Why there is so little oxygen in space

Chuck Bednar for redOrbit.com – @BednarChuck

Oxygen is one of the most common elements, with only hydrogen and helium topping it in terms of abundance, so why is there so little breathable oxygen in space?

During the 1970s, astronomers predicted that molecular oxygen (also known as O2) would be one of the three most common interstellar molecule, behind only molecular hydrogen (H2) and carbon monoxide (CO), according to Science. As we now know, that isn’t the case, and O2 has actually only been found in two locations: The Orion Nebula and the Rho Ophiuchi cloud.

In 1998, NASA launched a satellite that they believed would uncover a wealth of undiscovered molecular oxygen in the cosmos, but it only returned positive signals when it was aimed at Earth. In a new ground-based experiment, researchers set out to discover why O2 is so rare.

What they found, according to the publication, is that oxygen atoms fix themselves to stardust, which keeps them from joining together to become molecules. This discovery, reported recently in the The Astrophysical Journal, provides new insight into the unusual chemical conditions that are prevalent when stars and planets form out there in the universe.

Binding energy of oxygen twice previous estimates

As part of their research, astronomers and physicists from Syracuse University, San Jose State University, and the University of Hawaii at Manoa heated water ice and silicate, a pair of solids that make up interstellar dust grains, to find how easy it was for oxygen atoms to escape. They found that the binding energy of oxygen was more than twice previous estimates.

According to Science, the binding energy of water ice was 0.14 electron volts and the binding energy of silicate was 0.16 electron volts – a voltage the authors said is high enough to keep oxygen atoms attached to stardust without being dislodged by the low heat of interstellar clouds.

While oxygen atoms that float away from interstellar dust grains can form molecules, those that are stuck to those particles combine with hydrogen atoms to form water ice (H2O) instead. That water, in turn, can become part of asteroids, comets, or planets, potentially creating the conditions necessary for formation of biological life, the study authors explained.

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