The search for extraterrestrial life relies heavily on analyzing the chemical composition of exoplanet atmospheres. If alien scientists were observing Earth, they would look for key biosignatures — such as oxygen, a byproduct of photosynthesis in plants and bacteria. Similarly, astronomers seek life-dependent chemical signals in distant worlds. While the James Webb Space Telescope (JWST) has advanced this search by studying exoplanet atmospheres, scientists still struggle to define determining biosignatures beyond oxygen. A new study suggests that instead of focusing on a single “holy grail” chemical, researchers should examine the dynamic interactions between atmospheric gases, which could reveal even “life as we don’t know it.”
Oxygen is a well-known biosignature, but other gases, like methane, also indicate biological activity. However, methane can also be produced geologically, as seen on Earth. This ambiguity means that relying solely on one gas can lead to false positives. To address this, researchers propose a more sophisticated method: analyzing atmospheric chemistry as an interconnected system rather than isolating individual compounds.
In a recent study, scientists Theresa Fisher, Estelle Janin and Sara Imari Walker advocate for a ‘chemical reaction network (CRN)’ approach. A CRN maps how different compounds interact and transform within an atmosphere. By modeling these networks, researchers can distinguish between biologically produced gases and those formed through abiotic processes. This method could also detect unknown metabolic processes or even technosignatures from advanced civilizations, offering several key benefits: distinguishing life from non-life, detecting unknown biochemistries, identifying technosignatures and eliminating ambiguous signals.
To test this, the team simulated 30,000 Earth-like atmospheres, categorizing them into two groups:
1. Archaean Earth-like worlds — resembling early Earth (2-4 billion years ago), with methane and ammonia-rich atmospheres and minimal oxygen, possibly hosting microbial life.
2. Modern Earth-like worlds — featuring nitrogen-oxygen atmospheres with traces of industrial gases like chlorofluorocarbons (CFCs).
By comparing network properties, they found that CRN analysis could differentiate between biological, geological, and artificial sources of atmospheric gases. For example, methane could originate from microbial life (methanogenesis) or hydrothermal reactions — only a network-based approach could clarify its true source.
As telescopes like JWST gather more atmospheric data, applying CRN analysis could revolutionize the search for life. This method doesn’t just look for individual gases – it examines the entire chemical ecosystem of a planet, offering deeper insights into potential biospheres. Whether studying primitive microbial worlds or advanced civilizations, this systems-level approach provides a more robust framework for detecting life beyond Earth.
For more details, visit “Universe today“.