A team of scientists has detected tiny quantities of the unreactive volcanic trace gases Krypton and Xenon in Earth's mantle, which reveal an isotopic 'fingerprint' matching that of

The researchers say this means the gases that formed the Earth's atmosphere - and probably its oceans - did not come from inside the Earth but from outer space.

The report published this week in the journal Science demonstrates that the age-old view that volcanoes were the source of the Earth's earliest atmosphere must be put to rest, the researchers suggest.

"Until now, no one has had instruments capable of looking for these subtle signatures in samples from inside the Earth - but now we can do exactly that. From that we now know that the volcanic gases could not have contributed in any significant way to the Earth's atmosphere.

"Therefore the atmosphere and oceans must have come from somewhere else, possibly from a late bombardment of gas and water rich materials similar to comets."

The study is also the first to establish the precise composition of the Krypton present in the Earth's mantle.

Project director Prof Chris Ballentine of The University of Manchester, said: "Many people have seen artist's impressions of the primordial Earth with huge volcanoes in the background spewing gas to form the atmosphere. "We will now have to redraw this picture."

Citation: Greg Holland, Martin Cassidy, Chris J. Ballentine, 'Meteorite Kr in Earth’s Mantle Suggests a Late Accretionary Source for the Atmosphere', Science 2009, Vol. 326(5959), 1522 - 1525; doi: 10.1126/science.1179518