Humans have been looking up at the night sky and wondering whether there are any other intelligent forms of life out there since our minds could conceive of them. This is why Ancient Aliens exists — and also why we need to level up our extraterrestrial signal detection.
Earthlings have been through it before. From the famous (or infamous) WOW signal to countless other radio signals that have kept SETI scientists running on high-octane coffee all night, we have focused mostly on just one potential way that E.T. could give us a call, except no one was on the other line. If there are aliens, maybe they think no one is out there. Maybe they all live in deep subsurface oceans. Those hypothetical scenarios aside, they may be releasing technosignatures into space that we don't even recognize.
“New and unique opportunities now exist to look for technosignatures (TS) beyond traditional SETI radio searches, motivated by tremendous advances in exoplanet science and observing capabilities in recent years,” said scientist Hector Socar-Navarro, who led a study recently published in Earth and Planetary Astrophysics.
SETI (Search for ExtraTerrestrial Intelligence) has mostly relied on radio signals until now, but there has still been no hard evidence of an artificial radio signal from space. Too many objects in space give them off. Radio galaxies, pulsars and quasars eject the most radio waves, though any cosmic body with a dynamic magnetic field can produce them. Socar-Navarro and his team have now developed twelve mission concepts that could ditch radio waves and instead zero in on technosignatures, or evidence of alien technology. These concepts are further divided into two categories. Some are supposed to keep an eye on anything weird in the solar system, while others extend to exoplanets.
Something measurable is needed to back what these potential missions will look for if they take off. The ichnoscale was created by Socar-Navarro to see how a signal from another planet measures up to the closest possible signal going out from Earth. For example, if aliens built an enormous spaceship that emitted a stronger signal than the ISS, which is the largest structure we have orbiting our planet, that technosignature would be translated to Earth tech terms by taking the size of the ship’s cross-section and dividing it by the size of the ISS. That would give observers on terra firma a better idea of what to expect from how many times stronger the signal is.
There are many types of technosignatures that could be transmitted through space, from simple to sci-fi level, so each mission will seek out the types that fall within a certain level. One mission concept will be able to pick up on industrial pollution in the atmosphere of an alien planet. This can be an assist to the James Webb Space Telescope, which will be able to detect nitrogen dioxide, which is a commonly found in industrial emissions on Earth.
The question is how close a hypothetical civilization is to life as we know it — and technology as we know it. Aliens may have spawned on a planet with an atmosphere and chemical composition so different from ours, and may have figured out ways of doing things in ways that are unique to their species and environment. Their industrial processes might even go the other way around. What we see as pollutants might be seen as useful to them, and we may not recognize what they see as pollutants to be a sign of industrial activity. Then there could be civilizations so advanced that they have figured out how to avoid pollution to begin with.
It is possible that the same things we consider pollutants may give away a civilization as technologically advanced as we are. We just need to be prepared for technosignatures our Earthling brains may have never imagined.