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Title: A Volcanic Hydrogen Habitable Zone

Abstract

The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N{sub 2}–CO{sub 2}–H{sub 2}O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO{sub 2} outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H{sub 2} can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N{sub 2}–CO{sub 2}–H{sub 2}O–H{sub 2}) can be sustained as long as volcanic H{sub 2} output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H{sub 2} warming is reduced in dense H{sub 2}O atmospheres. The atmospheric scale heights of suchmore » volcanic H{sub 2} atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.« less

Authors:
;  [1]
  1. Carl Sagan Institute, Cornell University, Ithaca, NY (United States)
Publication Date:
OSTI Identifier:
22654529
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 837; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CAPACITY; CARBON DIOXIDE; CONCENTRATION RATIO; DEGASSING; DETECTION; DIFFUSION; HYDROGEN; PLANETS; SATELLITE ATMOSPHERES; SATELLITES; SCATTERING; SOLAR SYSTEM; STARS; SURFACES; WATER

Citation Formats

Ramirez, Ramses M., and Kaltenegger, Lisa, E-mail: rmr277@cornell.edu. A Volcanic Hydrogen Habitable Zone. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA60C8.
Ramirez, Ramses M., & Kaltenegger, Lisa, E-mail: rmr277@cornell.edu. A Volcanic Hydrogen Habitable Zone. United States. doi:10.3847/2041-8213/AA60C8.
Ramirez, Ramses M., and Kaltenegger, Lisa, E-mail: rmr277@cornell.edu. Wed . "A Volcanic Hydrogen Habitable Zone". United States. doi:10.3847/2041-8213/AA60C8.
@article{osti_22654529,
title = {A Volcanic Hydrogen Habitable Zone},
author = {Ramirez, Ramses M. and Kaltenegger, Lisa, E-mail: rmr277@cornell.edu},
abstractNote = {The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N{sub 2}–CO{sub 2}–H{sub 2}O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO{sub 2} outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H{sub 2} can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N{sub 2}–CO{sub 2}–H{sub 2}O–H{sub 2}) can be sustained as long as volcanic H{sub 2} output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H{sub 2} warming is reduced in dense H{sub 2}O atmospheres. The atmospheric scale heights of such volcanic H{sub 2} atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.},
doi = {10.3847/2041-8213/AA60C8},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 837,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}
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