Missourian
Diamond Member
From Sky and Telescope:
Genesis Finding: Earth Has a Problem
September 8, 2004, was supposed to be a day of triumph for solar-system exploration. That's when a sealed capsule from NASA's Genesis spacecraft returned to Earth with samples of the solar wind carefully collected in space.
But when a malfunction caused the capsule to plummet from the sky onto Utah's high desert, it initially seemed that both the craft and any hope of salvaging its results were shattered.
Luckily, many of the delicate collectors inside survived the plunge...
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...Finally, the results are in. At the 39th annual Lunar and Planetary Science Conference in Houston, Texas, Kevin McKeegan (University of California, Los Angeles) announced that the Sun has proportionately far more oxygen-16, relative to oxygen-17 and -18, than is present in terrestrial seawater. There's a serious mismatch. Instead, the solar ratios follow the same trend seen in primitive meteorites.
Suddenly, Earth is the odd planet out. "We had little idea what the Sun's ratios should be," McKeegan told me after his presentation. Now, he says, there's "no plausible model" to make Earth with the oxygen ratios it exhibits. "It's always been a challenge to supply Earth with the water it has. And now we're wondering how it got the rocks it has."
That view was echoed by Robert Clayton, a University of Chicago cosmochemist who's recognized as the grand master of oxygen-isotope research. "The CAIs [primitive meteorites particularly in tiny nuggets called calcium-aluminum inclusions] were thought to be the anomaly and we were normal," Clayton explained. "But this result has turned that idea upside down."
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