A Japanese spacecraft is approaching the surface of an asteroid about 280 million kilometres (170 million miles) from Earth. The Japan Aerospace Exploration Agency said Thursday that Hayabusa2 began its approach at 1:15 p.m.
The start was delayed for about five hours for a safety check, but the unmanned craft is still is due to touch down as scheduled on Friday morning.
It will attempt to collect material from the asteroid that could provide clues about the origin of the solar system and life on Earth. After a successful landing, the craft will shoot a 5-gram bullet made from the element tantalum into a pile of gravel in a vacuum chamber at 300 meters per second into the rock in order to capture samples to bring back to Earth.
The bullet would break up and release enough material of the right size for Hayabusa2 to gather samples.
Japanese scientists expected to find a “powdery regolith” on the asteroid, according to the release. But when the MASCOT and MINERVA-II1 rovers dropped by Hayabusa2 prowled the surface, they found that it was actually covered in centimetre-sized gravel bits. The team delayed the probe’s touchdown in order to ensure that their collection mechanism would still work on the larger grit.
Hayabusa2 launched in 2014 to rendezvous with and collect samples form the asteroid Ryugu. It succeeds the troubled, but ultimately successful Hayabusa mission, and joins NASA’s OSIRIS-REx as one of two missions currently exploring asteroids up-close.
If successful, Hayabusa2 will take three samples from Ryugu’s surface and return them in a capsule to Earth in December 2020.
The asteroid is about 900 meters (3,000 feet) in diameter. It is named Ryugu after an undersea palace in a Japanese folktale.