If alien lifeforms on an exoplanet some 40 light-years away had their own version of the James Webb Space Telescope and pointed it at us, would they be able to detect life? The answer is yes, according to a new study dated August 28, 2023, led by astrobiologist Jacob Lustig-Yeager of Johns Hopkins. And it’s the pollution in our atmosphere that gives us away. But the reverse would then also be true. If an alien civilization had technology similar to our own, it might produce pollution in its atmosphere, which we could then spot as a sign of life.
Scientists have considered this idea before. In the new study, the researchers imagined hypothetical aliens on the exoplanet TRAPPIST-1e looking for life on Earth.
Kiona Smith wrote about the latest paper exploring this idea for EuroJournal on September 6, 2023. The paper has not been peer-reviewed or published yet. But you can read a preprint version on arXiv, submitted on August 28.
Simulating Earth as seen from TRAPPIST-1e
The basic premise is that the Webb telescope could possibly find signs of biosignatures or technosignatures on nearby alien worlds. Thus, an advanced alien civilization on one of those planets could potentially find us as well. Seems logical, right? In this scenario, any aliens on TRAPPIST-1e would see Earth as a transiting exoplanet from their location. They could then analyze our atmosphere, just as we study theirs with Webb.
The study focuses largely on the detection of artificially produced pollution in a planet’s atmosphere, such as chlorofluorocarbons (CFCs) on Earth. The study used a new atmospheric data retrieval model called SMARTER. SMARTER is based on previous spectra from terrestrial planets. The paper explained:
This model has the capability to analyze UV to millimeter wave transmission, reflected light and emission data for exoplanets with a wide range of atmospheric compositions, temperatures and pressures.
The researchers used the exoplanet TRAPPIST-1e as an Earth-analog model. It is one of seven Earth-sized rocky planets orbiting the red dwarf star TRAPPIST-1, about 40 light-years away. First, they simulated TRAPPIST-1e data from Webb. They found that Webb should be able to detect molecules from life or technology on TRAPPIST-1e, if they existed. This could include industrial pollutants such as CFCs.
Finding hints of life in messy data
Then the researchers used data from Canada’s SCISAT satellite, which monitors atmospheric gases. They intentionally reduced the data in quality and “made a mess of it.” The idea was to mimic how an alien telescope might see Earth from 40 light-years away. Smith explained how they did this in EuroJournal, saying:
First, the team simulated what SCISAT’s view of Earth’s atmosphere would look like if the satellite were perched at the far edge of our solar system instead of in low-Earth orbit. Next, they added a bunch of ‘noise,’ or random bits of infrared light that don’t come from the star or the planet. Finally, they took samples of this noise-cluttered data at a much lower resolution, similar to how JWST would see a planet 40 light-years away.
And it worked! The researchers were able to detect chemicals in the simulated data associated with life and technology. That they were able to do so even with the messier, lower-quality data was a great achievement. The results showed that indeed, if there were advanced aliens on TRAPPIST-1e with telescopes like Webb, they could find life on Earth. So the reverse should be true as well. For example, if Webb detected CFCs in the atmosphere of TRAPPIST-1e or another exoplanet, that would be very good evidence for a civilization there. On Earth at least, CFCs are only produced artificially.
Is TRAPPIST-1e a habitable exoplanet?
As for TRAPPIST-1e itself, we still don’t know if it can support life of any kind or not. It depends, first of all, on whether the planet has an atmosphere. Webb results for the two closer planets to the star, TRAPPIST-1b and TRAPPIST-1c, have shown that they lack atmospheres or only have extremely thin ones at best. That sounds discouraging.
However, other studies have suggested that TRAPPIST-1e and TRAPPIST-1f may be the most potentially habitable out of all of the seven planets. TRAPPIST-1e may be able to maintain a thicker atmosphere and even water on its surface. But until we have new data from Webb, we just don’t know yet. Webb has been busy looking at several of the TRAPPIST-1 planets, so it might not be too long before we know more about the conditions on TRAPPIST-1e.
Pollution itself isn’t a good thing, of course. But, it may turn out to be one of the first signs of advanced alien life that we ever discover. And it could be one of the first ways that aliens find us. We are just beginning to be able to analyze the atmospheres of planets like TRAPPIST-1e. It will be interesting to see what Webb and other future telescopes find.
Bottom line: Researchers show how an alien civilization on TRAPPIST-1e could find us by detecting our pollution. They simulated Earth as seen from 40 light-years away.
Source: Earth as a Transiting Exoplanet: A Validation of Transmission Spectroscopy and Atmospheric Retrieval Methodologies for Terrestrial Exoplanets
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