Rosetta finds oxygen on comet, upending what we know about planet formation

European Space Agency comet-chaser Rosetta has unexpectedly detected abundant molecular oxygen in the coma of comet 67P/Churyumov–Gerasimenko. The finding will force a re-think of our theories of planet and com et formation.

“We weren’t really expecting to detect O2 at the comet – and in such high abundance – because it is so chemically reactive, so it was quite a surprise,” says Kathrin Altwegg of the University of Bern, and principal investigator of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument, ROSINA.

“It’s also unanticipated because there aren’t very many examples of the detection of interstellar O2. And thus, even though it must have been incorporated into the comet during its formation, this is not so easily explained by current solar system formation models.”

Oxygen is the third most abundant element in the Universe, but the simplest molecular version of the gas, O2, while common on Earth is surprisingly rare elsewhere because it is highly reactive and readily binds with other atoms and molecules.

As a result, any pure oxygen managed to survive from the formation of the solar system from a cloud of dust and gas should, according to the meddling, have been reprocessed by now.

The amount of molecular oxygen detected on the comet showed a strong relationship to the amount of water, suggesting that their origin on the nucleus and release mechanism are linked.

The scientists say that if the oxygen is present throughout the body of the comet and not just at its surface, then it is is probable that molecular oxygen was present at the time the comet formed.

They say that raises two questions. First, how did molecular oxygen become trapped in the icy crystals of the? And second, how has the oxygen remained pure for so long?

The findings have been published in Nature.

Bill Condie

Bill Condie

Bill Condie is a science journalist based in Adelaide, Australia.

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