A collaborative team from the University of Birmingham in the United Kingdom and the Massachusetts Institute of Technology in the United States has introduced a novel method to identify potentially habitable planets by assessing the level of carbon dioxide in their atmospheres. The findings, published in the journal Nature, point to a practical approach for evaluating worlds beyond our solar system and prioritizing targets for future observations.
Habitability is the idea that a celestial body can sustain liquid water on its surface, a condition shaped by distance from its star, atmospheric makeup, and geological activity. Planets that orbit too close to their star risk extreme heat and atmospheric loss, while those too far fall into cold, inhospitable zones where liquid water cannot persist. The concept connects to a broader question of whether a planet can maintain an enduring surface ocean and a climate capable of supporting life as we know it.
The researchers unveiled a new “habitability signature” that could indicate the presence of liquid water on a planet. In the past, scientists gauged potential habitability by studying how a planet reflects starlight from its surface. Now, by measuring atmospheric carbon dioxide levels, scientists can infer whether oceans exist and how they interact with the atmosphere, which in turn raises the odds that life-supporting conditions could occur on the world in question.
The team suggests placing candidate planets beside one another to compare their atmospheric CO2 content with nearby neighbors. If the CO2 concentration declines, it may signal that gas is seeping into the ocean or being absorbed by living biomass across the planet. Such trends could reveal active biogeochemical processes tied to ocean evolution and planetary habitability, offering a more dynamic view than static reflections alone.
Earlier research has explored how microscopic marine life influences climate and ocean chemistry, underscoring the importance of biological processes in shaping planetary environments. In this light, leveraging atmospheric carbon dioxide as a diagnostic tool could complement other methods and help prioritize worlds most likely to harbor oceans and, potentially, life. The collectively advancing knowledge in this field aims to refine the search for life beyond Earth, guiding telescope missions and informing theoretical models about how planets maintain stable, life-supporting conditions over long timescales.