July 16, 2012

Meteorites Source Of Earth’s Water, New Study Suggests

Lee Rannals for - Your Universe Online

New research suggests that meteorites, and their parent asteroids, are most-likely the sources of Earth's water.

Scientists have believed that comets, or a primitive meteorite called carbonaceous chondrites, were the sources of earth Earth's volatile elements, including hydrogen, nitrogen, and carbon. Having an understanding of where these volatiles came from is crucial when determining the source of water and life on the planet.

New research led by Carnegie Institution for Science's Conel Alexander and published in the July 12th edition of Science Express shows carbonaceous chondrites likely did not form in the same regions of the Solar System as comets, because they have much lower deuterium content.

Objects that form farther out should have a higher deuterium content in their ice than objects that formed closer to the Sun. And, those that formed in the same regions should have similar hydrogen isotopic compositions as well.

By comparing the deuterium content of water in carbonaceous chondrites to the deuterium content of comets, researchers are able to tell if they formed in similar regions of the Solar System.

Some scientists believe that both comets and carbonaceous chondrites formed beyond the orbit of Jupiter, or even at the edges of our Solar System, before eventually bringing volatiles and organic material to Earth. In order for this to be true, ice found in comets and the remnants of ice preserved in carbonaceous chondrites in the form of hydrated silicates would have similar isotopic compositions.

The team suggests that carbonaceous chondrites formed instead in the asteroid belt that exists between the orbits of Mars and Jupiter. They also believe that most of the volatile elements on Earth arrives from a variety of chondrites, not from a comet.

"Our results provide important new constraints for the origin of volatiles in the inner Solar System, including the Earth," Alexander said in a press release. "And they have important implications for the current models of the formation and orbital evolution of the planets and smaller objects in our Solar System."

The team analyzed samples from 85 carbonaceous chondrites for their study, which was partially funded by NASA.

The results of the study directly contradict the two most-prominent models for how the Solar System developed its current architecture.


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