Contributed Talk - Splinter Exoplanets

Thursday, 16 September 2021, 17:45   (virtual Exo)

Detectability of biosignatures on LHS 1140 b

Fabian Wunderlich 1, Markus Scheucher 2, John Lee Grenfell 1, Franz Schreier 3, Clara Sousa-Silva 4, Mareike Godolt 5, and Heike Rauer1,6
1: Institut für Planetenforschung, DLR Berlin, Germany (fabian.wunderlich@dlr.de); 2: NASA Jet Propulsion Laboratory, Pasadena, US; 3: Institut für Methodik der Fernerkundung, DLR Oberpfaffenhofen, Germany; 4: Center for Astrophysics, Harvard & Smithsonian, US; 5: Zentrum für Astronomie und Astrophysik, TU Berlin, Germany; 6: Institut für Geologische Wissenschaften, FU Berlin, Germany

Rocky extrasolar planets orbiting M dwarfs are prime targets in the search for habitable surface conditions and biosignatures with near-future telescopes like the James Webb Space Telescope (JWST) and the Extremely Large Telescope (ELT). Even for the closest known targets the capabilities to characterize Earth-like or CO2-dominated atmospheres with JWST or ELT might still be limited to a few molecules such as CO2 or CH4. In clear H2-He atmospheres the detection yields are expected to be much larger. Recent observations of the habitable zone exoplanet LHS 1140 b suggest that the planet might hold a clear H2-dominated atmosphere and might show an absorption feature around 1.4 µm due to H2O or CH4 absorption. In Wunderlich et al. (2021) the detectability of potential biosignatures is investigated, assuming different H2-He atmospheres and varying concentrations of CH4 for LHS 1140 b. For weak abundances of CH4 only five to ten transits are required to detect the potential biosignatures NH3, PH3, CH3Cl, and N2O with JWST or ELT. However, for CH4 surface mixing ratios of a few percent only NH3 and N2O might be detectable with less than 10 transits. A scenario with large abundances of CH4 is consistent with the spectral feature at 1.4 µm and such an atmosphere might allow habitable surface temperatures. If this spectral feature at 1.4 µm originates from H2O absorption, the planet is likely not habitable at the surface.