Detectability of Atmospheric Climate and Biosignatures with the Large Interferometer for Exoplanets (LIFE) for Terrestrial-type Exoplanets

We investigate the detectability of atmospheric biosignatures with the LIFE mission.

Starting with the modern Earth we model the climate, photochemistry and spectra of Earth-like planets over a range of insolation, gravity, humidity, albedo, atmospheric mass and carbon dioxide abundances and investigate detectability of key atmospheric species by LIFE for Earth-like planets assumed to lie at 10pc for the LIFE (20-day viewing) baseline case. We find that atmospheric ozone (O₃) abundances are maintained over a range of conditions. The O₃ fundamental band is visible for most scenarios studied but is weakened for exoplanets with cooler central stars.

Additional potential biosignatures such as methane (CH₄), nitrous oxide (N₂O) and chloromethane (CH₃Cl) are favored for low UV conditions e.g. exoplanets orbiting cooler central stars or having strong atmospheric shielding. Regarding spectral signatures, CH₄ and water (H₂O) signals from 6-8 μm are evident in most scenarios, as is the carbon dioxide (CO₂) 15 μm band, which strengthens for low-O₂ scenarios associated with upper atmosphere cooling.

Considering the LIFE baseline case with 20-day viewing, H₂O is retrievable with a confidence level (CL) of up to 3σ for the high (90%, 0.9 vmr) CO₂ scenario, and with ∼2σ or less for the other scenarios. N₂O is not be observable with a CL sigma mostly in the range 1-2. CH₄ features a CL sigma detectability range of 2.3-4.4. O₃ is detectable with a CL (>3σ) in most scenarios (including the low-ozone Proterozoic) except for the extremely low O₃ Archaean scenario and the low pressure atmosphere scenario.

Detectability of Atmospheric Climate and Biosignatures with the Large Interferometer for Exoplanets (LIFE) for terrestrial-type Exoplanets, Monthly Notices of the Royal Astronomical Society (open access)

Astrobiology, Astrochemistry, Exoplanet,