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Detectability of biosignatures in nearby terrestrial exoplanetary atmospheres with the ELT

Corporaal, Akke (2019) Detectability of biosignatures in nearby terrestrial exoplanetary atmospheres with the ELT. Master's Thesis / Essay, Astronomy.


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Biosignatures, features in planetary atmospheres that can be related to life and may be detected remotely in atmospheres of potential habitable planets, play a key role in our current search for life beyond Earth. Using the knowledge of life to create these signatures, the possible abiotic origin and the sources and sinks in the atmosphere of these signatures, it can be deduced whether a planet may host life. Moreover, for characterisation of atmospheres, the concept of the habitable zone (HZ), the shell around a star where the planetary temperature could be such that liquid water could exist on the surface of a terrestrial planet, was used. Planets located in this region around the host star have preference in future studies related to the search of life beyond Earth. In this thesis it was investi- gated whether frequently proposed biosignatures gases oxygen (O2), ozone (O3), nitrous oxide (N2O), methane (CH4), ethane (C2H6), ammonia (NH3), and methyl chloride (CH3Cl) are detectable with planned instruments for the Extremely Large Telescope (ELT). We included the detectability of the habitability marker water (H 2 O) in our analysis. This was realised by building atmospheres using the exoplanet modelling code ’ARtful Modelling code for exoplanet Science’ (ARCiS) written by Michiel Min. Synthetic spectra for potentially inhabited planets are created using opacity tables at the high resolutions at which the instruments for the ELT will operate. Synthetic reflection- and transmission spectra for the Mid-infrared E-ELT Imager and Spectrograph (METIS) and the High Resolution Spectrograph (HIRES) respectively are created assuming clear atmospheres. For investigating the detectability of biosignatures, the transmission of the atmosphere of the Earth is considered. We consider a hypothetical Earth-Sun analogue at 10 pc, Trappist-1 d, Trappist-1 e, Trappist-1 f, Trappist-1 g, LHS 1140 b, and K2-18 b as examples. It was concluded that METIS may be able to detect the O 3 3.6 μm band, the N 2 O 3.7 μm band and H 2 O features in the wavelength range of 3.5-4.3 μm within 27 observation nights for Earth at 10 pc, Trappist-1 d, Trappist-1 e, Trappist-1 f, and Trappist-1 g. The other spectral features in the mid-infrared will be blocked by Earth’s atmosphere. For the wavelength range of HIRES, the optical and near-infrared, it was concluded that features will not be detectable.

Item Type: Thesis (Master's Thesis / Essay)
Supervisor nameSupervisor E mail
Tak, F.F.S. van
Degree programme: Astronomy
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 27 Aug 2019
Last Modified: 28 Aug 2019 08:13

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