'Sniff' of oxygen around comet reveals Solar System's 'gentle' birth

The discovery is challenging the long established belief that oxygen existed in abundance when sun and planets were created but should have gone by the time when the comet was formed, soon after the birth of solar system about 4.6 billion years ago.

This detection "suggests they (oxygen molecules) were incorporated into the comet during its formation", explained ESA, given that the simplest molecular version of the oxygen, O2, is "highly reactive and readily breaks apart to bind with other atoms and molecules".

The European Space Agency's Rosetta probe has detected molecular oxygen on Comet 67P, raising new questions about the origins of the solar system.

"No current models of the Solar System's formation would allow for molecular oxygen to get locked away inside a comet".

Despite the fact that Rosetta has detected elements such as water, carbon monoxide and carbon dioxide, molecular oxygen wasn't expected at all.

Flickr German Aerospace Center DLRSummertime for Philae Comet 67P Reaches Closest Point to the Sun

The results were published today (October 29) in the journal Nature. "It was the most surprising discovery we have made so far (about the comet)".

Kathrin Altwegg, project leader of the ROSINA mass spectrometer from the University of Bern, Switzerland and a co-author of the study said during a press briefing. Scientists have no answer how the oxygen maintained its pristine state over billions of years.

Nevertheless, scientists are not able to figure out how did oxygen survived in the comet for such a long time.

The only other possibility is that the O2 had been trapped inside the comet and was being released as its host shed its surface material during its close solar encounter. Since the ratio of water to oxygen is remaining constant [in different locations on the comet], it means that molecular oxygen must be present in the whole body [of the comet]. "If it were only on the top surface, we would see a decrease over time of the oxygen to H20 ratio".

With over 3,000 samples - collected from September 2014 to March 2015 as the comet headed toward the sun - the Rosetta team discovered a link to the amount of water (H20) present at the comet.

"Specifically, high-energy particles struck grains of ice in the cold and dense birthplaces of stars, the so-called dark nebulae, and split water into oxygen and hydrogen".

The most likely explanation, according to the researchers, is that the oxygen originated early, before the formation of the solar system.