Mystery: Where Did Earth's Water Come From?

Astronomers probing the mystery of where the Earth's water came from have eliminated a leading hypothesis: that water came to Earth as a result of a comet.

"Over the past few months, the European Space Agency's Rosetta space probe closely examined the type of comet that some scientists theorized could have brought water to our planet 4 billion years ago. It found water, but the wrong kind," CBC News reported.

"Europe's Rosetta mission....made history by landing on Comet 67P in November," the BBC reported.

The findings conclude that the water on the comet was too heavy to fit the parameters of Earth. It was comprised of more deuterium, a hydrogen isotope, than Earth's water, according to the CBC report.

"It is more than three times higher than on the Earth, which means that this kind of comet could not have brought water to the Earth," according to Kathrin Altwegg of the University of Bern, a lead researcher on the project.

"We have light water in some comets and very heavy water in other comets. We have to assume the mixture of all these comets is something that is heavier than what we have on Earth, so this probably rules out [this particular belt of] comets as the source of terrestrial water," she said, per the BBC.

Altwegg recently published the findings in the journal Science. The journal article explained that the source of the planet's water is a mystery in the scientific community. "The provenance of water and organic compounds on the Earth and other terrestrial planets has been discussed for a long time without reaching a consensus," the study said.

Altwegg explained how the community views this issue. "The question is who brought this water: Was it comets or was it something else?" she said, per the CBC report. Now Altwegg believes asteroids may have brought the water, the report said.

Image credit: "Comet C/2011 L4 PANSTARRS over Upper Ferntree Gully, Victoria, Australia," Chris Samuel © 2013, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/

http://www.wateronline.com/doc/mystery-where-did-earth-s-water-come-from-0001