(ORDO NEWS) — Scientists have proven that oxygen can be produced in large quantities not only as a result of the activity of microorganisms, but also due to powerful volcanic activity on “dead” worlds.
Detecting oxygen in an exoplanet’s atmosphere is key to whether it could harbor life. On Earth, photosynthetic organisms take in carbon dioxide, sunlight, and water and produce sugars and starches for energy.
Oxygen is a by-product of this process, so if we can find oxygen elsewhere, it could be a beacon of sorts.
But the researchers also insist that oxygen in an exoplanet’s atmosphere doesn’t always indicate the presence of life. It becomes a biomarker only if we exclude all other ways of producing oxygen.
The problem is that scientists can’t rule them out.
The earth is saturated with oxygen. It makes up 46% of the earth’s crust and about the same percentage of the mantle, and the atmosphere is about 20% oxygen.
The presence of oxygen is associated with the Great Oxidation Event, which occurred about two billion years ago. Ancient cyanobacteria developed pigments that absorb sunlight and use it for photosynthesis.
Oxygen is a by-product of photosynthesis, and life has had several billion years to store oxygen in the atmosphere, mantle, and crust.
So if scientists find oxygen in an exoplanet’s atmosphere, it’s a strong indication that life might be at work. Simple life can boil in the planet’s oceans, absorbing sunlight and releasing oxygen.
However, a new study has identified a source of oxygen that is independent of life.
Sulfur is not uncommon in celestial bodies, and since volcanoes produce sulfur and pump it into the atmosphere, terrestrial volcanic exoplanets can also contain oxygen in their atmospheres. And the vital activity of bacteria has nothing to do with it.
Instead, the star’s high-energy radiation can ionize the sulfur dioxide molecule. The formula for sulfur dioxide is SO2, and when it ionizes, the molecule rearranges itself and becomes a “double positively charged system.”
It then has a linear shape with both oxygen atoms adjacent to each other and sulfur atoms at the other end. The oxygen atoms are free to drift in random orbits until they form new compounds.
But the constituent molecules may not be converted back to SO2. Instead, the sulfur can decay, leaving a simple positively charged oxygen molecule.
Then the positive charge can be neutralized by attracting an electron from another molecule. The result is just molecular oxygen (O2).
This may explain why astronomers find traces of oxygen on Io, Ganymede, Europa and other celestial bodies that are completely unsuitable for the existence of organic life due to extreme conditions.
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