Earth’s water originated close to home, lava analysis suggests | Science News

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Earth’s water originated close to home, lava analysis suggests

Deuterium levels in mantle argue against comets as H2O source

2:00pm, November 12, 2015

WATERY WORLD  Water molecules embedded inside lava spewed by volcanoes in Iceland (like the one shown) and Canada suggest that Earth’s H2O originated from water-laden dust.

Molecules entombed inside pristine magmas suggest that Earth’s water came from soggy dust, not icy comets.

The relative abundance of a heavier variety of hydrogen called deuterium serves as a fingerprint of where in the solar system a reservoir of H2O originated (SN: 5/16/15, p. 18). Previous work hunting for the source of Earth’s water measured deuterium in seawater, but that’s a tainted metric, researchers report in the Nov. 13 Science. Aboveground processes such as hydrogen atoms leaking into space can hike deuterium concentrations in the planet’s surface water (SN: 9/5/15, p. 8).

The researchers found that deuterium levels in water trapped inside molten rock unaltered since the planet’s early days are

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