The findings, which baffled the Rosetta team, were published in the journal Nature.
Oxygen is common on Earth, but not elsewhere in the universe. Scientists had certainly never found it on a comet before. What also surprised them was how much there was.
A decade ago, Rosetta the spacecraft and Philae the robot set out to catch comet 67P. Last year, Rosetta dropped Philae onto its surface to study it more closely. The tools on Rosetta already found earlier this year that the comet had its own kind of water.
Comets are of huge interest to scientists because, to human knowledge, they are the most ancient bodies of the solar system – the building blocks from which our sun and planets were formed some 5 billion years ago.
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