Humans’ “first contact” with aliens is likely to be with a civilization much more technologically advanced than ours, according to a new NASA-funded study into the search for intelligent extraterrestrial life (SETI).
According to the paper published in the specialized journal Acta Astronautica, the easiest way to detect extraterrestrial civilizations is by searching for “technosignatures”—evidence for the use of technology or industrial activity in other parts of the Universe.
Technosignatures, many of which are based on how Earth might look now, or in the past or future, to alien onlookers, include:
- Radio signals, such as the Arecibo message we humans sent in the direction of globular star cluster M13 on November 16, 1974.
- The presence of industrial pollution in the atmosphere of a planet. For example, the presence of nitrogen dioxide—as studied recently by the same team of researchers—or the wholly artificial chlorofluorocarbons (CFCs), both of which are evidence for there being a technologically advanced civilization on Earth.
- Large swarms of satellites around a planet.
- Gigantic space engineering around exoplanets, such as heat shields or “Dyson spheres” that harvest solar energy from the local star.
- Crash sites on the Moon or Mars of probes that might have been sent here in a distant past.
However, the study—which was funded by NASA Goddard’s Sellers Exoplanet Environments Collaboration (SEEC) and the NASA Exobiology program—argues that our search for technosignatures would likely only be successful at finding much more advanced technology than humans can currently create.
That raises the spectre of “contact inequality.”
“It seems unlikely that civilizations with a relatively low level of technological development would enter into contact with each other, since that would require either very high sensitivities or highly visible engineering,” reads the paper. “Less advanced civilizations lack the sensitivity needed to detect other civilizations unless they have built very large or luminous structures.”
In short, we don’t yet have instruments sensitive enough to definitively find “another Earth” by detecting an alien civilization outright.
That’s despite huge advances in our astronomical instrumentation in the past decade that have revolutionized the science of discovery and study of exoplanets, which now number 4,000+.
“For us to detect such signals at interstellar distances with our current sensitivities, such signals would need to be stronger than those produced by current human civilization, particularly the unintentional ones,” read the paper. “Only those species that have constructed or developed technology is much larger or more luminous than any of our own can be detected with our current astronomical infrastructure.”
So we’re looking for massive, unmistakable signs of alien civilisations far more advanced that we are.
“The idea of searching for technosignatures draws upon the technology we have on Earth today and possible extensions of our technology into the future,” said Jacob Haqq-Misra, a co-author of the article and chairman of the TechnoClimes 2020 organizing committee. “This does not necessarily mean that any extraterrestrial technology must be like our own, but imagining plausible extensions of our own future is one place to begin thinking of astronomical searches we could actually do to look for possible technosignatures.”
The study puts forward a plan, and a new way of classifying the technosignatures as a function of their “cosmic footprint”—the relative size scale of a given technosignature in units of the same technosignature produced by current Earth technology. It’s a measure of how easy to see a technosignature might be from a huge distance. The researchers call this an “ichnoscale.”
Scale and scope is tricky since a search for crashed spacecraft on the Moon could easily be done, whereas a search for Dyson spheres in our galaxy would have a billion potential targets, according to the paper.
Don’t get the idea that armies of astronomers and NASA scientists are spending their days and nights searching for traces of extraterrestrial intelligence. They’re not. In fact, the renewed interest in “technosignature science” is largely down to the fact that it can be done purely by taking advantage of data that is already being collected astronomical purposes.
For example, many space telescopes and survey satellites—such as TESS—observe stars to see if exoplanet are transiting across them. That’s exactly the same science that needs to be done to search for technosignatures.
The next generation of telescopes—such as the James Webb Space Telescope (JWST), but many others—will also, for the first time, allow a search for so-called biomarkers, evidence for life on other planets. While characterizing the atmosphere of an exoplanet it will by default detect the presence of, say, CFCs or nitrogen dioxide.
It’s therefore something of a free hit, according to the researchers—the modern search for aliens can be all about synergy.
A free hit it may be, but it could also be a fruitless one. “We have no idea whether intelligence is something very common in the Universe or, on the contrary, whether it is extremely rare,” said Hector Socas-Navarro, an IAC researcher, the Director of the Museum of Science and the Cosmos, of Museums of Tenerife, and the first author of the paper.
“For that reason we cannot know whether these searches have any chance of success. There is no choice but to search and see what we find, because the implications would be tremendous.”
Wishing you clear skies and wide eyes.