Researchers are looking at the prospect of living other worlds in the universe as resource depletion and overpopulation worries rise, supported by advances in space technology. When assessing if a planet apart from Earth may support life as we know it, scientists frequently look for signs of oxygen. Oxygen accounts for about 20% of Earth’s atmosphere, and it also makes up nearly 50% of the crust and mantle. However, recent studies imply that atmospheric oxygen levels could not be a reliable enough indicator of a planet’s habitability on their own. The method by which oxygen is generated, though, is more telling.
It is estimated that multicellular life on Earth began when the planet produced excess oxygen a couple of billion years ago, and will terminate in another billion years or so when the planet exhausts its supply of this vital gas. As a result, scientists have reason to believe that finding oxygen on an exoplanet is a hallmark of a habitable environment. An article from this year in the journal Science Advances raises concerns that this may be an incorrect strategy.
Most of the oxygen in Earth’s atmosphere is a byproduct of photosynthesis, suggesting that it has a biological origin and serves to sustain various types of life. However, the researchers in this study show that oxygen on a planet might come from non-biological sources as well.
Abiotic oxygen, so called because it is not produced by living organisms, may shed light on why some planets have oxygen molecules in their atmospheres even if they do not host life. Previous work on abiotic oxygen showed that the sun’s UV light could aid in the creation of molecular oxygen from carbon dioxide without the involvement of living organisms. The current research seeks to answer the question of whether or not oxygen could have abiotic sources and paths in space, where life and living activities are absent.
In the course of their investigation, the researchers took into consideration sulfur dioxide, a carcinogenic gas that is found in significant quantities in a number of heavenly bodies and of which significant quantities are released into the atmosphere as a result of volcanic eruptions. More specifically, the researchers investigated how the molecules of sulfur dioxide reacted when exposed to radiation from the sun. The researchers pointed to the findings of an earlier experiment in which molecules of sulfur dioxide were radioactively exposed.
The researchers found that sulfur dioxide molecules changed their forms and underwent double ionization after being subjected to high-energy radiation. During the process of double ionization, the atom of sulfur that was initially located in the middle of the two atoms of oxygen moves to the side, and this leaves the oxygen atoms in close proximity to one another.
Because of the way the molecules are reshaping themselves, the sulfur atom may become detached from the compound and be replaced by a positively charged oxygen molecule. This chain of occurrences is one possible explanation for the presence of oxygen on some locations in the solar system that do not have the conditions necessary for life to exist there. Jupiter’s moons Europa, Ganymede, and Io are all good instances of planets with similar terrains. It is important to note that Io is the most active place in the entire solar system; as a result, it is highly unlikely that it could ever support life systems comparable to those on Earth. Both Europa and Ganymede lack the necessary quantities of oxygen for any kind of life to exist on them.
Oxygen is still an essential ingredient for the maintenance of life systems in the cosmos that are analogous to those on Earth. However, the findings of this recent study demonstrate that the simple existence of oxygen on a surface is not necessarily sufficient justification to consider the surface as a potential new habitat. The route that oxygen takes is also a significant factor in the process. As a result of this, it is still extremely important that, in addition to continuing the search for other habitats, sufficient priority is also given to the preservation of Earth and its resources.