Sometime late this month a robotic deep-space probe will begin gathering up bits of the sun--specifically, the solar wind. Twenty-nine months afterward NASA's Genesis spacecraft will begin the long trip back home bearing a precious hoard of pristine solar-wind samples weighing no more than a few grains of salt. On arrival in Earth's atmosphere in April 2004, the spacecraft's 210-kilogram return capsule and its fragile cargo will ride the winds on a special high-lift parachute to a dramatic midair capture by helicopter over the Utah desert. The specimens will be the first extraterrestrial material collected from beyond the orbit of the moon.

Solar wind consists of invisible charged particles ejected from the sun's surface at high velocities. Whereas the sun's interior has been modified by nuclear reactions, the outer layers are thought to be composed of the same material as the original solar nebula, the cloud of interstellar gas and dust that gave rise to the solar system some 4.6 billion years ago. Prospecting the sun's surface is impossible, so the next best thing is to collect material flung out from its hot, turbulent exterior.

This article was originally published with the title Catching Some Sun.

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