Discovery hints at Earth's water source

LEIDEN, Netherlands, Oct. 21 (UPI) -- European astronomers say they've found a very cold reservoir of water vapor in space that could explain where the Earth's water came from.

Scientists have long debated how the Earth, far too hot to hold water or water vapor in its early history, came to have oceans relatively quickly in geological time.

Now astronomers at the Leiden Observatory in the Netherlands say they've they discovered a cold water vapor zone at the outer reaches of a dusty disk surrounding a star 175 light-years away, The Washington Post reported Thursday.

The star and disk are in the early stages of forming planets much as Earth was formed around the sun some 4.5 billion years ago, the astronomers say.

They say they believe water was almost certainly delivered to Earth via comets and asteroids known to originate in these cold but water-filled zones, assumed to also be present when our solar system was forming.

"Scientists have long suspected there were these reservoirs of cold water vapor hiding in the outer regions of planet-forming disks," Leiden astronomer Michiel Hogerheijde said.

"Our observations of this cold vapor indicate enough water exists in the disk to fill thousands of Earth oceans," he said.