The Hayabusa2 spacecraft left the asteroid Ryugu, about 300 million km (180 million miles) from Earth, a year ago and is expected to reach Earth and drop a capsule containing the precious samples in southern Australia on 6 December. 

Scientists at the Japan Aerospace Exploration Agency (Jaxa) believe the samples, especially those taken from under the asteroid’s surface, contain valuable data unaffected by space radiation and other environmental factors.

Makoto Yoshikawa, a Hayabusa2 project mission manager, said scientists are especially interested in analysing organic materials in the Ryugu soil samples. “We are hoping to find clues to the origin of life on Earth by analysing details of the organic materials brought back by Hayabusa2,” he explained. 

Jaxa plans to drop the capsule containing the samples on to a remote, sparsely populated area in Australia from 220,000km (136,700 miles) away in space. They said this is a big challenge requiring precision control.

The team said the capsule, protected by a heat shield, will turn into a fireball during re-entry in the atmosphere at 200km (125 miles) above ground. Then at around 10km (six miles) above ground, a parachute will open to prepare for landing, and beacon signals will be transmitted to indicate its location.

Jaxa staff have set up satellite dishes at several locations in the target area to catch the signals, while also preparing marine radar, drones and helicopters to assist in the search and retrieval mission. Dr Yoshikawa said that without those measures, a search for the pan-shaped capsule with a diameter of 40cm (15in) would be an “extremely difficult” task.

The team added that it is not the end of the Hayabusa2 mission that it started back in 2014. After dropping the capsule, it will return to space and head to another distant small asteroid called 1998KY26 – a journey slated to take around 10 years.

Hayabusa2 touched down on Ryugu twice, despite its extremely rocky surface, and successfully collected data and samples during the one-and-a-half years after it arrived there in June 2018.

In its first touchdown on the asteroid in February 2019, it collected surface dust samples. And in July, it collected underground samples from the asteroid for the first time in space history after landing in a crater that it had earlier created by blasting the asteroid’s surface.

Scientists have said there are traces of carbon and organic matter in the asteroid soil samples, and Jaxa hopes to find clues to how the materials are distributed in the solar system and are related to life on Earth.

Asteroids, which orbit the Sun but are much smaller than planets, are among the oldest objects in the solar system and therefore may help explain how Earth evolved.

It took the spacecraft three-and-a-half years to arrive at Ryugu – which in Japanese means 'Dragon Palace', the name of an undersea castle in a Japanese folktale – but the journey home was much shorter because of the current locations of Ryugu and Earth.