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Space.com: The meteorites that brought water to Earth must have done so fairly early in the planet’s formation. Yuki Kimura of Tohoku University and colleagues used transmission electron microscopy to study fragments from the Tagish Lake meteorite, which fell to Earth in 2000. Colloidal crystals in the meteorite were found to be composed of magnetite nanoparticles that crystallized as water in the parent asteroid sublimated, or passed directly from a solid to a gas. The fact that that would have occurred fairly early in the solar system’s formation is backed up by an earlier study, in which it was found that water probably already existed on Earth when the Moon was formed from debris resulting from a collision between our planet and another object of similar size.
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Early asteroid likely water source for Earth Free
28 October 2013