Historic Discovery: Molecular Oxygen Found On Comet 67P

In a historic discovery, molecular oxygen has been found on Comet 67P/Churyumov-Gerasimenko, by the Rosetta spacecraft.

The European Space Agency’s probe detected the presence of dioxygen in a gas being expelled by the comet, and this might challenge our long-held beliefs regarding the beginnings of our solar system.

It is highly surprising that molecular oxygen managed to survive for so long, given that it’s highly reactive with hydrogen.

Theoretically, it should’ve disappeared back when the solar system was formed, approximately 4.6 billion years ago, because at the time, when the planets and the sun were formed, there were huge amounts of hydrogen.

However, it appears dioxygen has endured, and is even present nowadays on the comet, which leaves experts perplexed as to the actual composition of the our early solar system.

The findings have been detailed in a study published on October 28 in the journal Nature, by Andre Bieler, research fellow at the University of Michigan, and Kathrin Altwegg, space scientist at the University of Bern.

The cometary scientists suggest that it’s time to revise the current solar system model, but since their expertise doesn’t extend to that field as well they prefer not to hypothesize regarding what should exactly should be altered.

Currently, their purpose is to conduct further analysis to determine if there might be molecular oxygen on Halley’s Comet as well.

They will be reviewing the observations made by the Giotto probe, an European Space Agency robotic spacecraft which flew by the space object and studied it on March, 12, 1986.

It was actually the first time in history that a probe conducted close-up analysis of a comet, and the mission managed to approach Halley’s nucleus at a distance of 596 kilometers.

Normally, spectral lines of oxygen are too indiscernible to be observed from Earth’s telescopes. Therefore, reviewing information collected by the Giotto spacecraft seems like the best alternative to discover if molecular oxygen might in fact be present on other comets as well.

The Rosetta probe has detected important elements before on Comet 67P/Churyumov-Gerasimenko, after orbiting it for more than a year, starting from August 6, 2014.

In November 12, 2014, the Philae lander detached from the mother ship, and landed on the icy object. This allowed scientists to study emissions of gas and dust, as well as the composition and structure of a comet with unprecedented precision and clarity.

Philae identified water on the surface, but its deuterium-to-hydrogen ratio is extremely dissimilar to that encountered on Earth. This counters the theory that comets from that area of the solar system brought water to our planet, and makes it more likely for asteroids to have been the actual source.

Two instruments known as COSAC (Cometary Sampling and Composition) and Ptomely also detected carbon dioxide and around 16 organic compounds on Comet 67P, and four of them had never been encountered on a comet before: acetamide, propionaldehyde, acetone and methyl isocyanate.

It may be that such elements were actually the building blocks of life on Earth, and even in other parts of the universe.

However, molecular oxygen, found on moons of Saturn and Jupiter, had never been identified before in a cometary coma, which usually has just water, carbon monoxide and carbon dioxide. And yet, it was now revealed thanks to the ROSINA-DFMS (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis).

It seems dioxygen quantities remain constant around the comet, and its presence was noticeable between September 2013 and March 2015, as oxygen appeared less dense when the probe drew farther, and denser as it neared.

One suggestion is that gaseous molecular oxygen dissolved into icy granules which became part of the comet, but that hypothesis seems unlikely, since such gas is rare in our solar system, and would’ve been converted into water.

A more likely theory is that high-energy, radioactive particles collided with the dark nebulae from which the sun emerged, and water broke up into molecular oxygen and hydrogen.

This seems like the most reasonable explanation, given that elements identified in the comet closely resemble those from an interstellar cloud.

Image Source: ESA