The discovery challenges what was previously thought about how our universe was formed.
Scientists have found molecular oxygen - the air that we breathe - in deep space.
The gas was found by the Rosetta Mission, which was launched by the European Space Agency more than 11 years ago.
The mission connected with Comet 67P a year ago.
Astronomer for the Melbourne Planetarium Dr Tanya Hill says the discovery took them by surprise.
"It's amazing to have actually found oxygen, the gas that we breathe, from a comet. Although we have never had a spacecraft orbiting a comet before and so Rosetta has been there orbiting Comet Churyumov-Gerasimenko (67-P) for almost a year now as the comet has approached the sun and then swung around it, and what's exciting about the oxygen discovery is that you don't expect oxygen to be found as a molecule on its own. Normally oxygen likes to bind with other molecules, so you'll get water or carbon monoxide or carbon dioxide, they're all the most abundant gases that you'll find being released from this comet. But to find oxygen on its own, that's pretty amazing."
When scientists first discovered high levels of molecular oxygen on its surface they expected them to change as the comet was buffeted by solar winds.
But the levels stayed the same, suggesting the comet itself was the source of the gas.
Dr Hill says the oxygen was around well before our solar system was formed.
"So it's really got everyone rethinking, where did our solar system come from? And the idea is that perhaps, if the star-forming nebula, the gas that formed our sun and its planets, if that was a little warmer than average, then it's possible that oxygen may well have existed in that nebula and somehow it's become trapped within the comet and it's now being released as the oxygen water is being released."
Dr Hill says the discovery could revolutionise what we thought we knew about our home in the universe.
"It's like a window into the past, it's giving us an idea of what the conditions were like before the sun formed and the planets around it. What's interesting is that it's quite unique. We're used to oxygen being very abundant, we breathe it every day. But the oxygen that is in our atmosphere is only here because of life, because of photosynthesis. So it's quite intriguing to find that there's another place in the solar system where there is oxygen in abundance, but in this case it's not life that's producing it, it may well have been there for billions of years."
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