THREE POSSIBLE ORIGINS FOR THE GAS LAYER ON GJ 1214b

By Leslie A. Rogers, Sara Seager. 2009

175 citations recorded by the source corpus.

We present an analysis of the bulk composition of the MEarth transiting super-Earth exoplanet GJ 1214b using planet interior structure models. We consider three possible origins for the gas layer on GJ 1214b: direct accretion of gas from the protoplanetary nebula, sublimation of ices, and outgassing from rocky material. Armed only with measurements of the planet mass (Mp = 6.55 ± 0.98 M⊕), radius (Rp = 2.678 ± 0.13 R⊕), and stellar irradiation level, our main conclusion is that we cannot infer a unique composition. A diverse range of planet interiors fits the measured planet properties. Nonetheless, GJ 1214b's relatively low average density (ρp = 1870 ± 400 kg m−3) means that it almost certainly has a significant gas component. Our second major conclusion is that under most conditions we consider GJ 1214b would not have liquid water. Even if the outer envelope is predominantly sublimated water ice, the envelope will likely consist of a super-fluid layer sandwiched between vapor above and plasma (electrically conductive fluid) below at greater depths. In our models, a low intrinsic planet luminosity (≲2TW) is needed for a water envelope on GJ 1214b to pass through the liquid phase.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f21c661571a2146f815939f6a014313c5ab6b1b9

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In Astronomy and Astrophysics

1. Jon Fortney
2. N. Madhusudhan
3. Sara Seager
4. C. Mordasini
5. D. Charbonneau
6. J. Owen
7. M. Marley
8. E. Lopez

Citations in the corpus

• HOW THERMAL EVOLUTION AND MASS-LOSS SCULPT POPULATIONS OF SUPER-EARTHS AND SUB-NEPTUNES: APPLICATION TO THE KEPLER-11 SYSTEM AND BEYOND (2012, background): “In general, there is a large degeneracy between the relative amounts of rock, iron, water, and hydrogen/helium (Rogers & Seager 2010a).”
• Compositional Imprints in Density–Distance–Time: A Rocky Composition for Close-in Low-mass Exoplanets from the Location of the Valley of Evaporation (2017, methodology): “Such combined measurements directly lead to the mean density of the planet which can be used as a first constraint on the bulk composition (e.g., Valencia et al. 2007, 2010; Rogers & Seager 2010b,a).”
• A FRAMEWORK FOR CHARACTERIZING THE ATMOSPHERES OF LOW-MASS LOW-DENSITY TRANSITING PLANETS (2013, background): “This question has really only been extensively investigated for GJ 436b (Nettelmann et al. 2010) and GJ 1214b (Rogers & Seager 2010; Nettelmann et al. 2011; Valencia et al. 2013).”
• MOST 1.6 EARTH-RADIUS PLANETS ARE NOT ROCKY (2014, background): “For planets in this size range, a wide diversity of planet compositions are a priori plausible; rock, astrophysical ices (H2O, NH3, and CO), and H/He gas can all make significant contributions to both the planets’ mass and volume (e.g., Rogers & Seager 2010a,b).”
• BULK COMPOSITION OF GJ 1214b AND OTHER SUB-NEPTUNE EXOPLANETS (2013, methodology): “Previous studies Our maximum content for H/He agrees with both Rogers & Seager (2010b) and Nettelmann et al. (2011) despite having different treatments.”
• THE OPTICAL AND NEAR-INFRARED TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ 1214b: FURTHER EVIDENCE FOR A METAL-RICH ATMOSPHERE (2011, background): “The only thing that can be said with a high degree of confidence based on just the mass and radius of the planet is that it must have a substantial atmosphere because it is too large to be composed solely of solid material (Rogers & Seager 2010b; Nettelmann et al. 2011).”
• Observations of Transiting Exoplanets with the James Webb Space Telescope (JWST) (2014, background): “…there remains fundamental uncertainty as to its nature, either a mini-Neptune composed primarily of a rock/ice interior with a large hydrogen dominated atmosphere and traces of water and methane, or a true “water world” with a predominantly icy interior and an H2O atmosphere (Rogers & Seager 2010).”
• HUBBLE SPACE TELESCOPE NEAR-IR TRANSMISSION SPECTROSCOPY OF THE SUPER-EARTH HD 97658B (2014, background): “…sample it is possible to match their measured densities with a broad range of compositions, including both waterrich and water-poor scenarios, simply by varying the amount of hydrogen in their atmospheres (Seager et al. 2007; Valencia et al. 2007, 2013; Rogers & Seager 2010a; Zeng & Sasselov 2013).”
• MAKE SUPER-EARTHS, NOT JUPITERS: ACCRETING NEBULAR GAS ONTO SOLID CORES AT 0.1 AU AND BEYOND (2014, background): “E P] 4 N ov 2 01 4 2 super-Earths apparently retain only small amounts of gas: only ∼3–10% by mass (e.g., Lopez & Fortney 2014) or even less (e.g., Rogers & Seager 2010a,b), based on modeling of observed radius-mass data.”
• UNDERSTANDING THE MASS–RADIUS RELATION FOR SUB-NEPTUNES: RADIUS AS A PROXY FOR COMPOSITION (2013, methodology): “For 1- 2 R⊕ planets the densities of water, silicate rocks, and iron (i.e. ∼ 1-10 gcm−3) are similar enough that it is impossible to uniquely constrain the relative abundance of these components (Valencia et al. 2007; Rogers & Seager 2010a).”
• Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer (2011, background): “Its large radius (Rp = 2.44 ± 0.21 R⊕, Carter et al. 2011) suggests a significant gaseous envelope that could originate from the outgassing of the rocky/icy surface material of a terrestrial planet or that could be of primordial origin, making it a kind of “mini-Neptune” (Rogers & Seager 2010).”
• TESTING IN SITU ASSEMBLY WITH THE KEPLER PLANET CANDIDATE SAMPLE (2013, background): “This could be the result of gas capture from the nebula or outgassing post-assembly (e.g., Rogers & Seager 2010).”
• PHOTOCHEMISTRY IN TERRESTRIAL EXOPLANET ATMOSPHERES. I. PHOTOCHEMISTRY MODEL AND BENCHMARK CASES (2012, background): “It is also possible that some super-Earth atmospheres are water rich (Rogers & Seager 2010; Bean et al. 2010; Miller-Ricci Kempton et al. 2012).”
• HOW ROCKY ARE THEY? THE COMPOSITION DISTRIBUTION OF KEPLER’S SUB-NEPTUNE PLANET CANDIDATES WITHIN 0.15 AU (2014, background): “Inferring more detailed composition parameters like an individual planet’s core, mantle, and envelope mass is of course a highly degenerate problem made worse by the possible choices for the number and type of layers in the planet’s interior (Valencia et al. 2007; Rogers & Seager 2010).”
• TRANSIT DETECTION IN THE MEarth SURVEY OF NEARBY M DWARFS: BRIDGING THE CLEAN-FIRST, SEARCH-LATER DIVIDE (2012, background): “…size range accessible to atmospheric characterization, GJ1214b has proven a useful laboratory for theoretical work (e.g Miller-Ricci & Fortney 2010; Rogers & Seager 2010; Nettelmann et al. 2011; Menou 2012; Miller-Ricci Kempton et al. 2012) and for observational studies, both from the ground (e.g.…”