Earth's water may have come from materials that were present in the inner solar system at the time the planet formed, suggests a new study. The findings of this study, published in the journal Science, are surprising because the Earth's building blocks are often presumed to be dry.
"Our discovery shows that the Earth's building blocks might have significantly contributed to the Earth's water," said lead author Laurette Piani, a researcher at the Centre de Recherches Petrographiques et Geochimiques (CRPG, CNRS/Universite de Lorraine) in Nancy, France.
Essential Clues for Water On Matter
The researchers determined that a type of meteorite called an enstatite chondrite contains sufficient hydrogen to deliver at least three times the amount of water contained in the Earth's oceans, and probably much more.
Enstatite chondrites are entirely composed of material from the inner solar system -- essentially the same stuff that made up the Earth originally. "Hydrogen-bearing material was present in the inner solar system at the time of the rocky planet formation, even though the temperatures were too high for water to condense," Piani said.
The meteorites provide a clue that water did not have to come from far away comets or asteroids. "The most interesting part of the discovery for me is that enstatite chondrites, which were believed to be almost 'dry,' contain an unexpectedly high abundance of water," said Lionel Vacher, a postdoctoral researcher at Washington University in St. Louis.
Nitrogen and Hydrogen Isotopes
Vacher prepared some of the enstatite chondrites in this study for water analysis while he was completing his Ph.D. at Universite de Lorraine. Enstatite chondrites have similar oxygen, titanium and calcium isotopes as Earth, and this study showed that their hydrogen and nitrogen isotopes are similar to Earth's, too.
In the study of extraterrestrial materials, the abundances of an element's isotopes are used as a distinctive signature to identify where that element originated. "If enstatite chondrites were effectively the building blocks of our planet -- as strongly suggested by their similar isotopic compositions -- this result implies that these types of chondrites supplied enough water to Earth to explain the origin of Earth's water, which is amazing," Vacher said.