The smell of fresh bread unmistakably signals a nearby bakery. But to know if baking is happening right now, it's better to catch not the aroma itself but its intensification — the continuous stream of hot air from the oven. This everyday analogy helps grasp a revolution in the search for extraterrestrial life on exoplanets — planets beyond our solar system. Previous methods were like judging baking only by the concentration of aroma in the room: they measured the total amount of so-called biomarker gases — substances that can be produced by living organisms. The problem is that the same gases can accumulate in the atmosphere over centuries due to purely geological or photochemical processes unrelated to life.

The new approach, proposed by scientists, shifts the focus from concentration to the rate at which gases are released from the planet's surface: their flux. Imagine watching not a stale smell but a jet of hot air from the oven: a continuous hot stream is a sure sign that something is baking inside right now. Similarly in planetary science: by measuring how intensely methane or carbon dioxide enter the atmosphere, one can distinguish fresh emissions from a microbial biosphere from ancient reservoirs long locked in rocks. The analogy, of course, simplifies reality: on planetary scales, fluxes are also affected by ultraviolet destruction of gases and atmospheric reactions, but the key idea, dynamics instead of statics, remains vivid.

The researchers tested this concept on a simulated model of the exoplanet TRAPPIST-1 e, considered a twin of early Earth. A virtual JWST (James Webb Space Telescope) — an instrument capable of obtaining infrared spectra of distant worlds' atmospheres—'captured' spectroscopic fingerprints: unique patterns of light absorption and emission by gas molecules. Then a computer model calculated the fluxes needed to reproduce these spectral features. The analysis confidently revealed the presence of carbon dioxide (CO₂) and methane (CH₄), with the calculated methane flux pointing to a biological source, living producers, with 80% probability, rather than abiogenic processes. It's important to stress: this is not a final diagnosis but a statistically significant hint requiring further observations. We are learning to look not just for frozen traces of life, but for its actual, momentary breath — the continuous exchange of matter between the biosphere and the atmosphere.