Scientists unveil new method to find planets that could have life

In a groundbreaking study published in Nature Astronomy, researchers from MIT, the University of Birmingham, and other institutions have introduced a new approach to searching for life beyond Earth.

The key, they say, lies not in what is present in a planet’s atmosphere, but rather in what is missing.

The team, led by Julien de Wit of MIT and Amaury Triaud of the University of Birmingham, suggests that terrestrial planets with significantly lower levels of carbon dioxide compared to their planetary neighbors may harbour liquid water and potentially life.

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This hypothesis is based on observations within our own solar system, where Earth, with its abundant liquid water, has far less atmospheric CO2 than Venus or Mars.

This new method of detecting habitability hinges on the James Webb Space Telescope (JWST), which is capable of identifying the proposed ‘habitability signature’—a relative depletion of carbon dioxide. Unlike previous indicators of habitability that were beyond the capabilities of current technology, this signature can be detected now.

“The Holy Grail in exoplanet science is to look for habitable worlds, and the presence of life,” says de Wit. “Now we have a way to find out if there’s liquid water on another planet. And it’s something we can get to in the next few years.”

The discovery comes after astronomers have catalogued over 5,200 exoplanets, yet direct confirmation of their habitability has remained elusive. While scientists can infer a planet’s potential to support life based on its orbit, direct evidence of liquid water has been unattainable.

The team’s strategy involves first confirming the presence of the atmosphere on these distant worlds by detecting carbon dioxide, then measuring its concentration to identify any significant depletion.

But finding a habitable planet doesn’t necessarily mean it’s inhabited. To address this, the researchers propose looking for ozone in a planet’s atmosphere. On Earth, ozone is a byproduct of life, as oxygen released by plants and microbes reacts with sunlight. If both ozone and reduced carbon dioxide are detected, it could indicate not just a habitable planet, but one teeming with life.

“If we see ozone, chances are pretty high that it’s connected to carbon dioxide being consumed by life,” Triaud explains. “It would be a planetary-scale biomass that’s able to process a huge amount of carbon, and interact with it.”

The JWST is poised to test this theory on systems like TRAPPIST-1, a mere 40 light-years away, where seven Earth-sized planets orbit a single star. This system, among others, could soon reveal whether this new roadmap leads to the discovery of worlds where life as we know it could exist.