Rosetta results: Comets 'did not bring water to Earth'

Results from Rosetta's mission show the water on the icy mass is unlike the water on our planet. The results were published in the journal science. The authors conclude it is more likely that the water came from asteroids, but other scientists say more data is needed before comets can be ruled out. Although Philae's batteries ran out, Rosetta keeps on analysing the "ice mountain".

This unprecedented, close-up look at a comet is helping scientist to answer the fundamental question of whether a bombardment of these primitive bodies brought water to earth billions of years ago. And the latest findings, gathered by Rosetta's instruments, which consists of two mass spectrometers that "sniff" the gas that streams out off the surface of comet 67P, suggests this may not be the case.

Water on Earth has a distinctive signature. While the vast majority of liquid on our planet is made up of hydrogen and oxygen atoms, very occasionally a hydrogen atom will be replaced with a deuterium atom. On Earth for every 10000 water molecules, three deuterium atoms can be found. This water has the same chemical properties as H2O, but is heavier on mass. Professor Altwegg, from the university of Bern in Switzerland, who is Rosetta's principal investigator said: "This ratio between heavy and light water is very characteristic. You cannot easily change it and it stays for a long time. If we compare the water in comets with the water we have on Earth, we can definitely say if the water on Earth is compatible with the water on comets".