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The pale orange dot: the spectrum and habitability of hazy Archean Earth

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The pale orange dot : the spectrum and habitability of hazy Archean Earth. / Arney, Giada; Domagal-Goldman, Shawn D.; Meadows, Victoria S.; Wolf, Eric T.; Schwieterman, Edward; Charnay, Benjamin; Claire, Mark; Hébrard, Eric; Trainer, Melissa G.

In: Astrobiology, Vol. 16, No. 11, 01.11.2016, p. 873-899.

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Arney, G, Domagal-Goldman, SD, Meadows, VS, Wolf, ET, Schwieterman, E, Charnay, B, Claire, M, Hébrard, E & Trainer, MG 2016, 'The pale orange dot: the spectrum and habitability of hazy Archean Earth' Astrobiology, vol. 16, no. 11, pp. 873-899. https://doi.org/10.1089/ast.2015.1422

APA

Arney, G., Domagal-Goldman, S. D., Meadows, V. S., Wolf, E. T., Schwieterman, E., Charnay, B., ... Trainer, M. G. (2016). The pale orange dot: the spectrum and habitability of hazy Archean Earth. Astrobiology, 16(11), 873-899. https://doi.org/10.1089/ast.2015.1422

Vancouver

Arney G, Domagal-Goldman SD, Meadows VS, Wolf ET, Schwieterman E, Charnay B et al. The pale orange dot: the spectrum and habitability of hazy Archean Earth. Astrobiology. 2016 Nov 1;16(11):873-899. https://doi.org/10.1089/ast.2015.1422

Author

Arney, Giada ; Domagal-Goldman, Shawn D. ; Meadows, Victoria S. ; Wolf, Eric T. ; Schwieterman, Edward ; Charnay, Benjamin ; Claire, Mark ; Hébrard, Eric ; Trainer, Melissa G. / The pale orange dot : the spectrum and habitability of hazy Archean Earth. In: Astrobiology. 2016 ; Vol. 16, No. 11. pp. 873-899.

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@article{188628a6c1c64d08849ae1dd29a6b9d9,
title = "The pale orange dot: the spectrum and habitability of hazy Archean Earth",
abstract = "Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8–2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97{\%} compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7–2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets.",
keywords = "Haze, Archean Earth, Exoplanets, Spectra, Biosignatures, Planetary habitability",
author = "Giada Arney and Domagal-Goldman, {Shawn D.} and Meadows, {Victoria S.} and Wolf, {Eric T.} and Edward Schwieterman and Benjamin Charnay and Mark Claire and Eric H{\'e}brard and Trainer, {Melissa G.}",
year = "2016",
month = "11",
day = "1",
doi = "10.1089/ast.2015.1422",
language = "English",
volume = "16",
pages = "873--899",
journal = "Astrobiology",
issn = "1531-1074",
publisher = "Mary Ann Liebert Inc.",
number = "11",

}

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TY - JOUR

T1 - The pale orange dot

T2 - Astrobiology

AU - Arney, Giada

AU - Domagal-Goldman, Shawn D.

AU - Meadows, Victoria S.

AU - Wolf, Eric T.

AU - Schwieterman, Edward

AU - Charnay, Benjamin

AU - Claire, Mark

AU - Hébrard, Eric

AU - Trainer, Melissa G.

PY - 2016/11/1

Y1 - 2016/11/1

N2 - Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8–2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7–2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets.

AB - Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8–2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7–2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets.

KW - Haze

KW - Archean Earth

KW - Exoplanets

KW - Spectra

KW - Biosignatures

KW - Planetary habitability

U2 - 10.1089/ast.2015.1422

DO - 10.1089/ast.2015.1422

M3 - Article

VL - 16

SP - 873

EP - 899

JO - Astrobiology

JF - Astrobiology

SN - 1531-1074

IS - 11

ER -

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ID: 248193166