Lecture IV Terrestrial Planets 1 2 3 4

Lecture IV: Terrestrial Planets 1. 2. 3. 4. From Lecture III: Atmospheres Earth as a planet: interior & tectonics. Dynamics of the mantle Modeling terrestrial planets

Observations for Reflected Light • Sudarsky Planet types – I : Ammonia Clouds – II : Water Clouds – III : Clear – IV : Alkali Metal – V : Silicate Clouds • Predicted Albedos: – IV : 0. 03 – V : 0. 50 Picture of class IV planet generated using Celestia Software Sudarsky et al. 2000

Lunar Transit of Earth • Compare the albedo of the Moon to the Earth’s features, e. g. , the Sahara desert. NASA EPOXI spacecraft (2008)

HD 209458 b: Albedos New upper limit on Ag (Rowe et al. 2008) Rowe et al. (2006)

Models Constraints Different atmospheres Equilibrium Temperature blackbody model Spitzer Limit best fit 2004 1 sigma limit – or ~2005 3 sigma limit Rowe et al. 2006 Rowe et al. (in prep)

Seager & Sasselov 2000 The Close-in Extrasolar Giant Planets • Type and size of condensate is important • Possibly large reflected light in the optical • Thermal emission in the infrared

Scattered Light Need to consider: • phase function • multiple scattering

Scattering Phase Functions and Polar Plots Mg. Si. O 3 (solid), Al 2 O 3 (dashed), and Fe(s) Forward throwing & “glory” Seager, Whitney, & Sasselov 2000

MOST at a glance Mission q Microvariability and Oscillations of STars / Microvariabilité et Oscillations STellaire q First space satellite dedicated to stellar seismology q Small optical telescope & ultraprecise photometer q goal: ~few ppm = few micromag Canadian Space Agency (CSA)

MOST at a glance Orbit q circular polar orbit q altitude h = 820 km q period P = 101 min q inclination i = 98. 6º q Sun-synchronous q stays over terminator q CVZ ~ 54° wide q -18º < Decl. < +36º q stars visible for up to 8 wks q Ground station network q Toronto, Vancouver, Vienna CVZ = Continuous Viewing Zone MOST vector l a m r o n orbit to Su n

• Relative depths – transit: 2% – eclipse: 0. 005% • Duration – 3 hours • Phase changes of planet Relative Flux Lightcurve Model for HD 209458 b Eclipse Transit Phase

Lecture IV: Terrestrial Planets 1. Earth as a planet: interior & tectonics. 2. Dynamics of the mantle 3. Modeling terrestrial planets

Earth’s interior PREM = Preliminary Reference Earth Model

Earth as a planet - tectonics

Earth as a planet - tectonics

Evidence from seismic tomography for the subduction of the plate under Japan. Variations in shear-wave velocity: dv. S/v. S Kustowski et al. (2006) Earth - plate collision & subduction

Earth - the Core-Mantle Boundary

Labrosse & Sotin (2002) Earth mantle convection simulation

Earth interior - mantle plumes

Earth interior - cooling

Super-Earths

Super-Earths: planets in the mass range of ~1 to 10 ME 1. Mass range is now somewhat arbitrary • Upper range corresponds approx to a core that can accrete H 2 gas from the disk. 2. Two generic families - depending on H 2 O content. 3. No such planets in our Solar System. (Discussed at Nantes Workshop - June 16 -18, 2008)

Interiors of Super-Earths Formation and survival of large terrestrial planets: All evidence is that they should be around: Ida & Lin (2004)

The “Tree of super-Earths” Super-Earths Terrestrial Planets / Dry, Rocky Planets Fe -rich mantle ? H 2 O -rich mantle Ocean Planets / Aqua Planets Mini-Neptunes ? ? ? ?

Super-Earth Model Input: M, Psurf, Tsurf, guess R, gsurf, composition Output: R, ρ(r), P(r), g(r), m(r), phase transitions, D, . . .

Interior Models: the Mass Dependence Zero-temperature spheres Zapolsky & Salpeter (1969); Stevenson (1982); Fortney et al. (2007); Seager et al. (2007) (GJ 436 b: Gillon et al. 2007)

Valencia, Sasselov, O’Connell (2006) Interior Structure of Super-Earths

Interior Structure: Radius & Composition Valencia, Sasselov, O’Connell (2007)

Phase Diagram of H 2 O

Super-Earths “Confusion region” Mass range: ~1 - 10 Earth mass

‘Toblerone’ Diagram Δ R± R M±ΔM Valencia et al. 2007 b A tool to infer which compositions fit M and R with uncertainties

Degeneracy is important d. R P . 6 0 = e F i/ S Si/H O = 2 0. 23

Valencia, Sasselov, O’Connell (2007) Models vs. Kepler observations

Earth is a ‘perovskite’ planet (Fe, Mg) Si. O 3 - enstatite - perovskite (Pv) 40% of Earth is Pv ! - post-perovskite (p. Pv) Pv p. Pv at ~125 GPa Tiny amount of post-perovskite at the CMB (the thin D” region) Super-Earths are ‘post-perovskite’ planets.

Super-Earths as post-Perovskite planets T-P curves for 7. 5 ME models < Note: all mantles have pressures that reach 1000 GPa (Valencia, Sasselov, O’Connell 2007)

Super-Earths: very high pressures

Post-Perovskite

Super-Earths as post-Perovskite planets p. Pv (Oganov 2006) Pv Does post-perovskite incorporate more Fe ? Is there a post-post perovskite, e. g. like GGG ? Are there analogs to the Pv lower mantle ‘oxygen pump’ ?

Post-Perovskite ? Expectation that all (Si, Al, Mg, Fe) oxides will collapse to an O 12 perovskite structure, like Gd 3 Ga 5 O 12 (GGG) does at >120 GPa. < above 150 GPa becomes less compressible than diamond ! (Mashimo, Nellis, et al. 2006)

New high-P experiments needed (2008) Z-Beamlet target chamber of 10 TWcm-2 setup at SNL (J. Remo, S. Jacobsen, M. Petaev, DDS)

(Remo et al. 2008) T-P: Experimental Results

We measure 10 -50 x Fe, Cr, Al -enrichments of the silicate melts (Rightley et al. 1996) ØStrong mixing occurs due to a Richtmeyer-Meshkov instability behind the shock - is it scalable & relevant to giant impacts ?

Valencia, Sasselov, O’Connell (2006) Interiors of Super-Earths Earth-like Ocean Planet

Interiors of Super-Earths Mass-Radius relations for 11 different mineral compositions (Earth-like): Valencia, O’Connell, Sasselov (2005) 1 ME 2 ME 5 ME 10 ME

Theoretical Error Budget: Planet Radius Errors: Ø Ø New high-P phases, e. g. ice-XI: EOS extrapolations (V vs. BM): Iron core alloys (Fe vs. Fe. S): Viscosity, f(T ) vs. const. : -0. 4% +0. 9% -0. 8% +0. 2% Ø Overall the uncertainties are below 2% (at least, that’s what is known now)

20, 000 7. 5 ME 12, 000 4, 000 2, 000 6, 000 RADIUS (km) 10, 000 Valencia, Sasselov, O’Connell (2006) DENSITY (kg/m 3) Interior Structure of GJ 876 d

Valencia, Sasselov, O’Connell (2006) Interior Structure of GJ 876 d

What would we look for and could we measure it ? Could we measure the difference? - YES: We need at least 5% in Radius, and at least 10% in Mass. Work on tables for use with Kepler underway - masses 0. 4 to 15 ME

Degeneracy - solution: samples s m diu a r ax H 2 O s diu a r in m All you need to constrain planet formation models! - sample with radii to 5% and masses to 10%.

Valencia, Sasselov, O’Connell (2007) Dry vs. Ocean super-Earths