Some zircon crystals found in Western Australia were dated at 4.4 billion years old. They were dated by measuring uranium decay to lead.
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But some scientists pointed out a potential problem: Atoms of lead might move around inside the crystal. "And if that happens, in the places where it's concentrated, you will measure an older age than the true age," Valley explains.
So Valley's team recently tackled this issue with a powerful new instrument that can pluck out and identify individual atoms, to create a kind of map of their distribution inside the crystal. They found that lead atoms do move around, but only a tiny bit — not enough to affect their age calculations. This particular crystal that they analyzed, they say, is 4.374 billion years old, plus or minus 6 million years.
Sam Bowring, a geologist at the Massachusetts Institute of Technology, says it's pretty hard to argue with this new study, which appears this week in the journal Nature Geoscience.
So Valley's team recently tackled this issue with a powerful new instrument that can pluck out and identify individual atoms, to create a kind of map of their distribution inside the crystal. They found that lead atoms do move around, but only a tiny bit — not enough to affect their age calculations. This particular crystal that they analyzed, they say, is 4.374 billion years old, plus or minus 6 million years.
Sam Bowring, a geologist at the Massachusetts Institute of Technology, says it's pretty hard to argue with this new study, which appears this week in the journal Nature Geoscience.
