EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Detectability of biosignatures on LHS 1140 b

Fabian Wunderlich1, Markus Scheucher1, John Lee Grenfell1, Franz Schreier2, Clara Sousa-Silva3, Mareike Godolt4, and Heike Rauer1,5
Fabian Wunderlich et al.
  • 1Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt, Rutherfordstraße 2, 12489 Berlin, Germany (
  • 2Institut für Methodik der Fernerkundung, Deutsches Zentrum für Luft- und Raumfahrt, 82234 Oberpfaffenhofen, Germany
  • 3Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, US
  • 4Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
  • 5Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstr. 74-100, 12249 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. Hence it would be difficult to draw conclusions on the surface conditions and potential habitability of these planets. In clear H2-He atmospheres the molecular features in transmission spectra could be much larger and hence potential biosignatures might be detectable.

In this study, we investigate the detectability of the potential biosignatures NH3, PH3, CH3Cl, and N2O, assuming different H2-He atmospheres for the habitable zone super-Earth LHS 1140 b. Recent observations of the atmosphere of 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. Here we use the coupled convective-climate-photochemistry model 1D-TERRA to simulate H2 atmospheres of LHS 1140 b with different amounts of CH4 and assuming that the planet has an ocean and a biosphere.

The destruction of the potential biosignatures NH3, PH3, CH3Cl, and N2O shows a weak dependence on the concentrations of CH4. For weak abundances of CH4 only 5 to 10 transits are required to detect these molecules 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.

How to cite: Wunderlich, F., Scheucher, M., Grenfell, J. L., Schreier, F., Sousa-Silva, C., Godolt, M., and Rauer, H.: Detectability of biosignatures on LHS 1140 b, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15410,, 2021.

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