Studies of Super-Earth and Terrestrial Planet Atmospheres with JWST

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1 Studies of Super-Earth and Terrestrial Planet Atmospheres with JWST Eliza Kempton (Formerly: Miller-Ricci) Assistant Professor of Physics Grinnell College + University of Maryland, College Park Image Credit: Zach Berta

2 Atmospheric characterization provides a window into the diverse bulk properties of low-mass exoplanets Hadden & Lithwick, AJ, 2017

3 Secondary Atmospheres Imagine the Possibilities... PLANET FORMATION EQUILIBRIUM CHEMISTRY OUTGASSING OF VOLATILES PHOTOCHEMISTRY MASS LOSS COOLING HISTORY CLUSTER ENVIRONMENT PARENT STAR SPECTRUM PLANET LOCATION PLANET TEMPERATURE PLANET SURFACE GRAVITY PLATE TECTONICS PLANET MAGNETIC FIELD

4 Secondary Atmospheres Imagine the Possibilities... PLANET FORMATION EQUILIBRIUM CHEMISTRY OUTGASSING OF VOLATILES PHOTOCHEMISTRY MASS LOSS COOLING HISTORY CLUSTER ENVIRONMENT PARENT STAR SPECTRUM PLANET LOCATION PLANET TEMPERATURE PLANET SURFACE GRAVITY PLATE TECTONICS PLANET MAGNETIC FIELD

5 Observational Results: GJ 1214b GJ 1214 system to scale GJ 1214b 1.4% transit depth GJ 1214b H 2 Planet is too big to be explained without the presence of a significant atmosphere! Lissauer et al., Nature, 2011 (modified c/o E. Lopez)

6 Observational Results: GJ 1214b Solar 30 x Solar 50 x Solar H 2O H2O - CO2 CO2 Transit Depth (%) No atmosphere Wavelength (microns) Miller-Ricci (Kempton) & Fortney, ApJL Mini-Neptune Scenario: Rock / ice interior + hydrogen-dominated atmosphere (mostly H2+ trace H2O, CH4, etc.) 2. Water World Scenario: Mostly H2O - ice/fluid interior + steam atmosphere (i.e. Rogers & Seager, ApJ, Nettelmann et al. 2011)

7 Observational Results: GJ 1214b Featureless spectrum aerosols! Kreidberg et al., Nature 2014 Berta et al., ApJ 2012

8 Observational Results: HD 97658b M pl = 7.9 M R pl = 2.3 R ρ = 3.4 g/cm P = 9.49 days T eq 700 K 3 Inconsistent w/ H2-rich cloud-free composition Knutson et al., ApJ, 2014

9 Observational Results: 55 Cnc e Spitzer phase curve Spitzer secondary eclipse Demory et al., Nature, 2016 Demory et al., ApJL, 2012 variability in dayside emission? Demory et al., MNRAS, 2016

10 Observational Results: TRAPPIST-1 Wang et al., ApJ, submitted DeWit et al., Nature, 2016

11 TESS yields: 100s of potential targets for JWST Sullivan et al., ApJ, 2015

12 Mass measurements are a necessity! Volatile-rich water world, water-rich atmosphere Rocky planet, outgassed H2-rich atmosphere R pl = 1.5 R T obs = 200 hr M4.5 host star (T = 3,000 K, R = 0.2 R ) J = 8 Natasha Batalha, Kempton, & Mbarek, ApJL, 2017

13 Wish List for Super-Earth and Terrestrial Planet Science w/ JWST

14 Identify the division between terrestrial planets and mini-neptunes, as it relates to planet formation and atmospheric evolution (i.e. mass loss) Evaporation valley Lack of Neptune-size planets 0-10 d Lopez, Fortney, & Miller, ApJ, 2012 Owen & Wu, ApJ, submitted

15 Gain a deeper understanding of aerosols in the lowmass planet regime H:O = 1.39 C:O = 0.18 H:O = 2.77 C:O = 0.66 Cloud composition in outgassed super-earth atmospheres H:O = 0.21 C:O = 0.41 H:O = 0.45 C:O = 0.87 Carbon-rich GJ 1214b analogs may host graphite clouds. Mbarek & Kempton, ApJ, 2016

16 Gain a deeper understanding of aerosols in the lowmass planet regime Carbon-Bearing Species CH4 photolysis formation of complex hydrocarbons hydrocarbon haze + sulfur hazes? (e.g. Zahnle et al. (2016), Gao et al. (2017)) Miller-Ricci Kempton, Zahnle, Fortney, ApJ Equilibrium Abundances Photochemical Abundances

17 Measure water abundances and tie this to planet formation and the frequency of water-worlds Water-rich super-earths Raymond et al., Icarus, 2006

18 Classify new types of exotic low-mass planets (i.e. lava worlds) Diversity of outgassed atmospheres Schaefer & Fegley, Icarus, 2009 Elkins-Tanton & Seager, ApJ, 2008

19 Classify new types of exotic low-mass planets (i.e. lava worlds) He-dominated atmospheres from diffusion-limited escape Hu et al., ApJ, 2015 Composition of lava-planet atmospheres Ito et al., ApJ, 2015

20 Earth-Sun system Biosignatures?? TRAPPIST planets 1 ppm 0 ppm O3 Kaltenegger et al., IJAsBio, 2012 Proxima Cen b 60 days co-added observations CH4 O3 JWST NIRSpec + MIRI JWST MIRI Kreidberg & Loeb., ApJL, 2016 Barstow et al., MNRAS, 2016

21 Wish List for Super-Earth and Terrestrial Planet Science w/ JWST Identify the division between terrestrial planets and mini-neptunes, as it relates to planet formation and atmospheric evolution (i.e. mass loss) Gain a deeper understanding of aerosols in the lowmass planet regime Measure water abundances and tie this to planet formation and the frequency of water-worlds Classify new types of exotic low-mass planets (i.e. lava worlds) Biosignatures??

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