Rosetta mission provides new intel about origin of water on Earth

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Dec 11, 2014, 10:40 AM EST

The European Space Agency (ESA) made history recently with its Rosetta mission to land a spacecraft on a comet, and now that awesome feat is bringing out some new discoveries.

Though Earth is covered with water, scientists believe all that H2O actually has an extraterrestrial origin. As Popular Science notes, the solar system was an extremely hot place when Earth and the sun were being born, and all that heat would’ve probably boiled any pre-existing water off our planet.

So scientists believed water either came from comets from the Oort Cloud, which encircles the solar system; comets from the Kuiper Belt, which orbit the sun between Neptune and Pluto; and asteroids from the belt between Mars and Jupiter. They essentially ruled out the Oort Cloud 30 years ago, so that leaves just two options.

The magazine further explains that a study of the water found on Rosetta’s Comet 67P/Churyumov-Gerasimenko shows it’s extremely different from the water we have on Earth:

To figure out where our water came from, scientists look at its molecular composition. Water can be composed of regular hydrogen atoms, which have just one electron and one proton. But sometimes a hydrogen atom picks up an extra neutron, and then it’s called deuterium. Deuterium behaves the same as hydrogen, it’s just “heavier”. It’s also extremely rare on Earth. Now, 325 million miles away, the Rosetta mission has measured the ratio of deuterium to hydrogen on Comet 67P/Churyumov-Gerasimenko—and it turns out the comet’s water composition is very different from Earth’s.

Why’s that such a big deal? Because it disproves a previous finding, which led scientists to believe that water on Earth originated from the Kuiper Belt. Measurements from the Hartley 2 comet, which hails from the Kuiper Belt, looked like an excellent match for Earth. So scientists took that to mean our water probably came from there. But Comet 67P also comes from the Kuiper Belt, and its water is nothing like what we have on Earth. So scratch that theory.

So what’s that leave? Asteroids from the belt between Mars and Jupiter. Of course, that’d be one heck of a journey to actually check those comets out and confirm this, so we’ll just put it on the list for a future Mars mission.

(Via Popular Science)