What geophysical criteria must exist on exoplanets teach scientists about whether technological civilizations exist throughout the galaxy? This is what a recent study presented at the Europlanet Science Congress and the American Astronomical Society’s Division for Planetary Science (EPSC-DPS2025) hopes to address as a team of researchers investigated the likelihood of extraterrestrial intelligences (ETIs) existing throughout the galaxy based on specific criteria. This study has the potential to help scientists narrow down the criteria for finding ETIs throughout the galaxy and the likelihood of them existing.
For the study, the researchers examined the mixing ratio limits of carbon dioxide, oxygen, and nitrogen to ascertain the type of atmosphere that needs to exist to enable a technological civilization to evolve and survive. While the Earth has a specific ratio of approximately 78 percent nitrogen, 21 percent oxygen, and less than 1 percent carbon dioxide, these ratios might be different on other worlds throughout the galaxy.
The researchers also postulate that plate tectonics play a role in regulating carbon dioxide like Earth, along with the radiation emitted from an exoplanet’s star. In the end, the researchers concluded that not only could ETIs be incredibly rare throughout the galaxy, but that the nearest one is potentially 33,000 light-years from Earth and their lifetimes must be far longer than humans have existed on Earth.
“For ten civilizations to exist at the same time as ours, the average lifetime must be above 10 million years,” said Dr. Manuel Scherf, who is a scientist at the Austrian Academy of Sciences and lead author of the study. “The numbers of ETIs are pretty low and depend strongly upon the lifetime of a civilization.”
What new connections between plate tectonics and ETIs will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: EPSC-DPS2025, EurekAlert!
Featured Image: Artist's illustration of Kepler-168b. (Credit: NASA Ames/NASA/JPL–Caltech/Tim Pyle (Caltech)