Oxygen levels on exoplanets reveal presence of alien technology

Scientists have long looked to oxygen when searching for signs of life beyond Earth. This gas sustains breathing and enables animals and plants to flourish. Now, researchers suggest that oxygen might also point to advanced technology.

If an exoplanet’s atmosphere holds enough oxygen, it may not only support organisms but also help them spark fire, build structures, and craft machinery.

A study in Nature Astronomy presents this view, highlighting oxygen’s value as more than just a sign of biology.

Oxygen, civilization, and technology

Leading this research are Adam Frank, the Helen F. and Fred H. Gowen Professor of Physics and Astronomy at the University of Rochester, and Amedeo Balbi, an associate professor of astronomy and astrophysics at the University of Roma Tor Vergata, Italy.

Together with their team, they set out to explore whether oxygen is a key factor in allowing extraterrestrial civilizations to emerge and thrive through the development of technology.

“We are ready to find signatures of life on alien worlds,” Frank says. “But how do the [oxygen] conditions on a planet tell us about the possibilities for intelligent, technology-producing life?”

This question drives efforts to examine oxygen’s role beyond respiration and metabolism, especially in relation to large-scale industrial activities.

Why oxygen matters for civilizations

Photosynthesis on Earth accounts for the bulk of our oxygen on our planet, thanks to countless organisms that use sunlight to make food.

Because this process produces so much oxygen, it has been considered a biosignature. A planet with significant oxygen levels hints that life may be present, but Frank and Balbi argue that oxygen also has a second function.

“In our paper, we explore whether any atmospheric composition would be compatible with the presence of advanced technology,” Balbi says. “We found that the atmospheric requirements may be quite stringent.”

The link to technology comes from open-air combustion. Smelting metals, cooking food, and powering engines all rely on oxygen.

Any alien civilization that forges metals would need a certain percentage of oxygen in its air to keep fires burning reliably. That percentage, according to Earth’s history, appears to be around 18 percent.

Fire and the 18% threshold

“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 says, “but without a ready source of fire, you’re never going to develop higher technology because higher technology requires fuel and melting.”

He calls attention to fire’s role in shaping tools, infrastructure, and energy production. Metalworking, for instance, depends on sustaining flames hot enough to melt ore and craft refined structures.

Frank and Balbi refer to this requirement as an “oxygen bottleneck.” A planet might host life forms of various kinds, yet remain stuck without the combustion needed to fuel industrial breakthroughs.

“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 says.

“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.”

Oxygen + technology create “technosignatures”

Frank thinks that exoplanets with oxygen levels at or above 18 percent should be at the top of our search list.

“Targeting 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,” Frank says.

Planets that exceed this level may have the capacity for factories, infrastructure, or communication networks.

Balbi notes that interpreting any possible signal of intelligent life will be challenging.

“The implications of discovering intelligent, technological life on another planet would be huge,” adds Balbi. “Therefore, we need to be extremely cautious in interpreting possible detections.

Their study suggests that astronomers should be skeptical of potential technosignatures from a planet with insufficient atmospheric oxygen.

Technosphere vs. biotechnosphere

Frank and Balbi’s perspective also covers the idea of a technosphere, which is the collective output of an advanced civilization.

Factories, vehicles, and power grids all fit under this label. They rely on resources provided by the planet’s biosphere but stretch beyond purely natural processes.

Burning fuels in open air has been central to every major industrial leap, from forging steel to generating electricity.

When these technologies reach a global scale, they form a biotechnosphere. This term applies to the interplay of living systems and technology — essentially, how organisms and machines coexist.

On Earth, that includes everything from smartphones to farms, all running side by side. A well-established biotechnosphere might produce clear signals in the atmosphere: waste gases, unusual heat patterns, or chemicals not normally found in nature.

Balancing machines and ecosystems

History shows that as technology expands, it can sometimes damage or alter environments. Factories might pump pollutants into the air, while deforestation removes habitats that produce oxygen.

Yet there is an ongoing move toward cleaner energy and more efficient resource use. If any alien civilization follows a similar path, we might detect certain byproducts in the form of greenhouse gases or engineered molecules.

Though the focus is on oxygen, other factors matter too, such as temperature and access to metals or fuels. A planet may need stable conditions for life to progress to a point where industry becomes possible.

That said, Frank and Balbi’s findings highlight how oxygen stands out among these factors, because it directly enables combustion processes.

Fire and progress in Earth’s past

Earth’s own development through advances in technology offers insight into how vital oxygen has been for technical achievements.

Once our atmosphere had enough of it, humans learned to manipulate fire for cooking and for making stronger materials.

From simple smithing to modern manufacturing, every stage of growth involved open-air combustion.

“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,” Frank says.

This idea underlines how a single factor — oxygen — can open or close the door to industrial progress, altering a planet’s entire future path.

Oxygen, technology, and next steps

Observatories now in the works may soon gather data about exoplanet atmospheres in detail. Detecting a high oxygen content could mark a world that supports advanced living organisms.

The next task is to look for proof of industry or technology, sometimes called technosignatures. These might appear as chemical emissions, radio signals, or specific spectral lines.

If these two checks– oxygen above 18 percent and evidence of artificial activity — both yield results, we will have a strong indication that we share the universe with another technological civilization.

That reality could reshape how we see ourselves and our place among the stars.

Why does any of this matter?

Understanding the significance of atmospheric oxygen can also inspire reflection on our home planet. Human industries rely heavily on combustion, from running cars to powering factories. This has changed Earth’s ecosystems.

As we learn more about how oxygen in an atmosphere enables or limits technology, we might gain new ideas on how to manage our own balance between growth and environmental health.

Ultimately, Frank and Balbi’s argument shows that oxygen may do far more than keep living cells alive. It might be the clearest signal of whether a planet can support the technologies that shape modern societies.

By recognizing the 18 percent threshold, scientists can refine their search for advanced life and possibly move closer to answering the age-old question: Are we alone, or is someone else using fire to reshape their world?

The full study was published in the journal Nature Astronomy.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–