Spacecraft reaches ancient asteroid that could hit Earth

CAPE CANAVERAL: After a twoyear chase, a Nasa spacecraft has arrived at the ancient asteroid Bennu, its first visitor in billions of years.

The robotic explorer OsirisRex, right on cue, pulled within 19km of the diamondshaped space rock yesterday.

It will get even closer in the days ahead and actually go into orbit around Bennu on December 31. No spacecraft has ever orbited such a small cosmic body.

Flight controllers applauded and exchanged highfives once confirmation came through — 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.

With Bennu more than 130 million kilometres away, it took seven minutes for word to get from the spacecraft to flight controllers at Lockheed Martin in Littleton, Colorado, where the spacecraft was built.

Bennu is estimated to be just a little more than 500m across.

Researchers will provide a more precise description at a scientific meeting early next week in Washington.

About the size of an SUV, 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 carbonrich asteroid such as dark Bennu, which could hold evidence dating back to the beginning of our solar system 4.5 billion years ago.

A Japanese spacecraft, meanwhile, has been hanging out at another nearearth asteroid since June, also for samples. It is Japan’s second asteroid mission.

This latest rock is named

Ryugu and about double the size of Bennu.

Ryugu’s specks should be here by December 2020, but will be far less than OsirisRex’s promised booty.

OsirisRex aims to collect at least 60gm of dust and gravel from Bennu.

The spacecraft will not land, but will use a 3m mechanical arm in 2020 to vacuum up particles. The sample container will break loose and head towards Earth in 2021.

The collection — parachuting

down to Utah — will represent the biggest cosmic haul since the Apollo astronauts handdelivered moon rocks to earth in the late 1960s and early 1970s.

Both Bennu and Ryugu are considered potentially hazardous asteroids. That means they could smack Earth years from now.

At worst, Bennu could carve out a crater during a projected close call 150 years from now.

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