Lecture IV: Terrestrial Planets

1
Lecture IV Terrestrial Planets

• From Lecture III Atmospheres
• Earth as a planet interior tectonics.
• Dynamics of the mantle
• Modeling terrestrial planets

2
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
3
Lunar Transit of Earth

• Compare the albedo of the Moon to the Earths
  features, e.g., the Sahara desert.

NASA EPOXI spacecraft (2008)
4
HD 209458b Albedos
New upper limit on Ag
(Rowe et al. 2008)
Rowe et al.(2006)
5
Models Constraints
Different atmospheres
blackbody
model
Equilibrium Temperature
Spitzer Limit
best fit
2004 1 sigma limit or - 2005 3 sigma limit
Rowe et al. 2006 Rowe et al. (in prep)
6
The Close-in Extrasolar Giant Planets
Seager Sasselov 2000

• Type and size of condensate is important
• Possibly large reflected light in the optical
• Thermal emission in the infrared

7
Scattered Light

• Need to consider
• phase function
• multiple scattering

8
Scattering Phase Functions and Polar Plots
MgSiO3 (solid), Al2O3 (dashed), and Fe(s)

Forward throwing glory
Seager, Whitney, Sasselov 2000
9
MOST at a glance
Mission

• Microvariability and Oscillations of STars /
  Microvariabilité et Oscillations STellaire
• First space satellite dedicated to stellar
  seismology
• Small optical telescope ultraprecise
  photometer
• goal
• few ppm few micromag

Canadian Space Agency (CSA)
10
MOST at a glance
Orbit

• circular polar orbit
• altitude h 820 km
• period P 101 min
• inclination i 98.6º
• Sun-synchronous
• stays over terminator
• CVZ 54 wide
• -18º lt Decl. lt 36º
• stars visible for up to 8 wks
• Ground station network
• Toronto, Vancouver, Vienna

11
Lightcurve Model for HD 209458b

• Relative depths
• transit 2
• eclipse 0.005
• Duration
• 3 hours
• Phase changes of planet

Relative Flux
Eclipse
Transit
Phase
12
Lecture IV Terrestrial Planets

• Earth as a planet interior tectonics.
• Dynamics of the mantle
• Modeling terrestrial planets

13
Earths interior
PREM Preliminary Reference Earth Model
14
Earth as a planet - tectonics
15
Earth as a planet - tectonics
16
Earth - plate collision subduction
Evidence from seismic tomography for
the subduction of the plate under Japan.
Variations in shear-wave velocity dvS/vS
Kustowski et al.(2006)
17
Earth - the Core-Mantle Boundary
18
Earth mantle convection simulation
Labrosse Sotin (2002)
19
Earth interior - mantle plumes
20
Earth interior - cooling
21
Super-Earths
22
Super-Earths planets in the mass range
of 1 to 10 ME

• Mass range is now somewhat arbitrary
• Upper range corresponds approx to a core that can
  accrete H2 gas from the disk.
• Two generic families - depending on H2O content.
• No such planets in our Solar System.

(Discussed at Nantes Workshop - June 16-18,
2008)
23
Interiors of Super-Earths
Formation and survival of large terrestrial
planets

All evidence is that they should be around
Ida Lin (2004)
24
The Tree of super-Earths
?
Fe -rich mantle
Terrestrial Planets / Dry, Rocky Planets
?
?
H2O -rich mantle
?
Super-Earths
Ocean Planets / Aqua Planets
?
Mini-Neptunes
25
Super-Earth Model
Input M, Psurf, Tsurf, guess R, gsurf,
composition
Output R, ?(r), P(r), g(r), m(r), phase
transitions, D, ...
26
Interior Modelsthe MassDependence
Zero-temperature spheres Zapolsky Salpeter
(1969) Stevenson (1982) Fortney et al.
(2007) Seager et al. (2007)
(GJ 436b Gillon et al. 2007)
27
Interior Structure of Super-Earths
Valencia, Sasselov, OConnell (2006)
28
Interior Structure Radius Composition
Valencia, Sasselov, OConnell (2007)
29
Phase Diagram of H2O
30
Super-Earths
Confusion region
Mass range 1 - 10 Earth mass
31
Toblerone Diagram
Valencia et al. 2007b
A tool to infer which compositions fit M and R
with uncertainties
32
Degeneracy is important
dRP
Si/Fe 0.6
Si/H2O 0.23
33
Models vs. Kepler observations
Valencia, Sasselov, OConnell (2007)
34
Earth is a perovskite planet

• (Fe, Mg) SiO3
• enstatite
• perovskite (Pv)
• 40 of Earth is Pv !
• post-perovskite (pPv)

Pv pPv at 125 GPa
Tiny amount of post-perovskite at the CMB (the
thin D region)
Super-Earths are post-perovskite planets.
35
Super-Earths as post-Perovskite planets
T-P curves for 7.5 ME models
lt Note all mantles have pressures that reach
1000 GPa
(Valencia, Sasselov, OConnell 2007)
36
Super-Earths very high pressures
37
Post-Perovskite
38
Super-Earths as post-Perovskite planets
Pv
pPv
(Oganov 2006)
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 ?
39
Post- Post-Perovskite ?
Expectation that all (Si, Al, Mg, Fe) oxides
will collapse to an O12 perovskite structure,
like Gd3Ga5O12 (GGG) does at gt120 GPa.
lt above 150 GPa becomes less compressible
than diamond !
(Mashimo, Nellis, et al. 2006)
40
New high-P experiments needed
Z-Beamlet target chamber of 10TWcm-2 setup at
SNL (J.Remo, S.Jacobsen, M.Petaev, DDS)
(2008)
41
T-P Experimental Results
(Remo et al. 2008)
42
We measure 10-50x Fe, Cr, Al -enrichments of the
silicate melts

• Strong mixing occurs due to a Richtmeyer-Meshkov
• instability behind the shock
• - is it scalable relevant to giant impacts
  ?

(Rightley et al. 1996)
43
Interiors of Super-Earths
Valencia, Sasselov, OConnell (2006)
Ocean Planet
Earth-like
44
Interiors of Super-Earths
Mass-Radius relations for 11 different mineral
compositions (Earth-like)

Valencia, OConnell, Sasselov (2005)
1ME 2ME 5ME 10ME
45
Theoretical Error Budget

• Planet Radius Errors
• New high-P phases, e.g. ice-XI -0.4
• EOS extrapolations (V vs. BM) 0.9
• Iron core alloys (Fe vs. FeS) -0.8
• Viscosity, f(T ) vs. const. 0.2
• Overall the uncertainties are below 2
• (at least, thats what is known now)

46
Interior Structure of GJ 876d
20,000
7.5 ME
DENSITY (kg/m3)
12,000
Valencia, Sasselov, OConnell (2006)
4,000
2,000
6,000
10,000
RADIUS (km)
47
Interior Structure of GJ 876d
Valencia, Sasselov, OConnell (2006)
48
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
49
Degeneracy - solution samples
max radius
H2O
min radius
All you need to constrain planet formation
models! - sample with radii to 5 and masses to
10.
50
Dry vs. Ocean super-Earths
Valencia, Sasselov, OConnell (2007)