Cooke, GJ, Marsh, DR orcid.org/0000-0001-6699-494X, Walsh, C orcid.org/0000-0001-6078-786X et al. (2 more authors) (2023) Variability due to climate and chemistry in observations of oxygenated Earth-analogue exoplanets. Monthly Notices of the Royal Astronomical Society, 518 (1). pp. 206-219. ISSN 0035-8711
Abstract
The Great Oxidation Event was a period during which Earth’s atmospheric oxygen (O2) concentrations increased from ∼10−5 times its present atmospheric level (PAL) to near modern levels, marking the start of the Proterozoic geological eon 2.4 billion years ago. Using WACCM6, an Earth System Model, we simulate the atmosphere of Earth-analogue exoplanets with O2 mixing ratios between 0.1 and 150 per cent PAL. Using these simulations, we calculate the reflection spectra over multiple orbits using the Planetary Spectrum Generator. We highlight how observer angle, albedo, chemistry, and clouds affect the simulated observations. We show that inter-annual climate variations, as well short-term variations due to clouds, can be observed in our simulated atmospheres with a telescope concept such as LUVOIR or HabEx. Annual variability and seasonal variability can change the planet’s reflected flux (including the reflected flux of key spectral features such as O2 and H2O) by up to factors of 5 and 20, respectively, for the same orbital phase. This variability is best observed with a high-throughput coronagraph. For example, HabEx (4 m) with a starshade performs up to a factor of two times better than a LUVOIR B (6 m) style telescope. The variability and signal-to-noise ratio of some spectral features depends non-linearly on atmospheric O2 concentration. This is caused by temperature and chemical column depth variations, as well as generally increased liquid and ice cloud content for atmospheres with O2 concentrations of <1 per cent PAL.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2022. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | astrobiology, planets and satellites: atmospheres, planets and satellites: physical evolution, planets and satellites: terrestrial planets |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Funding Information: | Funder Grant number STFC (Science and Technology Facilities Council) ST/T000287/1 MRC (Medical Research Council) MR/T040726/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 11 Jan 2023 14:41 |
Last Modified: | 25 Jun 2023 23:12 |
Status: | Published |
Publisher: | Oxford University Press (OUP) |
Identification Number: | 10.1093/mnras/stac2604 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:194675 |