Ancient volcanic rocks may have preserved tiny samples of the planet’s original moisture.
Liquid water covers some 70 percent of Earth’s surface, making the planet unique in the solar system. But where that water came from has been a bit of a puzzle.
Early in its history, Earth’s surface was so hot that any water would have evaporated into space. Anything that is here today, scientists have thought, must have come from asteroids or comets that later struck the cooling world.
But maybe not. A new analysis in Science suggests that at least some of Earth’s current moisture derives from water-soaked dust particles trapped deep inside during the planet’s formation.
To figure out where Earth’s water came from, scientists look at the ratio of deuterium to hydrogen found in the H2O molecules. Deuterium is an isotope of hydrogen that contains a proton and a neutron in its core, while an atom of hydrogen has only the proton. Read more
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