NASA's probe reaches asteroid that is a potential threat to Earth

NASA’s Osiris Rex arrives at potentially Earth-bound asteroid Bennu

Artist's rendering of OSIRIS-REX deploying its Touch-And-Go Sample Arm Mechanism

An artist's drawing of the OSIRIS-REx spacecraft near the asteroid Bennu.

The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft met Bennu on Monday after travelling through space for more than two years and over two billion kilometres, NASA said.

Choosing today's burn as the official arrival moment was somewhat arbitrary, but as good a time as any. OSIRIS-REx has had Bennu in sight since 17 August, and by mid-November, the asteroid was big enough to make out surface details, including a 55-meter-wide boulder Lauretta likened to a pimple.

As NASA studies these images the OSIRIS-REx team will decide on the best possible place to land.

The carbon-rich asteroid was chosen from some 500,000 asteroids in the solar system because it orbits close to Earth's path around the Sun, is the right size for scientific study, and is one of the oldest asteroids known to NASA. This asteroid represents a threat to our planet, because in a hundred years will approach the Earth at a very unsafe distance, according to the with reference to TSN.

Scientists estimate there is a one-in-2,700 chance of the asteroid slamming catastrophically into Earth 166 years from now.

Bennu is relatively close to Earth, and its orbit even crosses that of our planet, making a close approach every six years. Its proximity to us made it a prime target for OSIRIS-REx.

The mission will give vital information on how to deflect asteroids from their collision course with Earth. This mission, which will bring grains back for us to study on Earth, is the latest to return asteroid samples to Earth after the Japanese Space Agency's missions Hayabusa 1 and 2 and StarDust.

Asteroids may have played a role in the origins of life here on Earth by delivering organic molecules to our planet in its early days. Its composition is of particular interest as we already know it is rich in carbon.

There are a host of other reasons that NASA chose Bennu, and you can read about them all here. Osiris is the god of the afterlife, while Bennu represents the heron and creation. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. It orbits the sun at roughly the same distance as Earth.

"Today has been very exciting, but the true nail-biting moment will be the sample collection".

OSIRIS-REx and its instruments.

The spacecraft will also carry a laser altimeter, a suite of cameras provided by the University of Arizona, spectrometers and lidar, which is similar to radar, using light instead of radio waves to measure distance.

It also is equipped with a "touch-and-go-sample acquisition mechanism", or TAGSAM, on the end of a 10-foot-long robot arm. At its closest approach, only 4 miles (7 kilometers) will separate the ship from the surface. "We'll do this first globally, and from there prioritize two candidate sample sites".

The sampling arm will contact the surface of Bennu for five seconds. When the spacecraft is touching down, nitrogen gas from a canister will be released to make dust and pebbles rise and enter the sampler.

The sample container will then break free from Osirus Rex and head towards Earth in 2021, parachuting down to Utah.

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