They say to keep your friends close and your enemies closer. Apparently the old saying also applies in outer space, because NASA is planning to launch a probe to study an “Armageddon” asteroid that could one day come crashing into earth.

Bennu’s chance for impact

The asteroid is called Bennu and crosses Earth’s orbit once every six years. Bennu is approximately .3 miles in diameter and travels nearly 63,000 miles per hour. It was first discovered in 1999 and has gotten closer to earth with every recurring rotation. Scientists calculate that in 2135, Bennu will fly between the moon and the Earth—while that may seem like a large distance to us, it’s miniscule in space terms and is the solar system equivalent of threading a needle with a thick piece of thread. Even a small gravitational pull from earth could change the orbit and put Bennu on course to come crashing into earth.
It isn’t a sure thing that Bennu will collide with earth; in fact, scientists say there is only a small chance, around one in 2,7000, of it happening. It’s also likely that by the time Bennus is at risk for crashing into earth, technology will have developed so that scientists could potentially destroy an asteroid before it hits earth. But because impact from Bennu would be 200 times the strength of the atomic bomb dropped on Hiroshima, scientists are taking the threat very seriously.
“Bennu falls on the boundary, in terms of size, for an object capable of causing a global catastrophe,” says Professor Mark Bailey of Northern Ireland’s Armagh Observatory. Scientists aren’t take any chances when it comes to preserving the safety of earth’s population.

NASA’s plan of attack

To better understand the potentially devastating asteroid, this September, NASA will launch the un-manned Osiris-Rex probe to Bennu. The overall goal is to spend a year creating an extremely thorough map of every aspect of the asteroid and gathering rubble to bring back to earth. Bennu is a carbonaceous asteroid, which presents a unique opportunity for scientists to study an primal relic from the early solar system. Because the substance and molecules are so ancient, data from Bennu’s surface could give scientists a better idea of how the earth was formed and if there ever was life on Mars or other planets. It’s the space version of a time capsule for researchers.
“Asteroids like Bennu may have seeded the early Earth with this material, contributing to the primordial soup from which life emerged,” says Dante Laretta, a professor of planetary science at Arizona University. By studying the makeup of Bennu, scientists hope to have a better understanding of the early days of the solar system.
Because of difficulties with speed and orbit, the probe won’t actually meet up with Bennu until August 2018. It will take the year leading up to the rendezvous to gain speed as it orbits the sun before slingshotting around earth and using earth’s gravity to pull into orbital alignment with Bennu. Luckily, Bennu’s orbit is one of the best tracked in the galaxy, so researchers know where the asteroid is within 20 feet of its path. The speed and distance requirements mean that after the time it takes to map and gather samples, data from Bennu won’t be arriving back to earth until around 2023.

Yarkovosky Effect

For everyday global citizens, one of the most important aspects of Osiris-Rex’s mission will be the impact that comes from measuring and studying the newly discovered Yarkovsky effect, a force that can send asteroids careening around the solar system and possibly towards earth. Scientists blame the Yarkovosky effect for Bennu’s gradually changing path since 1999, which means the asteroid’s trajectory is even more difficult to track and predict than that of some other space objects because it is constantly changing, albeit in a fairly consistent pattern. The more information that can be gathered and studied about Bennu and the Yarkovosky effect now, the more information future scientists have if Bennu or another asteroid ever get dangerously close to earth.
The asteroid probe mission will cost an estimated $800 million, but the information it could provide to current and future scientists and astronauts could be priceless in teaching us where the earth and other planets came from. By taking the time to better understand our wider surroundings now, scientists could be prepared to help save the earth in the future.