Comet’s water ‘like that of Earth’s oceans’

Jason Palmer – 

Comet Hartley 2 contains water more like that found on Earth than prior comets seem to have, researchers say.

A study using the Herschel space telescope aimed to measure the quantity of deuterium, a rare type of hydrogen, present in the comet’s water.

The comet had just half the amount of deuterium seen in comets.

The result, published in Nature, hints at the idea that much of the Earth’s water could have initially came from cometary impacts.

Just a few million years after its formation, the early Earth was rocky and dry; something must have brought the water that covers most of the planet today.

Water has something of a molecular fingerprint in the amount of deuterium it contains, and only about a half-dozen comets have been measured in this way.

All of them have exhibited a deuterium fraction twice as high as the oceans, so the current theory holds that asteroids were likely to be the carriers for water; meteorites that they give rise to have roughly the same proportion of deuterium that the Earth’s oceans contain.

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