The 39-meter diameter ELT represents a quantum leap in observational astronomy. When it begins operations in 2028, it will collect more light than any previous ground-based telescope by an order of magnitude and produce images with resolution surpassing the Hubble Space Telescope by 16 times. This monumental advancement in observational power opens new frontiers in the search for biosignatures – chemical markers that might indicate the presence of life – on worlds beyond our solar system.

Unlike previous studies that focused primarily on transit observations, where planets pass in front of their stars from our vantage point, the new research led by Miles Currie from the University of Washington and NASA Goddard Space Flight Center demonstrates how the ELT could directly analyze light reflected from exoplanet atmospheres. This approach dramatically expands the pool of potential target worlds.

“The upcoming extremely large telescopes will provide the first opportunity to search for signs of habitability and life on non-transiting terrestrial exoplanets using high-contrast, high-resolution instrumentation,” the research team explains. This crucial distinction means astronomers won’t be limited to the small percentage of planetary systems aligned perfectly for transit observations.

The research team conducted sophisticated simulations to determine which atmospheric gases could be detected using the ELT’s advanced instruments. They examined five photochemically self-consistent atmosphere types: modern Earth-like, Archean Earth-like (representing Earth about 2.5 billion years ago), uninhabited “false positive” environments, and a sub-Neptune world.

For each atmosphere type, they determined the detectability of key molecules including oxygen (O₂), methane (CH₄), carbon dioxide (CO₂), water vapor (H₂O), carbon monoxide (CO), and ammonia (NH₃). These gases aren’t chosen randomly – they represent critical markers of planetary conditions that might support life or even indicate its presence directly.

The team’s findings suggest that for the most accessible nearby target, Proxima Centauri b – just 4.2 light-years away – the ELT could rule out a sub-Neptune atmosphere in as little as one hour of observing time. More significantly, two biosignature pairs (O₂/CH₄ and CO₂/CH₄) might be detectable in approximately 10 hours under optimal conditions.