by Alien hunters should look for technological life on planets with high abundances of oxygen in their atmospheres, according to new research that aims to improve the search for handouts from extraterrestrial civilizations.
Amedeo Balbi, who is an associate professor of astronomy and astrophysics at the University of Roma Tor Vergata in Italy, and Adam Frank, who is a professor of physics and astronomy at the University of Rochester in the US, argue that a planet’s atmosphere must be contained. at least 18% oxygen to facilitate technological civilization. The reason for this, they say, is simple: fire needs oxygen.
“You might be able to find biology – you might even be able to find intelligent creatures – in a world where there is no oxygen,” Frank said 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.”
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Balbi and Frank describe the 18% level as an “oxygen bottleneck” that could prevent intelligent life from developing sophisticated technology that we could detect through radio signals. This includes any foreigner city lights, Dyson swarms infrared emissions or perhaps megastructures transiting alien stars. This concept joins other such bottlenecks that scientists face in the search for extraterrestrial life, including one that dictates the evolution of multicellular life, one that deals with the development of tool-using intelligence, and even one that controls whether an alien society can avoid being blown up. own up. Together, they form the “Great Filter”, a concept introduced by economist and futurist Robin Hanson when he described a series of barriers to the development of technological life in an attempt to explain why it is scarce in our galaxy.
An exoplanet with an oxygen abundance below 18% would not be sufficient for long open air combustion, the team says. This would limit metallurgy, for example, and restrict the burning fossil fuels. Although the absence of the environment could lead to a cleaner environment, without the former it would be difficult to sustain any kind of widespread industry or create the materials necessary to build radio transmitters that can transmit signals. detectable by our sending devices.
Ar Worldthe abundance of oxygen in our atmosphere 21%, but this was not always the case. For the first half of its life, the Earth’s atmosphere was dominated by nitrogen and carbon dioxide, with perhaps only 0.001% oxygen. Then, about 2.4 billion years ago, the abundance of molecular oxygen in our planet’s atmosphere began to increase dramatically. This increase is attributed to the evolution of cyanobacteria that produce oxygen as a waste product, but it is also known that the increased oxygen levels harmed the anaerobic life forms of the time, reducing the abundance of hydrogen sulfide and methane necessary for their life. .
Therefore, the arrival of extra oxygen in the Earth’s atmosphere is sometimes called an “oxygen disaster” because many microbial species were wiped out.
Within 400 million years of this event — two billion years ago — atmospheric oxygen levels were at 10%, meaning they would still be too low for Balbi and Frank’s barrier.
Therefore, the duo’s research focuses on the types of planetary systems that make the search for extraterrestrial information (SETI) should be focused on during the hunt for technosignatures.
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“Targeting planets with high oxygen levels should be prioritized because the presence of high oxygen levels in exoplanet atmospheres could be a big clue in finding potential technosignatures,” Frank said.
Furthermore, given how long it took for Earth’s oxygen levels to rise above 18%, it might be wise to target older planets that would have had enough time to develop their own oxygen stores.
The research can even be used to rule out false alarms, Balbi says, suggesting that “we should be suspicious of potential technologies from planets with insufficient oxygen in the atmosphere.”
The results also suggest that if technological life on Earth can continue to flourish for the next few billion years, an additional challenge may lie ahead. I 2021 studies by Kazumi Ozaki of Toho University in Japan and Christopher Reinhard of NASA and the Georgia Institute of Technology in Atlanta, it was shown that as the sun gets older and brighter to produce more heat our planet in turn, Earth’s atmosphere will become deoxygenated, with oxygen levels falling below 10%. Of course, a billion years is a long time to be able to prepare; by then, our descendants might have the technology to mitigate this, or Earth might be left entirely.
The research was published on December 28, 2023 in the journal Natural Astronomy.
