Hayabusa returns first asteroid sample to Earth

Just before midnight local time on 13 June 2010, the sky over the Woomera Prohibited Area in South Australia tore open. A brilliant fireball fragmented into glowing shards as the Hayabusa mothership, which had no heat shield and was never meant to survive, burned up beside the small capsule it had released hours earlier. The 40-centimetre capsule streaked ahead of the debris, deployed its parachute, and settled onto the red outback soil. Inside were a few thousand microscopic grains of asteroid, the first ever brought home, ending a seven-year, roughly six-billion-kilometre odyssey that had nearly failed a dozen times.

Hayabusa had launched on 9 May 2003 aboard an M-V rocket and reached the 535-metre asteroid Itokawa on 12 September 2005, propelled by experimental microwave-discharge ion engines. That November it descended twice to the rubble-pile surface. The sampling system, a gun designed to fire pellets into the regolith and blast fragments into a collection horn, almost certainly never fired. During the first attempt the spacecraft unexpectedly settled onto the asteroid and sat there for about half an hour, becoming the first craft ever to land on an asteroid and take off again. Dust kicked up during the touchdowns drifted into the horn anyway.

Then came the ordeal. A fuel leak in December 2005 sent the spacecraft tumbling, and ground stations lost it entirely for seven weeks. Reaction wheels failed. Batteries degraded. The return slipped three years. In November 2009, with two of four ion engines dead and two half-broken, engineers executed one of spaceflight's great improvisations: they wired the working neutralizer of thruster A to the working ion source of thruster B, creating a single virtual engine from two corpses, and it carried Hayabusa home.

Recovery teams retrieved the capsule the next day. In November 2010, JAXA announced that about 1,500 rocky grains inside, most smaller than a tenth of a millimetre, were confirmed material from Itokawa. The grains tied S-type asteroids directly to the ordinary chondrite meteorites in museum drawers, and the mission's against-all-odds homecoming made Hayabusa a national hero in Japan, inspiring feature films and its more ambitious successor, Hayabusa2.