For the first time ever, scientists found molecular oxygen on a comet

Washington Post, By Rachel Feltman, October 28

For the first time ever, molecular oxygen has been found on a comet. Comet 67P/Churyumov–Gerasimenko, currently being orbited by the European Space Agency’s Rosetta spacecraft, is the subject of a study published Wednesday in Nature. According to ESA researchers, the oxygen present in the comet’s surrounding gasses has likely been there since the formation of the comet.

“It is the most surprising discovery we have made so far, because oxygen was not among the molecules expected in a cometary coma,” the University of Bern’s Kathrin Altwegg said at a news conference Tuesday held by Nature. Altwegg, one of the new study’s authors, is in charge of Rosetta’s ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis). This instrument is used to “sniff” out the atmospheric composition of the comet.


“We all went a little bit into denial,” she said. The result was so unexpected that the team wanted to be absolutely certain that the oxygen wasn’t the result of some kind of instrumentation failure or contamination. But the oxygen, Altwegg explained, “follows the comet very well.” The team has observed that oxygen levels are higher close to the comet, and disappear as the instrument pulls away.


But no current models of the solar system’s formation would allow for molecular oxygen to get locked away inside a comet. Oxygen is highly reactive, so it’s always been assumed that any molecular oxygen present would bond with the abundantly available hydrogen. The researchers were shocked to see that oxygen could “survive” in its molecular form for billions of years.

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