Given just how incomprehensibly, unfathomably big the universe is, chances are tiny that Earth is the only planet with life on it. But how would we find others? A new NASA grant has been awarded to aid the search for extraterrestrial intelligence (SETI) by hunting for signs of advanced alien civilizations.
Looking for signs of life beyond Earth is something of a priority for NASA and other space agencies. Most of the time scientists are hunting for natural biosignatures on exoplanets, which would be gases like methane or oxygen that could indicate life – even as simple as microorganisms or plants – is thriving there.
But here on Earth, the most obvious signs of life aren’t natural at all. We’ve been pumping huge amounts of pollutants into the atmosphere for centuries, huge swathes of the planet's surface glitter at night with artificial lights, and we’ve manipulated the terrain and put up gigantic buildings. Even the space around the planet is increasingly clogged with satellites.
So if our civilization leaves these fingerprints – or “technosignatures” – on our home planet, maybe others would too. Detecting them could be a dead giveaway for alien life, and NASA has now funded a study called “Characterizing Atmospheric Technosignatures” that is intended to do just that.
"Technosignatures relate to signatures of advanced alien technologies similar to, or perhaps more sophisticated than, what we possess," says Avi Loeb, a Harvard Professor on the new project. "Such signatures might include industrial pollution of atmospheres, city lights, photovoltaic cells (solar panels), megastructures, or swarms of satellites.”
The team says that the study will initially focus on two of these technosignatures: solar panels and air pollution. Solar panels, for instance, are designed to absorb certain wavelengths of light, while others would be reflected. That could create a specific spectral signature that telescopes could detect when observing exoplanets.
As for pollutants, the team would focus more on artificial gases that don’t really occur in nature. An example is chlorofluorocarbons (CFCs), which we once commonly used as refrigerants and aerosols until it was discovered that they were destroying the ozone layer.
But how can we actually look for these things around planets that are huge distances away from Earth? The new project will characterize what these technosignatures would actually look like in data that will then be collected into an online library that astrophysicists can use to identify exoplanets that may be of interest for follow-up studies.
“Our job is to say, ‘this wavelength band is where you might see certain types of pollutants, this wavelength band is where you would see sunlight reflected off solar panels’,” says Adam Frank, a University of Rochester Professor on the project. “This way astronomers observing a distant exoplanet will know where and what to look for if they’re searching for technosignatures.”
This is the first SETI-specific grant that NASA has awarded in over 30 years, and the very first to search for technosignatures other than radio waves.
