Scientists participating in the European Space Agency's Rosetta mission were surprised to find molecular oxygen around the comet 67P/Churyumov-Gerasimenko in October, making the first time the essential molecule was seen around a comet. The researchers believe that the O2 (oxygen) was probably trapped in water ice when the comet formed approximately 4.6 billion years ago. Their findings raised their curiosity to whether other comets could also potentially contain the molecule.

Now the findings of a team of researchers that has been looking for oxygen on 1P/Halley, known more commonly has Halley's Comet, suggest that O2 could be common on other comets in the solar system.

Led by Martin Rubin from the University of Bern in Switzerland, the team of researchers were able to find traces of O2 on Halley's Comet.

Publishing their findings on Dec. 4 in the Astrophysical Journal Letters, the researchers found that not only is 02 present on the comet, but also it is the third most abundant species on the celestial icy body.

The researchers used data from the Neutral Mass Spectrometer (NMS) instrument that was on the ESA's Giotto probe that passed Halley's Comet back in 1986. The mission allowed researchers at the time to gather data during their flyby of the comet as they approached the center of Halley at a distance of 596 kilometers. At such a close range, the scientists were able to gather data that includes chemicals of the materials being ejected from the comet.

The data revealed that chemicals ejected were mainly water and monoxide, as well as traces of methane, ammonia, iron and sodium. Looking back on the data, the team also was able to report Halley has significant amounts of molecular oxygen.

"Our investigation indicates that a production rate of O2 with respect to water is, indeed, compatible with the obtained Halley data, and therefore that O2 might be a rather common and abundant parent species," the scientists write in the paper.

Since O2 was found on both 67P/Churyumov-Gerasimenko (which is part of the Jupiter family of comets) and 1P/Halley (part of the Oort cloud family of comets), this may prove their theory that it is possible that oxygen was formed through irradiation of ices during the molecular cloud phase and was trapped before the comet formed.

If this hypothesis is true, this means other comets could also contain molecular O2. This knowledge can help scientists better understand the origins of life and give clues to how the solar system was created.


Photo: NASA | W. Liller

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