How the ELT's Spectrograph Could Sniff Out Biosignatures on Other Worlds

• A new study simulates the potential for the Extremely Large Telescope’s (ELT) ANDES instrument to detect biological gases in the atmospheres of nearby exoplanets.
• Researchers analyzed 18 potentially habitable rocky planets, including several from the TRAPPIST-1 system, for signs of carbon dioxide, water vapor, methane, and oxygen.

Key Research Findings

• The study uses a Bayesian cross-correlation function to mitigate noise, a major hurdle for ground-based telescopes observing distant atmospheres.
• Simulation results reveal distinct detectability levels:
  • Water vapor is the easiest molecule to detect, requiring only 10 to 19 transits for planets in the TRAPPIST-1 system.
  • Oxygen is significantly harder to identify, requiring roughly four times as many transits as water.
  • Only 8 out of the 18 surveyed planets yielded a definitive detection of at least one gas within a 100-transit limit.

Limitations and Caveats

• As a simulation, the study assumes ideal conditions that do not fully reflect real-world challenges:
  • It ignores the common presence of clouds and hazes on exoplanets.
  • It assumes an ability to process data to the "photon-noise limit," which is a significant real-world engineering challenge.
  • It excludes external noise from stellar flares and sunspots common on host stars.

Future Capabilities

• The ANDES instrument will also feature an adaptive-optics-assisted integral-field-unit (IFU) in the near-infrared.
• This secondary mode aims to observe reflected light from non-transiting exoplanets, potentially expanding the telescope's target range beyond transit-dependent observations.