An international team of astronomers is proposing that extraterrestrials would likely be unable to develop advanced technologies unless they are on a planet possessing one key life-supporting component familiar to Earthlings: high levels of atmospheric oxygen.
Astrobiologists hunting for the first definitive signs of life outside of Earth often target planets that likely contain liquid water, a key component for virtually all life on Earth. Now, astrophysicists Adam Frank from the University of Rochester and Amedeo Balbi from the University of Roma Tor Vergata have published research in Nature Astronomy that could help redefine our search for intelligent life in the universe.
Their study focuses on the vital role of atmospheric oxygen in the development of advanced technology on distant planets, introducing the concept of what they call an “oxygen bottleneck.” Mainly, the astrophysicists argue that oxygen is essential not just for life as we know it, but more critically, for the production of fire.
Targeting Planets with High Oxygen Levels May Be Key to Locating Intelligent Extraterrestrials
Fire results from open-air combustion, where a fuel source reacts with an oxidant such as oxygen. While combustion itself is a natural occurrence, the controlled use of fire is recognized as one of the earliest human technological innovations, ultimately forming the backbone of technological advancement on Earth. From cooking to metallurgy, combustion has powered the progress of human civilization.
Frank and Balbi’s research revealed that significant technological developments, like metallurgical advancements, only became possible when Earth’s atmospheric oxygen levels exceeded 18%. This implies that a similar threshold of oxygen concentration might be necessary for advanced technology (and thus intelligent life) to evolve on other planets.
Interestingly, while oxygen is necessary for the complex life and intelligence known to us, its levels need to be higher to support technological advancements. This introduces the “oxygen bottleneck” theory, suggesting that a planet might harbor biology or even intelligent creatures in an oxygen-deficient environment, but it will not progress to a technological civilization without sufficient oxygen to support fire and subsequent technological processes like fuel utilization and metal melting.
“You might be able to get biology—you might even be able to get intelligent creatures—in a world that doesn’t have oxygen,” Frank explained in a statement, “but without a ready source of fire, you’re never going to develop higher technology because higher technology requires fuel and melting.”
Advanced Technologies and the Oxygen Bottleneck
Frank and Balbi’s study suggests prioritizing the search on planets with high oxygen levels, as these are more likely to harbor technologically advanced extraterrestrials capable of producing detectable technosignatures. “The presence of high degrees of oxygen in the atmosphere is like a bottleneck you have to get through in order to have a technological species,” Frank stated. “You can have everything else work out, but if you don’t have oxygen in the atmosphere, you’re not going to have a technological species.”
While the “oxygen bottleneck” theory is compelling, it’s important to consider the possibility of alternative biochemistries that do not rely on oxygen for technological advancement. Life as we know it depends heavily on oxygen, but extraterrestrials in other regions of the cosmos may have evolved under very different conditions, forcing them to utilize elements other than oxygen to survive, and perhaps even produce forms of technology.
The researchers concede that their work is still hypothetical as no life outside of Earth has yet been found. Nonetheless, given the limited budgets and technologies available to search for life outside Earth, they believe their research into an oxygen bottleneck should at least serve as a guide to those searching for extraterrestrials capable of making and using advanced technologies.
“The implications of discovering intelligent, technological life on another planet would be huge,” says Balbi. “Therefore, we need to be extremely cautious in interpreting possible detections.”
“Our study suggests that we should be skeptical of potential technosignatures from a planet with insufficient atmospheric oxygen.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at firstname.lastname@example.org.