NASA gives go-ahead for unmanned spacecraft to hit asteroid

Image copyright AFP/Getty Images Image caption The space agency believes that another huge impact could spark a larger one

A NASA spacecraft has been given permission to hit an asteroid in a remote spot to see how its impact could stunt a potential impact – an exercise that could help protect Earth.

After being advised by astronomers of the asteroid’s path, the agency decided the craft could be useful in testing its planetary defence system.

The spacecraft, called the Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer (OSIRIS-REx), is currently on its way to a relatively wide-open space – known as “perijove”.

The asteroid (which won’t actually hit us, NASA officials stress) will actually be a near-Earth object, so our planet will not be hit by it.

ASAT is a typical Earth flyby mission, so the craft will fly within 1.5 million kilometres of the ground.

Its manoeuvring is merely “showing” what is going to happen to the asteroid if it hits, in a direction and speed not controlled by the craft’s computer.

Image copyright NASA Image caption The spacecraft is equipped with cameras and radar that allow it to reveal the texture of an asteroid surface

OSIRIS-REx will continue to slowly fly by the asteroid until mid-February 2022, when it will hit it in what is known as an “astronomical close approach”.

The spacecraft will plough into the surface of an asteroid 20m across. A significant impact would provide the boost the spacecraft needs to make the full journey to the asteroid itself.

About a year later, in mid-December 2024, it will attempt to touch down on the surface of a second asteroid called Bennu.

Bennu is nearer, at 25m across, but the spacecraft may still need to fire its powerful heat shield in order to make it past the asteroid’s other side to its home side – and then it will need to gather as much new data as possible before moving on.

‘We are losing the asteroid race’

Fortunately, Bennu does not threaten us.

The craft has the power to hit the asteroid multiple times, meaning the asteroid could survive it each time, until it is eventually crushed up, or sterilised, into a miniscule dust ball in a matter of months.

It may just be a test to see how well all this technology works, or it could be a precursor to a bigger hit in the future.

“We’ve got to practice what we might be doing if it should happen. We’re probably losing the asteroid race because we don’t know where to hit,” said Mike Benton, a planetary defence expert at the Planetary Science Institute in Tucson, Arizona.

NASA projects that, without its mission, it could be another 1,000 years before another one of these near-Earth objects makes a pass by the Earth.

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