In their ongoing mission to explore the possibility of life outside our own pale blue dot, scientists are broadening their scope beyond just biological indicators to include technological signs as well. Astrobiologists have always acknowledged oxygen’s vital role in supporting life as it exists on Earth, yet there’s growing belief that oxygen may also play a crucial part in revealing sophisticated technology at a planetary level.

The multi-university research, published in Nature Astronomy, provides a new angle on the hunt for extraterrestrial life. Their findings imply that oxygen—generally recognized for supporting life—may also be essential to advancing sophisticated technologies on other worlds. They found that controlled fire, which is essential for everything from making metal tools to spaceship, can only work inside atmospheres with at least 16 percent oxygen.

“We are ready to find signatures of life on alien worlds,” said Adam Frank, a University of Rochester professor of physics and astronomy. “But how do the conditions on a planet tell us about the possibilities for intelligent, technology-producing life?”

Oxygen and alien fire

The researchers present the idea of “technospheres,” which they define as highly developed technological domains on far-off planets that may release distinct “technosignatures.” These signals might point to the existence of conscious life outside of Earth. Their argument’s central claim centers on oxygen’s role in facilitating technological advancement, especially through combustion, a fundamental aspect of human progress.

On Earth, technological advancement demanded easy access to open-air combustion, the fundamental process of fire in which something burns by combining a fuel and an oxidant, typically oxygen. Whether it’s cooking, forging metals for structures, crafting materials for homes, or harnessing energy through burning fuels, combustion has been the driving force behind industrial societies.

From a historical perspective, the scientists point out that major technological advances on Earth, like the controlled use of fire and advances in metal production, were only made feasible when atmospheric oxygen levels attained or surpassed 18 percent. Earth’s atmosphere is comprised of 21 percent oxygen. This suggests that the evolution of sophisticated technology on other worlds might require an oxygen content comparable to ours.

The study introduced the phrase “oxygen bottleneck” referring to the atmospheric oxygen threshold at which a planet can sustain life and a highly developed civilization. They contend that even though lower oxygen levels could support simple life forms and even sentient beings, they are insufficient for the emergence of a society with sophisticated technology.

“You might be able to get biology—you might even be able to get intelligent creatures—in a world that doesn’t have oxygen, but without a ready source of fire, you’re never going to develop higher technology because higher technology requires fuel and melting,” Frank said. “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. 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.”

The researchers suggest planets with high oxygen levels should be prioritized when searching for indications of intelligent life. This tactic represents a substantial change in our current methodology.

Frank and the University of Roma Tor Vergata’s Amedeo Balbi advise against hastily interpreting possible technosignatures from planets with low atmospheric oxygen content. Finding intelligent, technological life on another planet would be a huge discovery, and any evidence must be carefully and thoughtfully analyzed.

“The implications of discovering intelligent, technological life on another planet would be huge,” Balbi said. “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.”