Spacecraft in risky descent to asteroid 200 million miles from Earth

Late on Tuesday, 200 million miles away from planet Earth, a NASA spacecraft began a precarious descent to an asteroid.

The Osiris-Rex craft is attempting to collect a handful of rubble, which scientists say contains the building blocks of our solar system.

It dropped out of orbit around the asteroid, named Bennu, beginning a four and half hour descent to the boulder-covered surface of the space rock.

This is the USA’s first attempt to gather samples from an asteroid, something Japan has accomplished twice.

Osiris-Rex won’t be landing on the asteroid – as long as everything goes to plan – as Bennu’s gravity is too low, being just 510 metres across.

Instead, the spacecraft will reach out with a robotic arm, to try to collect between 60 grams and 2 kilograms of material.

“We’ll only be kissing the surface with a short touch-and-go measured in just seconds,” said the University of Arizona’s Heather Enos, the deputy scientist for the mission.

After nearly two years orbiting Bennu, the spacecraft found this location to have the biggest patch of particles small enough to be swallowed up.

By the time flight controllers near Denver hear back from Osiris-Rex, the action already will have happened 18 and a half minutes earlier – the time it takes radio signals to travel each way between Bennu and Earth.

NASA won’t know until later this week how much was actually collected — or whether the spacecraft got anything at all.

The $800-plus million mission started with a launch back in 2016, and the spacecraft isn’t expected back on Earth until 2023.