Asteroid on collision course with

Image copyright NASA Image caption Artist’s impression of one end of Bennu

A NASA spacecraft designed to crash into an asteroid and bring a chunk of it back to Earth for analysis is hurtling towards its target.

The Centaur probe is scheduled to come within 28m of the surface of asteroid Bennu at 20:27 GMT on Friday (21:27 BST on Wednesday) during a fiery fall.

Asteroid Bennu is likely to have a surface that is scorched and partly covered in boulders.

NASA says it has had to make changes to the orbit of the probe in order to launch it.

But the organisation says it should be able to pull off the most ambitious space mission of its lifetime.

Messages were relayed from the moment of the crash using the Deep Space Network antenna on Hawaii’s Mauna Kea.

Image copyright NASA Image caption The impact will be a bit longer than expected

Scientists on the ground in California are now analysing the “near-space” data gathered by the spacecraft, which is 13 days into its 22-month mission to Bennu.

The rocks around Bennu will quickly vaporise when the Centaur destroys them with its impact. The Centaur itself will end up burning up in Earth’s atmosphere and scattering small bits of debris on the planet.

Playful space rocks are a near-constant feature in the solar system. During the early Solar System days a handful of asteroids were part of a collection of bodies that orbited the Sun.

But over time the galaxy grew up and the Sun surrounded by an ever-widening ring of planets, gas and dust.

When the dust and debris finally breaks off an asteroid, it slams into the Sun as a shockwave and heats up. This process eventually cools it down and makes it a point source.

The Centaur mission is a giant leap in the understanding of the fate of these spiky space rocks.

Image copyright NASA Image caption The Centaur spacecraft is launched from Cape Canaveral, Florida

Centaur would have a difficult time getting into orbit around Bennu, much less sending it back to Earth.

Here’s why:

Centaur is like a tank that weighs about 240 tonnes. While other spacecraft fly in a straight line, Centaur has an oddly angled bow span that follows the path of Bennu’s gravitational pull.

Centaur would then have to fly in the opposite direction of Bennu. In a straight line, Bennu would circle in a circular orbit in the inner solar system.

If Centaur’s course steered it into a desired orbit, the spacecraft would enter the vicinity of a dying, rotating star.

But instead of being blasted into a dying star, the Centaur would hit Bennu.

This would cause a large explosion in the asteroid’s atmosphere. Centaur will plunge into Bennu and “fall to a final fiery death” – a nuclear detonation, scientists say.

The “blow” is slowed by the spacecraft’s heat shield – which absorbs the solar radiation – but not enough to stop its shockwave.

“We will make sure the spacecraft is healthy and in proper shape,” says Peter Theisinger, Centaur’s project manager.

“We will also be carefully managing Centaur’s time in orbit for the best possible impact site.”

A NASA team will then analyse the impact crater in order to extract any chemical materials, ice and rock.

The final chunks of Centaur will be burned in the tail end of Earth’s atmosphere to release debris that hit the planet at a slightly lower speed than the earlier impact.

Image copyright NASA Image caption Observations will help scientists learn more about the potential impact sites

The ashes will fall to Earth in pieces and scientists are hoping people on the ground will retrieve samples of the rock for study.

Humanity has known about Bennu for years. In September 1999, scientists noticed that Bennu was also identified in two earlier orbits by spacecraft that circled the Sun: the Deep Impact probe and the Deep Impact follow-up, Deep Impact 2.

These probes studied solar wind flows on the surface and collected tiny samples to analyse in laboratories.

Bennu was also discovered in 2004 by a way of measuring variations in the sun’s magnetic field. It’s the smallest asteroid on Nasa’s Near-Earth Object catalog.

However, Bennu is often described as “hot, dry” because its surface is blanketed in salt.

This results from what scientists call “sodium deposition”, a process known as sublimation.

Image copyright NASA Image caption This asteroid was found in 1998 and featured in the movie Armageddon

The Centaur probe was officially designated on 27 January when Nasa decided to name it after the fighter jet designed to wipe out Germany’s last plane at the Battle of Britain during World War II.

The craft was named after Centaur, a destroyer during the Second World War and a favourite

Leave a Comment