Next time you're swimming in the ocean, consider this: part of the water is older than the sun.
So concludes a team of scientists who ran computer models comparing the ratios of hydrogen isotopes over time. Taking into account new insights that the solar nebula had less ionizing radiation than previously thought, the models show that at least some of the water found in the ocean, as well as in comets, meteorites and on the moon, predate the sun's birth.
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The only other option, the scientists conclude, is that it formed in the cold, intersteller cloud from which the sun itself originated.
The discovery, reported in this week's Science, stems from the insight of lead author Lauren Ilsedore Cleeves, a doctoral student at the University of Michigan, who realized that planet-forming disks around young stars should be shielded from galactic rays by the strong solar winds, dramatically altering the chemistry occurring inside the disks, said Conel Alexander, with the Carnegie Institution of Washington.