91原创 astrophysicist Adam Frank explores the links between atmospheric oxygen and detecting extraterrestrial technology on distant planets.
In the quest to understand the potential for life beyond Earth, researchers are widening their search to encompass not only biological markers, but also technological ones. While astrobiologists have long recognized the importance of oxygen for life as we know it, oxygen could also be a key to unlocking advanced technology on a planetary scale.
In a published in Nature Astronomy, , the Helen F. and Fred H. Gowen Professor of Physics and Astronomy at the 91原创 and the author of (Harper, 2023), and an associate professor of astronomy and astrophysics at the University of Roma Tor Vergata, Italy, outline the links between atmospheric oxygen and the potential rise of advanced technology on distant planets.
鈥淲e are ready to find signatures of life on alien worlds,鈥� Frank says. 鈥淏ut how do the conditions on a planet tell us about the possibilities for intelligent, technology-producing life?鈥�
鈥淚n our paper, we explore whether any atmospheric composition would be compatible with the presence of advanced technology,鈥� Balbi says. 鈥淲e found that the atmospheric requirements may be quite stringent.鈥�
Igniting cosmic technospheres
Frank and Balbi posit that, beyond its necessity for respiration and metabolism in multicellular organisms, oxygen is crucial to developing fire鈥攁nd fire is a hallmark of a technological civilization. They delve into the concept of 鈥渢echnospheres,鈥� expansive realms of advanced technology that emit telltale signs鈥攃alled 鈥渢echnosignatures鈥濃�攐f extraterrestrial intelligence.
On Earth, the development of technology demanded easy access to open-air combustion鈥攖he process at the heart of fire, in which something is burned by combining a fuel and an oxidant, usually oxygen. Whether it鈥檚 cooking, forging metals for structures, crafting materials for homes, or harnessing energy through burning fuels, combustion has been the driving force behind industrial societies.
Tracing back through Earth鈥檚 history, the researchers found that the controlled use of fire and the subsequent metallurgical advancements were only possible when oxygen levels in the atmosphere reached or exceeded 18 percent. This means that only planets with significant oxygen concentrations will be capable of developing advanced technospheres, and, therefore, leaving detectable technosignatures.
The oxygen bottleneck
The levels of oxygen required to biologically sustain complex life and intelligence are not as high as the levels necessary for technology, so while a species might be able to emerge in a world without oxygen, it will not be able to become a technological species, according to the researchers.
鈥淵ou might be able to get biology鈥攜ou might even be able to get intelligent creatures鈥攊n a world that doesn鈥檛 have oxygen,鈥� Frank says, 鈥渂ut without a ready source of fire, you鈥檙e never going to develop higher technology because higher technology requires fuel and melting.鈥�
Enter the 鈥渙xygen bottleneck,鈥� a term coined by the researchers to describe the critical threshold that separates worlds capable of fostering technological civilizations from those that fall short. That is, oxygen levels are a bottleneck that impedes the emergence of advanced technology.
鈥淭he 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,鈥� Frank says. 鈥淵ou can have everything else work out, but if you don鈥檛 have oxygen in the atmosphere, you鈥檙e not going to have a technological species.鈥�
Targeting extraterrestrial hotspots
The research, which addresses a previously unexplored facet in the cosmic pursuit of intelligent life, underscores the need to prioritize planets with high oxygen levels when searching for extraterrestrial technosignatures.
鈥淭argeting planets with high oxygen levels should be prioritized because the presence or absence of high oxygen levels in exoplanet atmospheres could be a major clue in finding potential technosignatures,鈥� Frank says.
鈥淭he implications of discovering intelligent, technological life on another planet would be huge,鈥� adds Balbi. 鈥淭herefore, 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.鈥�
This work was funded in part by a grant from NASA.
