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.