Three years late, Japanese asteroid dust probe returns

Kathy Marks@kathymarksoz
Sunday 23 October 2011 07:13

Considering the problems that have plagued the Japanese space probe Hayabusa during its seven-year, 2.5 billion-mile unmanned mission, it was remarkable that it returned home at all, never mind in quite so spectacular a fashion.

Early yesterday a fireball lit up the night sky over the Australian Outback as Hayabusa burned up on re-entering Earth's atmosphere, releasing a capsule which landed in the desert.

International scientists gathered in the remote spot in southern Australia were waiting for dawn before retrieving the heat-proof device, which they hope contains dust that will help unlock some of the solar system's secrets. "It was like a shooting star with a starburst behind it. It was fantastic," one defence official told Reuters.

Launched by the Japan Aerospace Exploration Agency in 2003, the spacecraft had the mission of collecting samples from an ancient asteroid, Itokawa, about a billion miles away, beyond Mars. It landed there in 2005, but a litany of problems delayed its return by three years.

The probe's sampling collection device failed, but scientists believe it must have picked up microscopic grains of dust while landing on Itokawa. Even one grain can be "sliced into more than 100 pieces and farmed around the world for testing and research", according to Michael Zolensky, one of two Nasa scientists involved in the project.

Researchers hope to study how and when the asteroid was formed, its physical properties, and what other celestial bodies it may have been in contact with. The aim is to gain fresh insight into the origin and evolution of the solar system, and also to reduce the threat of an asteroid colliding with Earth.

During the $200m (£137m) mission, Hayabusa – which means "falcon" in Japanese – suffered fuel leaks, engine problems and malfunctioning of its stabilising wheels and electricity-storing batteries. The car-sized probe also lost communication for seven weeks. Some dubbed it the "robotic equivalent of Apollo 13", which was beset by technical problems but managed to limp home after aborting a lunar landing.

Stretches of South Australia's main north-south highway, as well its transcontinental train line, were closed in anticipation of the capsule's landing in the Woomera rocket test range, a military zone. Yesterday morning, Aboriginal elders were planning to accompany scientists retrieving the capsule – before it is flown to Japan – to make sure it had not damaged any sacred sites.

The first spacecraft to complete a round-trip journey to an asteroid, Hayabusa is only the fourth to bring home space material. Samples were collected on the Moon; during Nasa's Genesis mission in 2004, which picked up particles of solar wind; and during the 2006 Stardust mission, which returned with samples of a comet.

Trevor Ireland, a geochemist at the Australian National University and a member of the team, said: "There's absolutely nothing like going to the source. Hayabusa has sampled an asteroid in situ and soon we will have in hand an actual asteroid. Any sample coming back from Itokawa will be a major scientific prize for us."

Dr Zolensky said even one grain could shed light on the asteroid's chemical and mineralogical characteristics. "You can do incredible things with a sample that small." On the question of an asteroid colliding with Earth, he said: "If you want to mitigate that hazard, you have to know about the physical properties of asteroids."

As well as bringing dust home from Itokawa, the probe left a souvenir of Earth on the asteroid: an aluminum plate bearing the names of 880,000 people from 149 countries, including the US film-maker Steven Spielberg and the British science fiction writer Arthur C Clarke.

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