quarta-feira, 10 de novembro de 2010

Earth May Have Had Water From Day One

November 2010
By David Shiga
Magazine issue 2785

In the beginning, there was water. Earth's life-sustaining liquid came from the dust from which the planet was born, a new look at these particles suggests, and not simply from collisions with objects that later crashed into the planet from space.

The origin of the oceans has long been a mystery. Earth's birthplace in the dusty nebula around the young sun should have been hot enough to keep any water vaporised. So it seemed clear that the dust that coalesced to create Earth was bone dry, and that water somehow arrived later.

Ice-rich comets or asteroids from farther out in the solar system could have supplied it, but that raises a further problem. Comets are richer in deuterium, a stable heavy isotope of hydrogen, than Earth's oceans. And asteroids should have brought more platinum and other rare elements than have been found. These mismatches are difficult to explain if most of Earth's water came from impacts.

Read the full story at newscientist.com

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