Atmospheric carbon depletion as a tracer of water oceans and biomass on temperate terrestrial exoplanets

Amaury Triaud; Julien de Wit; Frieder Klein; Martin Turbet; Benjamin V. Rackham; Prajwal Niraula; Ana Glidden; Oliver E. Jagoutz; Matej Peč; Janusz j. Petkowski; Sara Seager; Franck Selsis

doi:10.1038/s41550-023-02157-9

Atmospheric carbon depletion as a tracer of water oceans and biomass on temperate terrestrial exoplanets

Amaury Triaud^*, Julien de Wit^*, Frieder Klein, Martin Turbet, Benjamin V. Rackham, Prajwal Niraula, Ana Glidden, Oliver E. Jagoutz, Matej Peč, Janusz j. Petkowski, Sara Seager, Franck Selsis

^*Corresponding author for this work

Physics and Astronomy

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Abstract

The conventional observables to identify a habitable or inhabited environment in exoplanets, such as an ocean glint or abundant atmospheric O2, will be challenging to detect with present or upcoming observatories. Here we suggest a new signature. A low carbon abundance in the atmosphere of a temperate rocky planet, relative to other planets of the same system, traces the presence of a substantial amount of liquid water, plate tectonics and/or biomass. Here we show that JWST can already perform such a search in some selected systems such as TRAPPIST-1 via the CO2 band at 4.3 μm, which falls in a spectral sweet spot where the overall noise budget and the effect of cloud and/or hazes are optimal. We propose a three-step strategy for transiting exoplanets: detection of an atmosphere around temperate terrestrial planets in about 10 transits for the most favourable systems; assessment of atmospheric carbon depletion in about 40 transits; and measurements of O3 abundance to disentangle between a water- versus biomass-supported carbon depletion in about 100 transits. The concept of carbon depletion as a signature for habitability is also applicable for next-generation direct-imaging telescopes.

Original language	English
Number of pages	13
Journal	Nature Astronomy
Early online date	28 Dec 2023
DOIs	https://doi.org/10.1038/s41550-023-02157-9
Publication status	E-pub ahead of print - 28 Dec 2023

Bibliographical note

Acknowledgements
We thank M. Gillon and A. Babbin for insightful discussions. B.V.R. thanks the Heising-Simons Foundation for support. A.H.M.J.T.’s research received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation programme (grant agreement number 803193/BEBOP).

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Cite this

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title = "Atmospheric carbon depletion as a tracer of water oceans and biomass on temperate terrestrial exoplanets",

abstract = "The conventional observables to identify a habitable or inhabited environment in exoplanets, such as an ocean glint or abundant atmospheric O2, will be challenging to detect with present or upcoming observatories. Here we suggest a new signature. A low carbon abundance in the atmosphere of a temperate rocky planet, relative to other planets of the same system, traces the presence of a substantial amount of liquid water, plate tectonics and/or biomass. Here we show that JWST can already perform such a search in some selected systems such as TRAPPIST-1 via the CO2 band at 4.3 μm, which falls in a spectral sweet spot where the overall noise budget and the effect of cloud and/or hazes are optimal. We propose a three-step strategy for transiting exoplanets: detection of an atmosphere around temperate terrestrial planets in about 10 transits for the most favourable systems; assessment of atmospheric carbon depletion in about 40 transits; and measurements of O3 abundance to disentangle between a water- versus biomass-supported carbon depletion in about 100 transits. The concept of carbon depletion as a signature for habitability is also applicable for next-generation direct-imaging telescopes.",

author = "Amaury Triaud and {de Wit}, Julien and Frieder Klein and Martin Turbet and Rackham, {Benjamin V.} and Prajwal Niraula and Ana Glidden and Jagoutz, {Oliver E.} and Matej Pe{\v c} and Petkowski, {Janusz j.} and Sara Seager and Franck Selsis",

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AU - Triaud, Amaury

AU - de Wit, Julien

AU - Klein, Frieder

AU - Turbet, Martin

AU - Rackham, Benjamin V.

AU - Niraula, Prajwal

AU - Glidden, Ana

AU - Jagoutz, Oliver E.

AU - Peč, Matej

AU - Petkowski, Janusz j.

AU - Seager, Sara

AU - Selsis, Franck

N1 - Acknowledgements We thank M. Gillon and A. Babbin for insightful discussions. B.V.R. thanks the Heising-Simons Foundation for support. A.H.M.J.T.’s research received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation programme (grant agreement number 803193/BEBOP).

PY - 2023/12/28

Y1 - 2023/12/28

N2 - The conventional observables to identify a habitable or inhabited environment in exoplanets, such as an ocean glint or abundant atmospheric O2, will be challenging to detect with present or upcoming observatories. Here we suggest a new signature. A low carbon abundance in the atmosphere of a temperate rocky planet, relative to other planets of the same system, traces the presence of a substantial amount of liquid water, plate tectonics and/or biomass. Here we show that JWST can already perform such a search in some selected systems such as TRAPPIST-1 via the CO2 band at 4.3 μm, which falls in a spectral sweet spot where the overall noise budget and the effect of cloud and/or hazes are optimal. We propose a three-step strategy for transiting exoplanets: detection of an atmosphere around temperate terrestrial planets in about 10 transits for the most favourable systems; assessment of atmospheric carbon depletion in about 40 transits; and measurements of O3 abundance to disentangle between a water- versus biomass-supported carbon depletion in about 100 transits. The concept of carbon depletion as a signature for habitability is also applicable for next-generation direct-imaging telescopes.

AB - The conventional observables to identify a habitable or inhabited environment in exoplanets, such as an ocean glint or abundant atmospheric O2, will be challenging to detect with present or upcoming observatories. Here we suggest a new signature. A low carbon abundance in the atmosphere of a temperate rocky planet, relative to other planets of the same system, traces the presence of a substantial amount of liquid water, plate tectonics and/or biomass. Here we show that JWST can already perform such a search in some selected systems such as TRAPPIST-1 via the CO2 band at 4.3 μm, which falls in a spectral sweet spot where the overall noise budget and the effect of cloud and/or hazes are optimal. We propose a three-step strategy for transiting exoplanets: detection of an atmosphere around temperate terrestrial planets in about 10 transits for the most favourable systems; assessment of atmospheric carbon depletion in about 40 transits; and measurements of O3 abundance to disentangle between a water- versus biomass-supported carbon depletion in about 100 transits. The concept of carbon depletion as a signature for habitability is also applicable for next-generation direct-imaging telescopes.

U2 - 10.1038/s41550-023-02157-9

DO - 10.1038/s41550-023-02157-9

M3 - Article

SN - 2397-3366

JO - Nature Astronomy

JF - Nature Astronomy

ER -

Atmospheric carbon depletion as a tracer of water oceans and biomass on temperate terrestrial exoplanets

Abstract

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