Researchers have proposed a new method for identifying habitable or inhabited environments on exoplanets, suggesting that a low carbon abundance in the atmosphere of a temperate rocky planet could indicate the presence of liquid water, plate tectonics, and/or biomass. This innovative approach, outlined in a recent article published in Nature Astronomy, offers a potential breakthrough in the search for extraterrestrial life.
The conventional observables used to identify habitable conditions on exoplanets, such as an ocean glint or abundant atmospheric O2, are often challenging to detect with current or upcoming observatories. However, the researchers propose that the atmospheric carbon depletion in a temperate rocky planet, relative to other planets in the same system, could serve as a valuable indicator of habitability.
The study highlights the potential of the James Webb Space Telescope (JWST) to conduct such searches in selected systems, such as TRAPPIST-1, utilizing the CO2 band at 4.3 μm. This spectral sweet spot offers optimal conditions for detecting atmospheric carbon depletion, while minimizing the impact of cloud and/or hazes.
The researchers outline a three-step strategy for studying transiting exoplanets, which includes the detection of an atmosphere around temperate terrestrial planets, assessment of atmospheric carbon depletion, and measurements of O3 abundance to distinguish between water- and biomass-supported carbon depletion. The concept of carbon depletion as a signature for habitability is also deemed applicable for next-generation direct-imaging telescopes.
This new approach opens up exciting possibilities for advancing the search for potentially habitable exoplanets and extraterrestrial life. As technology continues to evolve, the prospects for discovering life beyond our solar system are becoming increasingly promising.
