Published 15 October 2022 at 14.12
Domestic. Oxygen plays a decisive role for all living things on earth, a large part is formed in biological processes. Now researchers at the University of Gothenburg have found evidence that sulfur dioxide can be broken apart and form oxygen molecules. It may explain the presence of oxygen in the atmospheres of several of Jupiter's moons.
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How was oxygen created? The main explanation is via the biological process photosynthesis that was developed by cyanobacteria, which started the great oxidation event about two billion years ago.
Scientists have long recognized that non-biological processes also contribute – but on Earth dominate photosynthesis. On other celestial bodies where such bacteria are not present, the oxygen can be explained by non-biological processes.
Now researchers at the University of Gothenburg have succeeded in finding a new possible, non-biological way to form oxygen from sulfur dioxide. The molecule is found in the atmosphere of many celestial bodies and large amounts can be ejected during volcanic eruptions.
When the sulfur dioxide molecule is hit by radiation, for example from the sun, of a certain amount of energy, the molecule can be ionized to a twofold plus charge. It can then assume a linear form with the two oxygen atoms in a row and the sulfur atom on one side. Before ionization, sulfur dioxide has a shape reminiscent of the “Mickey Pig” formation of the water molecule.
– During double ionization, two of the electrons that are part of the molecule's bond disappear and this usually means that the angles between the atoms in the molecule change . But in this case so-called roaming occurs, that is, the atoms change places and the molecule takes on a completely new shape, says Måns Wallner, PhD student in physics, in a dispatch.
Once the roaming has taken place is the molecular bond so weak that the sulfur atom can leave and what remains is a single positively charged oxygen molecule O2+, which is then neutralized by receiving an electron from another gas molecule. This process can explain how oxygen has formed in the atmosphere of several of Jupiter's moons such as Io, Europa and Ganymede, despite the lack of biological life.
– We also suggest in our scientific report that this happens naturally on Earth , says Raimund Feifel, professor of atomic and molecular physics and co-author of the report published in the August issue of Science Advances.