The factor of oxygen in the atmospheres of exoplanets may be more important in the search for alien life than previously thought. It is not about the fact of whether there is oxygen in the atmosphere of a planet, but whether there is enough oxygen to allow technological life to develop there.

This is stated in a study by University of Rome astronomer Amedeo Balbi and University of Rochester astrophysicist Adam Franco. The scientists' study is published on the arXiv preprint portal and has yet to be peer-reviewed by the scientific community.

The search for extraterrestrial intelligence has centered on finding high-tech things on distant planets: radio signals, giant shining cities, interstellar probes or Dyson spheres.

But creating all these things requires two important conditions. The first of these assumes that the aliens are capable of working with iron. The second, and more important, brings scientists back to trivial matters: to work with iron, the aliens must be able to start the fire that will be needed for all the complex manufacturing processes.

And this is where oxygen plays a very important role. If it's less than 16%, or even 18.5%, in the planet's atmosphere, the flame simply won't burn.

Scientists explain that the lack of fire also affects the fact of survival of civilization. After all, if the aliens cannot start a fire, they will not have the ability to cook food, get heat to survive in harsh climates, or travel to colder regions. They will lack the ability to draw in the dark depths of caves. And these are all important evolutionary milestones.

No fire also means no smelting or metalworking, no energy for machines and no industry that could produce radio antennas, solar panels or spaceships.

Such a civilization would never be able to communicate with us or explore space as scientists on Earth do.

In other words, as Balby and Frank emphasized, astronomers looking for signs of high-tech alien civilizations should focus their efforts on planets with oxygen-rich atmospheres.

At the same time, they do not exclude the possibility that there are civilizations built without the use of fire, but they will be invisible to Earth-based researchers and may be detected only by direct contact in the future.

That said, Balbi admitted in an interview with Inverse that figuring out how many planets have enough oxygen in their atmospheres to allow aliens to use fire will not be easy.

"The amount of atmospheric oxygen depends on the interaction of many phenomena, including geology, astrophysics, climate, biology, etc. We are still unable to make reliable predictions for typical planets. We certainly need more data from exoplanets and more theory," he said.

To do that, he said, we need more detailed measurements of exoplanet atmospheres and more computer modeling of how planets form and evolve.

Earlier OBOZREVATEL also told about the fact that the first contact with aliens may end in genocide.

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