A team of researchers from ETH Zurich and the University of Zurich has recently published a study that could significantly advance our ability to detect extraterrestrial life on exoplanets, with Earth serving as the guinea pig.
Published in The Astrophysical Journal, their work focuses on the Large Interferometer for Exoplanets (LIFE) space mission and its potential to characterize the habitability of exoplanets by observing Earth as a test object.
The Large Interferometer for Exoplanets (LIFE) is a proposed space mission designed to directly measure the mid-infrared spectrum of terrestrial habitable zone exoplanets. Using a collection of small orbiting telescopes, the mission would characterize the atmospheres of these exoplanets, assess their potential habitability, and search for signs of extraterrestrial life beyond our solar system.
With hopes that these space-based telescopes would one day be built, the researchers aimed to validate the LIFE mission’s ability to detect signs of life on exoplanets. Using Earth as a proxy, they proposed simulating how LIFE would observe an exoplanet.
The Subtle Art of Using Earth to Spot Extraterrestrial Life in the Cosmos
The study successfully characterized Earth as if it were an exoplanet using simulated observations of its Mid-Infrared thermal emission spectrum. The research concluded that Earth would be identified as a temperate, habitable planet with detectable levels of important atmospheric gasses such as carbon dioxide (CO2), water vapor (H2O), ozone (O3), and methane (CH4), which are significant for indicating the presence of life and habitable conditions. A good sign, seeing as how our planet is teeming with life (at least for now).
Now, here is where things get interesting. The study also found that the viewing angle and season did not significantly alter the detectability of these molecules or their relative abundances in Earth’s atmosphere. This is important because something as simple as cloud cover can mess with atmospheric data.
Moreover, seasonal changes in the amount of energy Earth reflects or emits were observed, particularly when the North Pole was observed, which led to variations in retrieved surface temperature, equilibrium temperature, and Bond albedo (in simple terms, it is how much electromagnetic radiation that ends up back in space after bouncing off the planet, but not coming from the planet directly). Due to this accuracy, the study was able to figure out Earth’s surface temperature despite the presence of clouds.
Surface pressure was much tougher to sort out, so future work needs to go into developing better methods to properly get those numbers. Basically, due to the scattered nature of Earth’s atmosphere, and by extension, other possible exoplanets like Earth out there, it made it difficult for the instruments to get an accurate reading.
However, there is a silver lining to error.
The research highlighted that common simplifications, such as neglecting clouds and assuming constant vertical gas abundances, introduce biases in the retrieval results. When interpreting exoplanet atmospheric data, including all the data collected up to now by other studies and astronomers, it all may need a second look. Earth is atmospherically complex. What’s to say the other exoplanets we’ve already discovered aren’t as complex?
Using Earth as a test subject provides compelling evidence that the mission’s measurement procedures are feasible and effective. Moreover, it also opens new avenues for the exploration of habitable worlds, marking a pivotal moment in the quest to understand our place in the universe and potentially finding signs of extraterrestrial life.
“The whole exoplanet community is gearing up for increasing amounts of data that will be coming in the future from smaller and smaller planets,” explained Professor Sascha at ETH Zurich Quanz, one of the study’s authors. Since Earth is the only planet with life as we know it, using it to test future equipment makes sense.
MJ Banias is a journalist who covers security and technology. He is the host of The Debrief Weekly Report. You can email MJ at mj@thedebrief.org or follow him on Twitter @mjbanias.