QUANTITATIVELY ASSESSING THE ROLE OF CLOUDS IN THE TRANSMISSION SPECTRUM OF GJ 1214b

By C. Morley, Jon Fortney, Eliza Miller-Ricci Kempton, M. Marley, Channon Vissher, K. Zahnle. 2013

142 citations recorded by the source corpus.

Recent observations of the super-Earth GJ 1214b show that it has a relatively featureless transmission spectrum. One suggestion is that these observations indicate that the planet's atmosphere is vertically compact, perhaps due to a water-rich composition that yields a large mean molecular weight. Another suggestion is that the atmosphere is hydrogen/helium-rich with clouds that obscure predicted absorption features. Previous models that incorporate clouds have included their effect without a strong physical motivation for their existence. Here, we present model atmospheres of GJ 1214b that include physically motivated clouds of two types. We model the clouds that are present in chemical equilibrium, as has been suggested to occur on brown dwarfs, which include KCl and ZnS for this planet. We also include clouds that form as a result of photochemistry, forming a hydrocarbon haze layer. We use a photochemical kinetics model to understand the vertical distribution and available mass of haze-forming molecules. We model both solar and enhanced-metallicity cloudy models and determine the cloud properties necessary to match observations. In enhanced-metallicity atmospheres, we find that the equilibrium clouds can match the observations of GJ 1214b if they are lofted high into the atmosphere and have a low sedimentation efficiency (fsed = 0.1). We find that models with a variety of hydrocarbon haze properties can match the observations. Particle sizes from 0.01 to 0.25 μm can match the transmission spectrum with haze-forming efficiencies as low as 1%–5%.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b6d25a15840b4351250840894a4a8045b7a4b75f

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In Astronomy and Astrophysics

1. Jon Fortney
2. N. Madhusudhan
3. M. Line
4. A. Showman
5. V. Parmentier
6. D. Deming
7. Sara Seager
8. H. Knutson

Citations in the corpus

• WATER VAPOR IN THE SPECTRUM OF THE EXTRASOLAR PLANET HD 189733b. I. THE TRANSIT (2014, methodology): “Fortney et al. (2005) and Morley et al. (2013) show the condensation curves of various species in pressure-temperature phase space.”
• HUBBLE SPACE TELESCOPE NEAR-IR TRANSMISSION SPECTROSCOPY OF THE SUPER-EARTH HD 97658B (2014, background): “If this planet has the same atmospheric composition as GJ 1214b, its modestly higher atmospheric temperature might prevent the formation of the cloud layer detected in GJ 1214b’s atmosphere (Morley et al. 2013).”
• THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA (2015, methodology): “…other atmospheric properties like temperatures and abundances (Ackerman & Marley 2001; Kirpatrick 2005; Cushing et al. 2008; Burrows et al. 2006; Howe & Burrows 2012; Morley et al. 2013;15; Kriedberg et al. 2014a;15; Vahidinia et al. 2014; Knutson et al. 2014; Benneke 2015; Marley & Robinson 2014).”
• BREEDING SUPER-EARTHS AND BIRTHING SUPER-PUFFS IN TRANSITIONAL DISKS (2015, background): “…flat transmission spectra of GJ 3470b, GJ 1214b, and GJ 436b can be attributed to clouds or hazes that form only in environ- ments with supersolar metallicities (e.g., ∼50 × solar; Morley et al. 2013; Crossfield et al. 2013; Biddle et al. 2014; Kreidberg et al. 2014; Knutson et al. 2014).”
• MAKE SUPER-EARTHS, NOT JUPITERS: ACCRETING NEBULAR GAS ONTO SOLID CORES AT 0.1 AU AND BEYOND (2014, background): “On the theoretical side, the supersolar metallicity scenario requires that atmospheres be dusty, but efficient coagulation and sedimentation can clear atmospheres of dust; thus, more studies of cloud/grain physics will also be welcome (Morley et al. 2013; Ormel 2014; Mordasini 2014).”
• UNDERSTANDING THE MASS–RADIUS RELATION FOR SUB-NEPTUNES: RADIUS AS A PROXY FOR COMPOSITION (2013, background): “The atmospheres of Neptune and subNeptune sized planets might be significantly enhanced in metals (Fortney et al. 2013) or host extended clouds that greatly enhance atmospheric opacity (Morley et al. 2013).”
• Transmission spectral properties of clouds for hot Jupiter exoplanets (2014, background): “…on the impact of clouds in exoplanet atmospheres (e.g. Ackerman & Marley 2001; Fortney 2005; Helling 2008; Howe & Burrows 2012; Marley et al. 2013; Morley et al. 2013) and the condensates that are expected in a wide range of temperatures from brown dwarfs to solar system bodies (e.g. Burrows &…”
• A FRAMEWORK FOR CHARACTERIZING THE ATMOSPHERES OF LOW-MASS LOW-DENSITY TRANSITING PLANETS (2013, methodology): “Extremely high mixing ratios of heavy elements will lead to vast reservoirs of material to form thick and opaque clouds (Morley et al. 2013).”
• TRANSITIONS IN THE CLOUD COMPOSITION OF HOT JUPITERS (2016, background): “…their optical properties are more sensitive to physical properties such as the particle size than chemical composition (Heng & Demory 2013) and partly because their vertical distribution is very sensitive to unconstrained processes such as vertical mixing (Morley et al. 2013; Lee et al. 2015).”
• Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report (2015, background): “Even fewer planets in this size range have had their atmospheric properties measured through transit and secondary-eclipse observations (Morley et al. 2013, Caceres et al. 2014) and those spectra are relatively featureless, indicating that high-altitude clouds are veiling the lower atmosphere.”
• HOW TO DISTINGUISH BETWEEN CLOUDY MINI-NEPTUNES AND WATER/VOLATILE-DOMINATED SUPER-EARTHS (2013, background): “…observations of GJ 1214b. KCl and ZnS are considered for GJ 1214b because the he temperature pressure profile in the atmosphere of GJ 1214b is likely to cross their condensation curves, suggesting that KCl and ZnS may be able condense in the atmosphere of GJ 1214b (Morley et al. 2012, 2013).”