Aug. 28 (UPI) -- For decades, planetary scientists have been operating under the assumption that Earth was born dry, its water arriving only later, delivered via comets and asteroids.
But in a new study, published Friday in the journal Science, researchers argue Earth was always wet, formed by waterlogged building blocks. The proof: a collection of meteorites called enstatite chondrites.
"[Enstatite chondrites] are rocky meteorites made mostly of silicate, metal and sulfides," lead study author Laurette Piani told UPI in an email.
"They have a very peculiar mineralogy with phases such as calcium- or magnesium-sulfides, nitrides, and silicide that are almost nonexistent on Earth, although their isotope compositions of many elements indicate a clear link with the Earth building blocks," said Piani, a researcher at the University of Lorraine in France.
Because enstatite chondrites are delicate and reactive, they are easily transformed beyond recognition. Pristine enstatite chondrites, unmarred by collision, are especially rare. But most scientists agree that these rocks were the primary building blocks for early Earth.
"Chondrules are among the most abundant constituents of primitive meteorites and are among the first solids to form in the solar system," Piani.
Because enstatite chondrites formed in the inner solar system, so close to the sun's extreme heat, scientists have long assumed that these rocky meteorites were dry, totally devoid of hydrogen.
However, when Piani and her research partners surveyed enstatite chondrites using a pair of advanced imaging and isotopic analysis techniques, they not only found evidence that hydrogen is abundant in portions of the primitive rocks, but that their ratios of hydrogen and nitrogen isotopes are similar to those found on Earth.
"We found that a part of the hydrogen is present dissolved in the silicate glass of chondrules," Piani said. "Chondrules are among the most abundant constituents of primitive meteorites and are among the first solids to form in the solar system."
Their findings suggest Earth's building blocks were the opposite of dry.
"We propose in the paper that the water present in the Earth's mantle was directly inherited from enstatite chondrite-like material and present from the beginning of the Earth formation, while the surficial water, or oceans, could be made out of about 95 percent of EC-like material and 5 percent of hydrated asteroids."
In follow-up studies, researchers hope to figure out how enstatite chondrites came to host so many volatile elements.