HYDROGEN GREENHOUSE PLANETS BEYOND THE HABITABLE ZONE

By R. Pierrehumbert, E. Gaidos. 2011

220 citations recorded by the source corpus.

We show that collision-induced absorption allows molecular hydrogen to act as an incondensible greenhouse gas and that bars or tens of bars of primordial H2–He mixtures can maintain surface temperatures above the freezing point of water well beyond the “classical” habitable zone defined for CO2 greenhouse atmospheres. Using a one-dimensional radiative–convective model, we find that 40 bars of pure H2 on a three Earth-mass planet can maintain a surface temperature of 280 K out to 1.5 AU from an early-type M dwarf star and 10 AU from a G-type star. Neglecting the effects of clouds and of gaseous absorbers besides H2, the flux at the surface would be sufficient for photosynthesis by cyanobacteria (in the G star case) or anoxygenic phototrophs (in the M star case). We argue that primordial atmospheres of one to several hundred bars of H2–He are possible and use a model of hydrogen escape to show that such atmospheres are likely to persist further than 1.5 AU from M stars, and 2 AU from G stars, assuming these planets have protecting magnetic fields. We predict that the microlensing planet OGLE-05-390Lb could have retained an H2–He atmosphere and be habitable at ∼2.6 AU from its host M star.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8e28074aa2e2fd9f4fe3b7f758e37039d2b6b530

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In Astronomy and Astrophysics

1. D. Charbonneau
2. C. Dressing
3. Timothy Morton
4. E. Gaidos
5. L. Kaltenegger
6. J. Johnson
7. J. Winn
8. Jon Fortney

Citations in the corpus

• THE OCCURRENCE OF POTENTIALLY HABITABLE PLANETS ORBITING M DWARFS ESTIMATED FROM THE FULL KEPLER DATASET AND AN EMPIRICAL MEASUREMENT OF THE DETECTION SENSITIVITY (2015, background): “We do not provide an estimate based on the hydrogen atmosphere HZ of Pierrehumbert & Gaidos (2011) because our search completeness is very low at the maximum allowed separation of 2.4 AU.”
• Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, background): “…formation and migration history, tidal locking of the orbits, space weather, and other factors (see e.g. Huang 1959; Kasting et al. 1993; Pierrehumbert & Gaidos 2011; Kopparapu et al. 2013; Cullum et al. 2014; Kasting et al. 2014; Kopparapu et al. 2014; Ramirez & Kaltenegger 2014;…”
• Origin and evolution of the atmospheres of early Venus, Earth and Mars (2018, background): “In such a case the dense Venus CO2 atmosphere doesn’t result from an initial episode of runaway (or moist) greenhouse, but has been formed during the crystallization of the magma ocean, by progressive exsolution of carbon dioxide, at a time when the atmospheric partial pressure of water and hydrogen”
• The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up (2017, background): “…in the traditional Earth-analog habitable-zone calculation, e.g., greenhouse warming due to elevated levels of atmospheric H2 (Stevenson 1999; Pierrehumbert & Gaidos 2011; Wordsworth & Pierrehumbert 2013; Wordsworth et al. 2017; Ramirez & Kaltenegger 2017), liquid water will freeze at the…”
• Prevalence of Earth-size planets orbiting Sun-like stars (2013, background): “†Pierrehumbert and Gaidos (18) studied the outer edge of the habitable zone.”
• Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs (2017, background): “Several groups have studied the limits of the mainsequence HZ (Kasting et al. 1993; Pierrehumbert & Gaidos 2011; Kopparapu et al. 2013, 2014, 2016; Leconte et al. 2013b; Yang et al. 2013, 2014a; Zsom et al. 2013; Wolf & Toon 2014; Godolt et al. 2015; Leconte et al. 2015; Way et al. 2015; Wolf &…”
• The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “Planets with thick envelopes of H2—an incondensable greenhouse gas—may experience clement conditions for surface liquid water at far lower values of instellation than their counterparts with thick CO2 atmospheres (Pierrehumbert & Gaidos, 2011).”
• Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life (2017, background): “g stable liquid water on the surface. There may be a wide variety of atmospheric compositions that can achieve this result, including N 2,- CO 2,- and H 2-dominated atmospheres (Kasting et al., 1993; Pierrehumbert and Gaidos, 2011; Kopparapu et al., 2013; Seager, 2013; Ramirez and Kaltenegger, 2017)”
• Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model (2017, background): “However, others have suggested that H2 could play a significant role in warming planets at low stellar fluxes (e.g., Pierrehumbert & Gaidos 2011).”
• SPECTRO-THERMOMETRY OF M DWARFS AND THEIR CANDIDATE PLANETS: TOO HOT, TOO COOL, OR JUST RIGHT? (2013, background): “Moreover, these criteria will not apply to planets with a very unEarth-like atmosphere (Pierrehumbert & Gaidos 2011) or much more massive planets where the surface gravity (and hence pressure, for the same optical depth) is much higher.”
• HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: DEPENDENCE ON PLANETARY MASS (2014, background): “The actual outer edge could be further out if additional greenhouse gases (e.g., H2) are present (Pierrehumbert & Gaidos 2011).”
• Transient reducing greenhouse warming on early Mars (2016, unknown): “Current definitions of the outer edge of the habitable zone rely on either CO 2 or H 2 and assume that a biosphere would have a detrimental effect on habitability via methanogenic consumption of these gases [e.g., Pierrehumbert and Gaidos , 2011].”
• How to Characterize Habitable Worlds and Signs of Life (2017, background): “Keeping the planets at the same incident stellar flux as that in our Solar System, Figure 7 shows how the planet–to–star flux ratio changes for a cool M0 host star.”
• Outgassing History and Escape of the Martian Atmosphere and Water Inventory (2015, background): “Depending on the amount and the lifetime of accumulated nebula gas and its evaporation time, a combination of a possible H2 greenhouse (Pierrehumbert and Gaidos 2011; Wordsworth 2012) and the outgassed greenhouse gases may have provided warm and wet conditions on the martian surface for a few tens…”
• Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets (2017, background): “• H2, through Collision Induced Absorptions, is an extremely powerful greenhouse gas that could potentially warm the surface of TRAPPIST-1h well above the melting point of water (Stevenson 1999; Pierrehumbert & Gaidos 2011; Luger et al. 2017).”