European Space Agency scientists say our planet's seas and oceans formed from water carried to Earth by asteroids

Dec 11, 2014 08:22 GMT  ·  By

In a new paper published in yesterday's issue of the journal Science, researchers with the European Space Agency argue that our planet's seas and oceans most likely formed from water carried to Earth not by comets, but by asteroids.

The scientist base this claim on data indicating that the water included in the makeup of Comet 67P/Churyumov-Gerasimenko, which the Rosetta spacecraft has been orbiting since this year's August, is quite different to the water found on our planet.

The presence of water on Earth is one great mystery

Evidence at hand indicates that, when it formed about 4.6 billion years ago, Earth was a pretty hot place. Hence, researchers with the European Space Agency claim that it would have been downright impossible for a hypothetic original water content to survive and not simply boil off.

The thing is, in this day and age, nearly two thirds of our planet's surface is covered in water, be it fresh or salty. If young Earth was too hot to hold on to any water reserves, how was it that seas and vast oceans came to form on our planet?

As detailed in the journal Science, scientists suspect that the water now covering most of our planet was delivered to Earth from space. However, they still haven't figured out whether it was comets or asteroids that were kind enough to make this very special delivery.

Whatever celestial bodies brought water to Earth, they probably did so some 800 million years after our planet's formation. Otherwise, the water would have been exposed to some seriously intense temperatures that would have chased it away.

It's doubtful that comets brought water to Earth

In a statement, scientists with the European Space Agency explain that, according to data obtained with the help of the Rosetta spacecraft, the water that is part and parcel of Comet 67P/Churyumov-Gerasimenko is very much different to the one found on Earth.

Thus, it appears that this celestial body packs a whole lot of heavy water molecules, each of which comprises a run-of-the-mill hydrogen atom, a deuterium atom, and an oxygen atom. In case anyone was wondering, deuterium is pretty much like hydrogen, except that its nucleus contains one extra neutron.

By comparison, just 3 out of every 10,000 water molecules on Earth are heavy ones. Scientists say that, if it were true that our planet got a hearty fraction of its water from Kuiper Belt comets like 67P/Churyumov-Gerasimenko, heavy water molecules should be a more common sight on our planet.

Admittedly, it was back in 2011 that the European Space Agency's Herschel Space Observatory found that comet 103P/Hartley 2, which too originates from the Kuiper Belt, had a deuterium-to-hydrogen ratio identical to that documented on Earth. Still, researchers say that this does not mean that water was delivered to our planet by Kuiper Belt objects.

This is because, even supposing that Earth got hit by an army of 103P/Hartley 2-like comets eons ago, it would have taken just one space body similar to 67P/Churyumov-Gerasimenko to seriously mess up the water on our planet and deliver a whole lot of deuterium atoms to it.

As far as comets originating from the Oort Cloud are concerned, scientists point out that it was back in 1986 that the Giotto probe studied Halley's Comet and found it to contain twice as many heavy water molecules than regular water on Earth does. The same is probably true about its siblings.

Asteroids are the most likely benefactors, researchers say

In light of these new findings, researchers point the finger at asteroids as the celestial bodies most likely to have delivered water to our planet billions of years ago. They say that, even if individual asteroids do not have a high water content, an army of such bodies would have surely got the job done.

“Of the 11 comets for which measurements have been made, it is only the Jupiter-family Comet 103P/Hartley 2 that was found to match the composition of Earth’s water, in observations made by ESA’s Herschel mission in 2011,” the scientists behind this investigation say.

“By contrast, meteorites originally hailing from asteroids in the Asteroid Belt also match the composition of Earth’s water. Thus, despite the fact that asteroids have a much lower overall water content, impacts by a large number of them could still have resulted in Earth’s oceans,” they add.

Asteroids said to have brought water to our planet (5 Images)

Scientists claim asteroids brought water to our planet
Infographic details the heavy water thus far documented in spaceRosetta photo of Comet 67P/Churyumov-Gerasimenko
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