An artist's illustration of Hayabusa2 returning to Earth. Image ©Akihiro Ikeshita.

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Hayabusa2 returns precious asteroid samples to Earth after six-year mission

The spacecraft Hayabusa2 is arriving back to Earth after six years' travel through the solar system.

It is carrying fragments of rock collected from the surface of asteroid Ryugu. Studying these samples will reveal more about what asteroids are made from and how they formed in the early solar system, which is an important step to understanding how planets like the Earth formed.

The mission has been operated by the Japan Aerospace Exploration Agency (JAXA).

Scientists at the Museum have been monitoring the Hayabusa2's progress since it left Earth in December 2014. They'll also be on the team examining the samples that Hayabusa2 has carefully transported home.

Dr Ashley King, a planetary scientist, says, 'This is such an exciting time. I was in Japan for the launch and watched it on a big screen with many of the scientists who will be analysing the samples.

'I'm really looking forward to comparing the Ryugu samples with the meteorites that we have been studying at the Museum.'

Ryugu is one of 18,000 near-Earth asteroids, which means its orbit could bring it close to Earth.

Measuring about one kilometre in diameter, the asteroid is not one solid mass, but rather space rubble that has been stuck together by gravity.

Finding out more about the composition of that rubble could be the key to unlocking knowledge about existing meteorite collections.

There are plenty of rocks in Museum collections and universities that have broken off from asteroids and entered Earth's atmosphere. Once a rock touches the Earth's surface after coming through the atmosphere, it is called a meteorite.

Scientists are studying these rocks to learn more about the solar system - but there is a lot that they still have left to understand.

Dr King explains, 'Ryugu is a dark asteroid that looks similar to some of the carbonaceous chondrite meteorites that we have in our collection. These meteorites are exciting because they contain large amounts of water and organic molecules and potentially delivered the ingredients for life to the Earth.

'Over the last few years we've been researching the carbonaceous chondrites but they have been exposed to the terrestrial environment, which can change the water and organic phases, and we don't know which asteroid they came from. This won't be an issue for the Ryugu samples so we'll be able to learn lots more about water and organics in the solar system.'

The landing

Hayabusa2 is expected to release a capsule containing its precious cargo once it reaches the skies high above South Australia. It will turn into a fireball when it re-enters the atmosphere, so it is protected by a heatshield.

Experts are on standby in South Australia to search for the 40cm capsule once its reaches the ground.

Samples will then be analysed by an international team.