Tokyo (AFP)

A Japanese probe dropped on Earth precious samples taken from a distant asteroid, which could inform us about the birth of our universe.

The refrigerator-sized Hayabusa-2 probe was launched in December 2014.

It deposited a hundred milligrams of particles from the asteroid Ryugu, "the dragon's palace" in Japanese, located some 300 million kilometers from Earth.

Scientists hope they will provide clues to the solar system when it was born 4.6 billion years ago.

The composition of large celestial bodies like the Earth changes drastically after their formation, under the effect of temperature and pressure.

Not that of the much smaller asteroids, mission leader Makoto Yoshikawa told reporters.

"We can therefore think that substances dating back 4.6 billion years are still there."

The possible presence of organic material, he adds, could tell us how life came to be on Earth.

The capsule containing the samples entered Earth's atmosphere shortly before 2:30 a.m. Sunday morning Japanese time (5:30 p.m. GMT Saturday), creating a fireball similar to the track of a shooting star.

It had separated from the probe itself on Saturday, when Hayabusa-2 was 220,000 kilometers from Earth.

"She's finally back after six years," a commentator for the Japanese Space Agency (JAXA) said as officials from the agency on live video loudly expressed their joy.

Protected from sunlight and radiation inside the capsule, the samples will be collected, processed in Australia and then sent by air to Japan.

During its mission, the probe collected last year from the asteroid both surface dust and substances obtained by drilling.

Half of the material collected will be shared between Jaxa, NASA and international organizations, and the remainder will be kept for future studies, as analytical technology advances.

- Ten more years -

After this express delivery, the work of the probe is not finished: scientists from the Japanese space agency plan to extend its mission by more than ten years by targeting two new asteroids.

Hayabusa-2 will first perform a series of orbits around the sun for about six years to record data on dust in interplanetary space and observe exoplanets.

The probe will then approach its first target in July 2026. While remaining at a certain distance from the asteroid 2001 CC21, scientists nevertheless hope that it will be able to photograph it "while passing at high speed".

Hayabusa-2 will then head towards its main target, 1998 KY26, a spherical asteroid with a diameter of only 30 meters.

When the probe reaches it in July 2031, it will be about 300 million kilometers from Earth.

The extension of its mission involves risks, in particular that of seeing the probe's equipment deteriorate in deep space.

© 2020 AFP