The search for inhabited exoplanets has been revolutionized by a new method developed by scientists from the Massachusetts Institute of Technology and the University of Birmingham. This innovative approach involves analyzing the levels of carbon dioxide and ozone in the atmosphere of exoplanets, made possible by modern technologies.
By comparing the low levels of carbon dioxide found in Earth’s atmosphere to the significantly higher concentrations on less inhabited planets like Venus and Mars (with concentrations of 96.5% and 95% respectively), scientists can identify potential signs of planetary habitability. On Earth, the carbon dioxide concentration is a mere 0.04%, thanks to the absorption of about 80% of carbon dioxide by the planet’s oceans.
Building on these findings, the new method focuses on searching for exoplanets with low carbon dioxide levels, which could indicate the presence of large bodies of water. Drawing inspiration from our own solar system, scientists propose looking for planets situated at distances from their host stars that would allow liquid water to exist. If an analysis of the atmosphere reveals a planet with lower carbon dioxide levels, the likelihood of substantial water bodies being present increases.
Of particular interest is the James Webb Space Telescope’s ability to measure carbon dioxide levels on observed planets. “The Holy Grail in the science of exoplanets is the search for inhabited worlds and signs of life,” says Julien de Vit, co-author of the research and assistant professor of planetary sciences at the Massachusetts Institute of Technology. “Now, we have a way to determine if liquid water exists on another planet, and this is something we can pursue in the coming years.”
However, the presence of water does not guarantee the presence of life. Scientists note that on Earth, living organisms including plants and certain microbes consume carbon dioxide and release oxygen, which can then be transformed into ozone through solar photon interaction. Ozone, like carbon dioxide, has a distinct spectral signature that can be detected by the James Webb telescope. Therefore, using this telescope to locate planets within the habitable zone with low carbon dioxide levels and high ozone levels would greatly increase the chances of finding a planet with life.
“If we observe ozone, the probability of it being linked to the consumption of carbon dioxide and therefore life is very high,” explains Amori Trio, co-author of the study from the University of Birmingham. “And if it is indeed life, it would be extraordinary. It wouldn’t just be a few bacteria; it would represent a planetary biomass capable of processing a vast amount of carbon and actively interacting with it.”
The findings of this research were published in the journal