Are Earth's Oceans Made Of Extraterrestrial Material?

Contrary to preconceived notions, the atmosphere and the oceans were perhaps not formed from vapors emitted during intense volcanism at the dawning of our planet.

Francis Albarède of the Laboratoire des Sciences de la Terre (CNRS / ENS Lyon / Université Claude Bernard) suggests that water was not part of the Earth's initial inventory but stems from the turbulence caused in the outer Solar System by giant planets.

Ice-covered asteroids thus reached the Earth around one hundred million years after the birth of the planets.
The Earth's water could therefore be extraterrestrial, have arrived late in its accretion history, and its presence could have facilitated plate tectonics even before life appeared.

The conclusions of the study carried out by Albarède feature in an article published on the 29 October 2009 in the journal Nature.
Space agencies have got the message: wherever there is life there has to be water. Around 4.5 billion years ago, the Earth was bequeathed with sufficient water for oceans to form and for life to find favorable niches in the seas and on the continents resulting from plate tectonics. In comparison, the Moon and Mercury are dry, mortally cold deserts, Mars dried up very quickly and the surface of Venus is a burning inferno.


According to books, the ocean and the atmosphere were formed from volcanic gases and the Earth's interior is the source of volatile elements. However, the rocks of the Earth's mantle are deficient in water (geochemists estimate its concentration at two hundredth percent). The same is true on Earth's sister planets, Venus and Mars.

The main reason proposed by Albarède is that, during the formation of the Solar System, the temperature never dropped sufficiently between the Sun and the orbit of Jupiter for volatile elements to be able to condense with planetary material. The arrival of water on Earth therefore corresponds to a late episode of planetary accretion.
 
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