New NASA Mission Will Visit An Asteroid That Probably Hit Earth


A historic NASA mission that aims to collect a large sample from an asteroid will launch next month, in the hope of learning more about the formation and evolution of the Solar System. The spacecraft, OSIRIS-REx, will launch on September 8, 2016, and rendezvous two years later with the notorious asteroid 101955 Bennu, a threatening 500-meter (1,640-foot) impactor that will have a few close encounters with Earth in the 2100s. Bennu passes near Earth every six years, and in 2135 it will fly closer than the Moon.

“That 2135 fly-by is going to tweak Bennu’s orbit, potentially putting it on course for the Earth later that century,” principal investigator of OSIRIS-REx Dante Lauretta told the Sunday Times.

However, don’t be too worried. The chances of Bennu hitting Earth any time soon are tiny. NASA estimates that the chance of Bennu hitting our planet between the year 2175 and 2196 are about one in 2,700. An impact, though, would be equivalent to 60 times the most powerful nuclear weapon ever detonated, and it would have catastrophic global effects. So it’s a good thing it’s probably not going to hit us.

Aside from this, Bennu is of enormous scientific value. It has remained unchanged since the formation of the Solar System, and it might provide the answer to the question of where life on Earth came from.

“Bennu is a carbonaceous asteroid, an ancient relic from the early solar system that is filled with organic molecules,” added Lauretta. “Asteroids like Bennu may have seeded the early Earth with this material, contributing to the primordial soup from which life emerged.”

OSIRIS-REx will meet Bennu in 2018, when it will begin mapping the surface of the asteroid for 505 days. The map will be used to select a sampling site, and the probe will fly down and collect between 60 grams and 2 kilograms (0.13 and 4.4 pounds) with a robotic arm.

The sample will then be returned to Earth in 2023, where it will be analyzed. If everything goes according to plan, this will be the largest sample of asteroid material we have ever collected, and the biggest sample returned to Earth since the Apollo missions.

But sampling is not the only job for OSIRIS-REx. The spacecraft will assess the strength of the Yarkovsky effect, which is a force acting on rotating bodies that are not emitting heat uniformly. Since Bennu was discovered in 1999, this small but constant effect shifts its orbit by 160 kilometers (100 miles). This might not sound like much, but it could be enough to one day set the asteroid on a collision course with Earth.

[H/T: Sunday Times]

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