The Japanese space probe arrives at the asteroid to collect samples

Asteroid Ryugu seen from a distance of about 25 miles. Photo: JAXA

A Japanese space probe arrived at an asteroid on Wednesday after a three-and-a-half-year trip to begin a first experiment: blowing up a crater in the rock surface to collect samples and bring them back to Earth.

The unmanned spacecraft Hayabusa2 has reached its base of operations about 20 kilometers (12 miles) from the asteroid and some 280 million kilometers (170 million miles) from Earth, announced the Japan Aerospace Exploration Agency.

Over the next year and a half, the robotic explorer will attempt three brief and quick landings to collect samples. If recovery and return are successful, the asteroid material could provide clues about the origin of the solar system and life on Earth.

The mission is difficult. Hayabusa2 will spend approximately two months searching for suitable landing sites on the uneven surface. Due to the high surface temperature, there will only be a few seconds each time it lands. All samples will be returned in a re-entry capsule that will arrive at the end of 2020.

The asteroid named Ryugu after an underwater palace in a Japanese folk tale, is about 900 meters in diameter. In the photos published by JAXA, the Japanese space agency, it appears more cube-shaped than round. A number of big craters can be seen, which project director Yuichi Tsuda said in an online article, making the selection of landing points "both interesting and challenging".

The first landing is scheduled for September or October. Prior to the last landing, scheduled in April or May, Hayabusa2 will send a stocky cylinder that explodes over the asteroid, firing a 2 kilogram (4.4 lb) copper projectile at high speed to form a crater. .

Hayabusa2 will hide from the other side of the asteroid to protect himself during the operation and will wait another two to three weeks to make sure any debris that could damage the explorer has faded away. It will then attempt to land at or near the crater to collect underground material that has been expelled from the crater, in addition to the surface material from the first landings.

The spacecraft will also deploy three rovers that have no wheels but that can jump on the surface of the asteroid to conduct probes. Hayabusa2 will also send a Franco-German undercarriage to study the surface with four observation devices.

Asteroids, which revolve around the sun but are much smaller than the planets, are among the oldest objects in the solar system. As such, they can help explain how the Earth has evolved, including ocean formation and the beginning of life.

Hayabusa2, launched in December 2014, succeeds the Hayabusa 2003-2010 mission, which collected samples of a different asteroid type and took three years longer than expected following a series of technical problems, including a fuel leak and a loss of contact for seven weeks.

NASA also has an ongoing asteroid mission. His Osiris-Rex spacecraft is expected to reach the asteroid Bennu later this year and return with samples in 2023.

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