Are Earth's Oceans Made Of Extraterrestrial Material?

**Liffrea** · 11-12-2009, 03:37 PM

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.

http://www.sciencedaily.com/releases...1111110045.htm

**Svipdag** · 11-13-2009, 11:16 PM

This is an interesting hypothesis. However, we lack sufficient information to exclude a terrestrial origin for the oceans. We do not, probably cannot know how much water was present in the planetesimal material from which the Earth was accreted. Most of the water which had not been adsorbed onto or trapped between the planetesimal particles during accretion would have been driven out of the interior of the developing solar system by the increased radiation flux from the sun during the T-Tauri phase of its evolution, if, indeed it passed through such a phase.

The presence of far more gases in the outer portions of the solar nebula than in the inner part, leading to the formation of rocky planets near to the Sun and gas giants further out does suggest some process which expelled gases from the interior of the solar nebula to the exterior after the terrestrial planets and, possibly, the rocky cores of some of the gas giants, had accreted.

It has not been established that ice was not a major constituent of the planetesimal material which had already been accreted and which would have been outgassed during the gravitational contraction of the intitially low- density accumulations of planetesimal material which formed the terrestrial planets, forming their primordial atmospheres and hydrospheres.

**Octothorpe** · 11-14-2009, 01:17 AM

I seem to remember a paper from the '90s that stated that micro-comets were still impacting the upper atmosphere and adding (infinitesimal, now) amounts of water to the hydrosphere. Have I remembered it wrong, or did the evidence turn out to be 'all wet'?

**Svipdag** · 11-14-2009, 02:05 AM

As far as I know, this is still considered to be true. What we don't know is whether the contribution of water from this source was ever much greater than it is today.

**Svipdag** · 11-14-2009, 02:09 AM

Of course, the original question has to be answered "Yes". The Earth itself was accreted from "extraterrestrial" material. The question is what happened to the cosmic water before it became part of Earth's hydrosphere.