BioEd Online

The first results from a smashed spacecraft's cargo are proving that useful science can be salvaged from the wreckage.

The Genesis probe spent more than two years sampling the solar wind, the stream of particles coming from the Sun, by trapping the particles in wafers of diamond, silicon and other materials.

But when the probe returned to Earth in September 2004, its parachute failed to open. It slammed into the Utah desert at more than 300 kilometres per hour, exposing its cargo to Earth's atmosphere.

Luckily, the tiles were contaminated only on their surface, so atoms buried a few hundred nanometres deep should be from the Sun, not Utah.

"The most important result is that we've managed to pull something out of this," says Don Burnett, a geochemist from the California Institute of Technology in Pasadena, who leads the mission's science team. His team presented its work at the Lunar and Planetary Science Conference in League City, Texas, on 14 March.

The answer, my friend...

Like the Stardust mission to sample a comet's tail (see ' Comet chasers get mineral shock'), Genesis was designed to investigate the birth of our Solar System. The solar wind, which contains material from the Sun's outermost layer, is more than 90% hydrogen, plus some helium and traces of other elements. This is thought to resemble the cloud of gas and dust from which the planets formed some 4.6 billion years ago.

Studying the trace elements in the wind, particularly oxygen, could help scientists to distinguish between different theories of how the Solar System began. Oxygen atoms come in different masses, and rocks from the Earth, Moon and meteorites contain differing ratios of these isotopes.

This suggests that something must have separated the light and heavy atoms in the protoplanetary soup. Comparing isotope ratios in rocks with the ratio in the Sun might show what this was. It could also answer questions such as how brightly the young Sun shone.

"The trouble is, we have no idea what the oxygen isotope ratio of the Sun is," says Burnett.

...is blowin' in the wind

The scientists first had to be sure that the particles in the solar wind give a true picture of the Sun's surface. The wind's chemical composition depends on its speed, which varies from 250 to 800 kilometres per second. Does the ratio of different isotopes of the same elements vary in the same way?

Apparently not, according to research presented by Charles Hohenberg of Washington University in St. Louis, Missouri. His team has salvaged and analysed data on the different neon isotopes in the wind. The relative proportions of neon did not depend on the wind's speed, suggesting that the same will be true for oxygen.

So if the team can extract oxygen from the samples, the isotope ratios should indicate that in the Sun itself.

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