The Rosetta space probe has been studying the mysterious comet 67P for quite some time, and it continues to send back new information about the strange icy body rocketing through the solar system. According to a report from Nature, scientists with the European Space Agency may have completely changed our understanding of how the solar system was formed by announcing the discovery of gaseous oxygen on 67P.

According to André Bieler, a physicist from the University of Michigan at Ann Arbor and the recent study’s head author, “As soon as we got close enough to the comet, we actually found it right away.” Bieler and his research team were shocked by the presence and just how much O2 was present on the comet, because gaseous oxygen is extremely reactive and would have bonded with other molecules.

67P has been traveling towards the sun since September 2015, and Bieler and his team have used Rosetta’s mass spectrometer to paint a portrait of the molecular makeup on and around the comet. Oxygen makes up about 3.8 percent of the cloud shrouding the comet, which is mostly just water.

Scientists still don’t know exactly where the oxygen came from. Oxygen and water were discovered together, suggesting that a singular process created both as by-products. Researchers believe that the oxygen is left over from the comet’s formation billions of years ago. They think it could have been trapped in small pockets of ice and rock inside the comet’s solid core.

This goes against the historical understanding of the universe, however; oxygen is quick to pair off with hydrogen, and researchers wouldn’t expect to see much gaseous O2 left after the years. Under the right conditions, however, molecular oxygen may have been able to persist on the comet.

A press release outlining the study’s findings can be found here.