Water in Distant Comet Similar to That in Earth's Oceans

The Herschel Space Observatory – the largest and most complex telescope ever deployed to space – has recently detected water very similar to that in Earth's oceans in a distant comet. Both types of water exhibited nearly identical compositions, indicating that impactors may have brought water here.

These observations have tremendous implications when it comes to analyzing our planet's deep history. It could be that, at one time, all the water that currently flows on Earth's surface was nothing more than countless balls of frozen ice and dust roaming through the solar system – a group of comets.

That may very well be the case, according to the new investigation. Some scientists have been arguing that the oceans could have not appeared naturally on our planet for many years, but thus far clear evidence to support this point of view has been lacking.

When the planet first formed out of a ball of molten lava – about 4.5 billion years ago – the tremendous temperatures would have ensured that all water potentially trapped within the solidifying globe would have evaporated into space.

Obviously, this didn't stop about 75 percent of the planet's surface from becoming covered in the chemical at this point. What the Herschel data are suggesting is that comets carrying frozen water may have been responsible for depositing huge amounts of the stuff on the planet.

In order to arrive at these conclusions, experts trained the Herschel telescope on comet Hartley 2. The observatory used its Heterodyne Instrument for the Far Infrared (HIFI) to conduct the investigations.

“Comet Hartley's deuterium-to-hydrogen ratio is almost exactly the same as the water in Earth's oceans,” explains the leader of the international team of experts that led the study, Paul Hartogh. He is based at the Max Planck Institute for Solar System Research, in Katlenburg-Lindau, Germany.

“Thanks to this detection made possible by Herschel, an old, very interesting discussion will be revived and invigorated. It will be exciting to see where this discovery will take us,” adds ESA Herschel project scientist Göran Pilbratt.

At this point, the telescope is being aimed at other comets roaming the solar system. Experts hope to be able to conduct similar measurements using HIFI, and thus check to see whether the same isotopic signatures are also found on other space bodies as well.

If that indeed turns out to be the case, then it would be safe to assume that the vast majority of water on our planet is extraterrestrial in origin, an European Space Agency press release suggests.