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Sunday, Nov. 21, 2010

EDITORIAL

Particles from an asteroid

The Japan Aerospace Exploration Agency (JAXA) announced Nov. 16 that it has determined that most of some 1,500 particles contained in the unmanned space probe Hayabusa (peregrine falcon), which returned to Earth in June from the asteroid Itokawa, originated from the asteroid orbiting Earth and Mars.

Hayabusa, launched in may 2003, landed on the 550-meter-long asteroid twice in November 2005. Although it failed to collect rocks and sand from Itokawa, it was hoped that dust kicked up by the probe's landing had entered the capsule. Hayabusa returned to Earth after a seven-year, 6-billion-km trip, overcoming a series of troubles, including engine and communication problems.

This is the first time that mineral samples from an asteroid have been collected. Minerals from the Moon and comet dust had been the only extraterrestrial minerals obtained. Japan can be proud of the feat achieved by Hayabusa and its mission team.

Most of the particles measure one-1,000th to one-100th of a millimeter. Their main components are olivine, pyroxene and plagioclase. Electronic microscope analyses have shown that the minerals found in Hayabusa contain more of the element iron than similar mineral samples from Earth, whose iron component ratio is low relative to magnesium. This characteristic matches that of rocks on the surface of Itokawa closely observed by Hayabusa from a short distance.

It is hoped that further study of the minerals from Itokawa will shed light on the origin of the solar system, which formed some 4.6 billion years ago. More particles from Itokawa may be found in other sections of Hayabusa. Since an asteroid does not have volcanoes or magma, its rocks are believed to have retained characteristics that prevailed when the solar system formed.

Hayabusa's cost was relatively cheap at ¥12.7 billion. The government should push a project to launch an unmanned probe that succeeds Hayabusa. Meanwhile, it should rethink Japan's participation in the International Space Station project, which costs Japan ¥40 billion a year but whose scientific achievements do not appear to justify the cost.



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