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Abu Dhabi, UAETuesday 11 December 2018

Nasa spacecraft arrives at ancient asteroid after two-billion kilometre chase

Robotic explorer Osiris-Rex comes within 19km of diamond-shaped space rock named Bennu

Osiris-Rex made it to Bennu - exactly one week after Nasa landed a spacecraft on Mars. Nasa
Osiris-Rex made it to Bennu - exactly one week after Nasa landed a spacecraft on Mars. Nasa

After a two-year chase, a Nasa spacecraft arrived on Monday at the asteroid Bennu, its first visitor in billions of years.

Osiris-Rex pulled within 19 kilometres of the 500-metre, diamond-shaped space rock but will get even closer in the days ahead and go into orbit around Bennu on December 31. No spacecraft has ever orbited such a small cosmic body.

It is the first US attempt to gather asteroid samples for return to Earth, something only Japan has accomplished so far.

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Flight controllers applauded and exchanged high-fives when confirmation came through that Osiris-Rex made it to Bennu – exactly one week after Nasa landed a spacecraft on Mars.

“Relieved, proud, and anxious to start exploring!” tweeted lead scientist Dante Lauretta of the University of Arizona. “To Bennu and back!”

With Bennu currently 122 million kilometres from Earth, it took seven minutes for word to get from the spacecraft to flight controllers at Lockheed Martin in Littleton, Colorado where the probe was built.

About the size of a large car, the spacecraft will shadow the asteroid for a year before scooping up some gravel for return to Earth in 2023.

Scientists are eager to study material from a carbon-rich asteroid like Bennu, which could hold evidence dating back to the beginning of our solar system 4.5 billion years ago. As such, it’s an astronomical time capsule.

A Japanese spacecraft has been hanging out at another near-Earth asteroid called Ryugu since June. Japan’s second asteroid mission will bring samples back to Earth by December 2020 but less than Osiris-Rex’s promised booty.

The US probe aims to collect at least 60 grams of dust and gravel. The spacecraft will not land on Bennu, but will use a three-metre mechanical arm to momentarily touch down and vacuum up particles. The sample container will break loose and head back to Earth.

The collection – parachuting down to Utah – would represent the biggest cosmic haul since the Apollo astronauts hand-delivered moon rocks to Earth in the late 1960s and early 1970s.

Nasa brought back comet dust and solar wind particles before, but never asteroid samples. Japan managed to return some tiny particles in 2010 from its first asteroid mission, named Hayabusa.

Both Bennu and Ryugu are considered potentially hazardous asteroids. That means they could smack into Earth years from now. At worst, Bennu would carve out a crater during a projected close call 150 years from now.

Contact with Bennu will not significantly change its orbit or make it more dangerous to us, Lauretta stressed.

Scientists say the more they learn about asteroids, the better equipped Earth will be in heading off a catastrophic strike.

The $800 million (Dh3 billion) Osiris-Rex mission began with a 2016 launch from Cape Canaveral, Florida. It has put nearly two billion kilometres on the clock as of Monday.

Both the spacecraft and asteroid’s names come from Egyptian mythology. Osiris is the god of the afterlife, while Bennu represents the heron and creation.

Osiris-Rex is actually a Nasa acronym for "origins, spectral interpretation, resource identification, security-regolith explorer".