First Rosetta findings throw origins of our oceans into question

11 Dec 2014

Image of Comet 67P via ESA

Some of the first findings from the Rosetta mission have raised questions about the origins of our oceans, after water vapour on comet 67P has been found to be radically different than water in Earth’s oceans.

While the very origin of life on Earth is constantly under debate, one theory surrounding the potential origins of our oceans came from the idea that comets that collided with Earth may have at some point provided the catalyst that created the oceans.

Current scientific understanding suggests that when the Earth was formed about 4.6bn years ago, the planet would have been too hot for any water to form. This leaves the comet theory, which has been considered to be quite credible.

However, samples taken from comet 67P on 6 August following the Rosetta spacecraft’s ROSINA instrument’s first rendezvous with the enormous chunk of space debris found it contained more than three times the amount of deuterium – a form of hydrogen with an additional neutron – to normal hydrogen than would be found in Earth’s water.

This recent discovery could suggest that much of the comets we have been able to analyse so far can differ in deuterium quantities, depending on where they originated from.

Click the graphic for a larger infographic. Image via ESA

Still hope for ocean asteroid theory

According to the European Space Agency (ESA) which undertook the mission, of the 11 comets for which measurements have been made, only the Jupiter-family comet 103P/Hartley 2 was found to match the composition of Earth’s water, in observations made by the ESA’s Herschel mission in 2011.

Meanwhile, asteroids from the asteroid belt that exists between Mars and Jupiter have been shown to harbour water that equates with that found on Earth, which keeps the theory of our oceans being supplied by asteroids as a possibility.

Kathrin Altwegg, principal investigator for the investigation, said, “This surprising finding could indicate a diverse origin for the Jupiter-family comets – perhaps they formed over a wider range of distances in the young solar system than we previously thought.”

Matt Taylor, ESA’s Rosetta project scientist, added, “We knew that Rosetta’s in-situ analysis of this comet was always going to throw up surprises for the bigger picture of solar system science, and this outstanding observation certainly adds fuel to the debate about the origin of Earth’s water.”

Colm Gorey was a senior journalist with Silicon Republic