New research suggests water appeared on Earth much earlier than we thought it did.
The Earth is covered by more than 70 percent water, and researchers have long wondered when we first became the "blue planet," the Woods Hole Oceanographic Institution reported.
"The answer to one of the basic questions is that our oceans were always here. We didn't get them from a late process, as was previously thought," said Adam Sarafian, the lead author of the paper published Oct. 31, 2014, in the journal Science and a MIT/WHOI Joint Program student in the Geology and Geophysics Department.
In the past researchers have hypothesized that water came to Earth later on in its development. Some have wondered if the planets were formed dry, and received water from "wet" asteroids.
"With giant asteroids and meteors colliding, there's a lot of destruction," said Horst Marschall, a geologist at WHOI and coauthor of the paper. "Some people have argued that any water molecules that were present as the planets were forming would have evaporated or been blown off into space, and that surface water as it exists on our planet today, must have come much, much later-hundreds of millions of years later."
The researchers looked at carbonaceous chondrites, which were primitive meteorites and formed from the same debris as the sun. They contain a significant amount of water. In order to measure the water in these bodies the scientists looked at the ratio between the two stable isotopes of hydrogen: deuterium and hydrogen.
The team looked at samples of the asteroid 4-Vesta, which is believed to have formed in the same region of the solar system as Earth and has a surface composed of basaltic rock (frozen lava). They found 40Vesta contains the same hydrogen isotopic compositions as carbonaceous chondrites and Earth. The findings suggest these carbonaceous chondrites are the most likely source of Earth's water.The asteroid is beleived to date back to 14 million years after the solar system formed.
"An implication of that is that life on our planet could have started to begin very early," said WHOI geologist and coauthor Sune Nielsen. "Knowing that water came early to the inner solar system also means that the other inner planets could have been wet early and evolved life before they became the harsh environments they are today."
