cosmic lookout

How scientists will hunt for signs of alien civilizations

If a civilization develops on another planet, it will likely emit these telltale signs.

Originally Published: 
Singapore, September 6, 2020: View at the spectacular red waterfall inside the Changi Airport in Sin...
tobiasjo/iStock Unreleased/Getty Images

Humanity’s search for life beyond Earth has in recent years moved beyond radio, and toward looking for bigger technological achievements, often called technosignatures. While we’ve looked back at our own technological advances for inspiration, Ravi Kopparapu, a researcher at NASA’s Goddard Spaceflight Center, says that may be missing things happening right under our nose.

“We may be trying to find the technosignature that we want to find because that is our imagination,” Kopparapu tells Inverse. “But then the technosignature may be manifesting in a way that's already detectable.”

While interest in the Search for Extraterrestrial Intelligence (SETI) has swelled, and more scientists than ever are hunting for extraterrestrial civilizations, the field remains small and mostly funded by private entities.

Kopparapu is a coauthor on a new paper that breaks down the best ways to look for technosignatures and advocates for more observation time dedicated to resolving one of astronomy’s most pressing questions: Did life develop on another planet?

The paper was published in the May issue of the journal Acta Astronautica.

An artist’s illustration of what an alien megastructure might look like.

Kevin Gill/Flickr, CC BY-SA

What are technosignatures?

Scientists searching for life beyond Earth look for habitable environments on other planets or biosignatures — certain chemicals that may have been produced by some form of past or present life, be it microbes or alien fish.

SETI scientists look less for biospheres and biosignatures, and instead narrowly focus on the hunt for intelligent life. In their models, life was born, survived, and thrived into an advanced civilization much like ours. After all, right now, we’re the only advanced civilization we know about.

So to find technologically advanced civilization, we look for their technological fingerprint in space. Technosignatures like that could come in many different forms.

  • Radio signals in narrowband frequencies: those are radio transmissions not from natural sources. These could be, say, stray astro-Beyonce-like radio tunes or beacons intentionally pointed toward us. Various SETI programs have been performing these observations since 1960.
  • Bright laser flashes: a way for society to announce its presence through interplanetary beacons. This is called Optical SETI or LaserSETI and small-scale observations have been made on it.
  • Megastructures: similar to large solar power plants. While Boyajian’s Star is one of the most famous examples of hunts for megastructures, observations for Dyson Swarm-like objects stretch back to at least 1980.
  • Particle colliders: if an alien civilization exists, they would also want to understand the laws of physics and build huge particle accelerators, possibly using black holes in some form. We might be able to detect them by “pollution” they give off.
  • Pollutants: pollutants emitted from burning fossil fuels. The James Webb Space Telescope will be able to characterize exoplanet atmospheres — and if something is unnatural there, it could be alien smog emissions.
  • An extinction-level event: the gamma rays from a civilization’s extinction.

Wael Farah, a researcher in radio astronomy at the SETI Institute, compares many of these to leakages from radio and television stations that we have on Earth.

“In some ways it leaks outside the Earth,” Farah tells Inverse. “So, we might be able to detect a similar leakage from an extraterrestrial civilization.”

When a planet passes in front of its star from our point of view, we might be able to detect information about its atmosphere — including pollutants.


Future missions to hunt for alien civilizations

In the recent paper, the authors suggest that the search for technosignatures can be tagged onto ongoing and future missions, advocating for time allocation for SETI observations.

With the upcoming launch of the James Webb Space Telescope slated for October 31, 2021, astronomers are anticipating a much more detailed analysis of the composition of the atmosphere of Earth-like, rocky planets.

The telescope could look for gases that would be emitted from the use of technology on another planet.

One possibility is chlorofluorocarbons, a family of chemicals used in the production of aerosol sprays, foams, or air conditioners. Chlorofluorocarbons are not produced naturally.

Webb could also be used for other optical SETI efforts. For instance, looking for infrared heat coming from alien megastructures, or looking for light beacons.

Other missions that will directly observe exoplanets could also provide unprecedented data that could be mined for possible signs of technology, according to the paper.

“A single mission should be able to do multiple things,” Kopparapu says. “We don't need a separate observation time ff we are looking for atmospheric technosignatures, we can just do them simultaneously while doing other observations.”

A NASA illustration for the Manned Lunar Observatory, a concept which included a radio observatory.


Looking for aliens from the Moon

Another idea suggested by the paper is a bit more far-out, literally.

The authors suggest building a radio observatory on the far side of the Moon to search for radio transmissions originating from extraterrestrial technology. Scientists are interested in the far side of the Moon, which constantly points away from Earth, because it is nearly free of contamination from radio emissions being emitted by our radio stations, military outposts, aircraft communication, and whatever else we blast in the radio spectrum.

But for this field of study to get enough funding to launch a project of this scale might take some time.

“The major efforts I would say right now are being funded by private donors,” Farah says. Space agencies are interested in building a base on the Moon, but building a radio observatory would require sending up the different pieces through back and forth space transport, and that costs a lot of money.

It costs $10,000 to put a pound of payload in Earth orbit, according to NASA.

NASA’s High-Resolution Microwave Survey was meant to scan 10 million frequencies using radio telescopes with a funding cost of less than 0.1% of NASA’s total budget. However, Nevada Senator Richard Bryan ensured that it was shut down in 1993.

Since then, NASA was hesitant about putting money towards finding SETI efforts. But recently, the space agency has changed its tune, awarding small funding opportunities towards the hunt for aliens.

“I hope things change in the next few years when we understand that this is one of the most interesting questions scientifically,” Farah adds. “And hopefully we can get more funding.”

This article was originally published on

Related Tags