What kinds of alien technosignatures should we look for on distant exoplanets? Artificial lighting, pollution, satellite constellations, or something else?
The search for alien life has never been more relevant, and the technologies that are gradually advancing promise much more serious results than anything achieved so far. While biosignatures in distant worlds have always been the main focus of attention, astronomers and enthusiasts around the world have been suggesting an alternative approach – searching for signs of alien technosignatures.
Making our presence known to aliens with technosignatures
More than 200 years ago, scientists proposed that humans should give potential alien civilizations in the Solar System a sign that we exist on Earth. More specifically, we were to make our presence known to aliens on Mars, when the Red Planet was not yet studied and there were assumptions that it could be inhabited.
In the 1800s, scientists had two major plans to indicate our presence. Renowned German Mathematician Carl Friedrich Gauss proposed that people should clear out a massive area in the Siberian forest which would then be planted with wheat in a way that would resemble the Pythagorean Theorem.
This idea was invented in 1802 and of course, such a plantation was never made but 80 years later, astronomer Percival Lovell came out with an even more extraordinary proposal.
He suggested digging deep canals in the Sahara Desert which would then be set afire. He believed that this technosignature would be visible for potential alien civilizations on Mars. Of course, this plan was never followed through either.
Searching for biosignatures
What makes the examples above relevant in the modern-day hunt for alien life?
Exoplanets have been the main focus of attention in recent decades. With several thousand distant exoplanets confirmed to date, astronomers have been trying to identify worlds with biosignatures that suggest the existence of life beyond the Solar System. Scientists search for the presence of gases in exoplanet’s atmospheres in search of worlds that have the same composition as Earth.
While biosignature studies will soon reach new heights with the launch of the James Webb Space Telescope, astronomers have begun considering the search for alien technosignatures as an equally significant alternative.
Searching for alien technosignatures
At this point, the search for technosignatures borders fiction. We do not know what exactly we should look for as we ourselves are the only known example of advanced species in the universe. Yet, the list of potential technosignatures is growing and there are some clever suggestions.
We leave lights aside as this is the most obvious guess. Scientists have proposed alien technosignatures like atmospheric pollution, artificial surface constituents, waste heat from megastructures. And the good thing is that there is no need for separate observations – all this can be found in the same data obtained in biosignature research.
There is one catch, however. In order for us to pick up a signal or a technosignature, this alien civilization should have existed tenths of millions of years ago. Otherwise, the signal wouldn’t have had the time it needs to pass through space to reach us.
Artificial lighting
In the end, artificial lighting remains the most plausible technosignature as any advanced species would produce it. If we take humankind as an example, we could expect that if aliens exist, they also live in cities or at least in groups.
Scientists have investigated the possibility of detecting the “illumination of cities” on distant words and have calculated that it would be possible with space-based telescopes of the near future. The main issue is that scientists used Earth as a model and our planet is not as “heavily” urbanized as an alien world should be for us to detect it.
While only 0.05% of our planet is heavily urbanized (examples are megapolises like Beijing, New York, etc.), alien worlds would be detectable only if the urbanization levels are higher than 10%.
Imagine how much 10% of a planet is when you consider that there are less than 8 billion people on Earth and only 0.05% of our planet is considered as heavily urbanized. The civilization we would find would consist of hundreds of billions of aliens.
Scientists have investigated the possibility of detecting the “illumination of cities” on distant words and have calculated that it would be possible with space-based telescopes of the near future. The main issue is that scientists used Earth as a model and our planet is not as “heavily” urbanized as an alien world should be for us to detect it.
While only 0.05% of our planet is heavily urbanized (examples are megapolises like Beijing, New York, etc.), alien technosignatures would be detectable only if the urbanization levels are higher than 10%.
Imagine how much 10% of a planet is when you consider that there are less than 8 billion people on Earth and only 0.05% of our planet is considered as heavily urbanized. The civilization we would find would consist of hundreds of billions of aliens.
Whatever the possibilities may be, the hunt for alien life is likely to take a while before we find out that we are not alone in this universe. But who knows, maybe someone out there is searching for us like we are searching for them. What if we get a visit first?
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Sources:
• Balbi, A., & Ćirković, M. M. (n.d.). Longevity Is the Key Factor in the Search for Technosignatures. The Astronomical Journal.
• Beatty, T. G. (2021, September 2). The detectability of Nightside City Lights on exoplanets. arXiv.org.
• Kopparapu, R. (n.d.). Nitrogen Dioxide Pollution as a Signature of Extraterrestrial Technology. The Astrophysical Journal.
• Lin, H. W. (n.d.). DETECTING INDUSTRIAL POLLUTION IN THE ATMOSPHERES OF EARTH-LIKE EXOPLANETS. The Astrophysical Journal.
• Physics World. (2021, October 21). Scanning the cosmos for signs of Alien Technology.
