in a complete disruption," Ben Rozitis, a doctoral student at the University of Tennessee, said.
The Hubble Space Telescope captured asteroid P/2013 R3, as it fell apart into multiple pieces. This process may have been triggered by a collision with a smaller asteroid, astronomers believe. Rozitis and his team hold the belief this event may be a prime example of van der Waals forces coming apart in rubble pile asteroids.
The Rosetta spacecraft recently arrived at the comet 67P/Churyumov-Gerasimenko, where it will deploy the first lander ever targeted at such a body. A loosely-clumped surface there could suggest van der Waals forces play a role there, as well.