Planetary Atmospheres: From Here to Light-Years Away

Xi Zhang University of Arizona/LPL

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NAOC Jul. 9, 2014

Galileo Galilei (1564-1642)

The Galileo manuscript in UMich library 2  

Before my middle school

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Now

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Before my middle school

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Now

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Atlas of the Universe

Planetary Atmosphere (Matter Energy Motion)

Chemistry

Dynamics Radiation

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•  Is there an atmosphere?

•  What is it made of?

•  How does it move?

•  Too many reasons to be listed here

•  Richness of Information

•  Habitability

•  Origin and Evolution

Why Planetary Atmosphere?

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The dawn of exoplanet discovery has unearthed a rich tapestry of planets different from anything encountered in the Solar System. Geoscientists can and should be in the vanguard of investigating what is out there in the Universe. -Pierrehumbert (2013)

Richness of Information: Diversity

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Origin and Evolution

•  Observation

•  Theory

Outline

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Credit: NASA

Observation

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Venus Exploration

Akatsuki (2010- )!Fingers Crossed!!

Venus Express (2006- )!

Venera-D (2024- )!

Venus Orbiter (2015- )!

Vega Missions

Jupiter Exploration

Pioneer 10 & 11!(1973)!

Voyager I & II!(1979)!

Ulysses!(1992)!

Galileo Orbiter!(1995-2003)!

Credit: NASA, ESA

Juno !(2016- )!

New Horizon !(2007)!

Cassini!(2000/2001)!

Juice !(2030- )!15  

Credit: NASA 16  

VENUSTARGETINGMANEUVER3 DEC 1998

EARTH FLYBY18 AUG 1999

VENUS 2 FLYBY24 JUN 1999

VENUS 1 FLYBY26 APR 1998

LAUNCH15 OCT 1997

JUPITER’S ORBIT

11.8 YEARS

JUPITERFLYBY

30 DEC 2000

SATURN’S ORBIT

29.1 YEARS

SATURN ORBIT INSERTION1 JUL 2004

SUN

Cassini Trajectory

Cassini Configuration

Credit: NASA 17  

Cassini Spectral Coverage

UVIS!

ISS!

VIMS!

CIRS!

           

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100 200 300 400 500 600

120

140

600 700 800 900 1000 1100

Brig

htne

ss Te

mpe

ratu

re (K

)

120

140

Wavenumber (cm -1)1100 1150 1200 1250 1300 1350 1400

120

140

160

Tropospheric Emission

NH 3

StratC 2H2

StratC 2H6

TropNH 3

Stratospheric Emission from CH4

H2S(0)

H2

S(1)

H2S(1)

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CIRS Spectra on Jupiter

-80 -60 -30 0 30 60 800Latitude (Degree)

10000

1000

100

10

Pres

sure

(Pa)

-80 -60 -30 0 30 60 800Latitude (Degree)

-80 -60 -30 0 30 60 800Latitude (Degree)

100

120

140

160

180

200

100.0

10.0

1.0

0.1

Pres

sure

(mba

r)

115115 120120125125130130 135135 140140 145145 150

150155

155160

160

160

165

165

165

165

165

170170

175

Zhang et al. (2013)

CB3MT3UV1

ISS images of Jupiter

0.2 0.4 0.6 0.8 1.0Wavelength (µm)

0.00010.0010

0.0100

0.10001.0000

UV1 MT3 CB3

CH4  O

p/cal  D

epth  

Rayleigh  

Gas+Tropospheric Haze + Semi-infinite Cloud

Stratospheric Haze

Gas (CH4 + Rayleigh)

Gas (CH4 + Rayleigh)

DHG Phase Function (f1, g1, g2)

Effective Cloud Top (Pcld)

Low Latitutdes:CSM Model (CSM Particle)

Middle and High Latitutdes:AGG Model (Aggregated Particle)

Sun Observer

Zhang et al. (2013) 20  

-75 -50 -25 0 250Latitude (Degree)

100

10

1

Pres

sure

(mba

r)

-75 -50 -25 0 250Latitude (Degree)

100

10

1

Pres

sure

(mba

r)

-75 -50 -25 0 250Latitude (Degree)

100

10

1

Pres

sure

(mba

r)

0

0.05

0.1

0.15

0.2

0.25

(0.2-0.5 µm) (~0.01 µm)

~1000

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Faces of Jovian Aerosols

Zhang et al. (2013)

UVIS on Titan

22  Kammer et al. (2013)

Atmosphere on Exoplanets:

What we can observe?

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How do we know it is there?

HR8799 system (129 Ly, Keck, Marois et al.)

Beta Pictoris system (63 Ly, VLT, Lagrange et al.)

Transit

Fomahaut system (25 Ly, HST, Kalas et al.)

Doppler

Imaging

Atmosphere Detection

Atmosphere Detection

Line, Zhang et al. (2012)

Clouds/Hazes

Knutson et al. (2014) for GJ436b Kreidberg et al. (2014) for GJ1214b

Indirectly Detect the Wind

Snellen et al. (2014)

Showman et al. (2013) Snellen et al. (2010)

directly Detect the Wind

•  Observation

•  Theory

Outline

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Planetary Atmosphere (Matter Energy Motion)

Chemistry

Dynamics Radiation

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•  Is there an atmosphere?

•  What is it made of?

•  How does it move?

Minimum Recipe ?

•  Mass

•  Radius

•  Rotation

•  Temperature

•  Boundary Conditions

•  External/Internal Forcing

Composition

Wind Pattern

Climate

Thermochemistry

Moses et al. (2013) Hu et al. (2014)

Dynamics in a Nutshell

34  Credit: Adam Showman

A Simple Framework

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Force-Dissipation System

•  External Forcing

•  Internal Forcing

•  Dissipation (Radiation/turbulences/drag)

External Forcing

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•  Milankovitch Cycle

•  Faint Young Sun

•  Runaway Greenhouse

•  Ice-Albedo Feedback

•  Magnetic Effect

Earth Venus!

Example: What Happened on Venus?

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• Size 6378 km 0.95x Earth

• Mass 6x1024 kg 0.8x Earth

• Density 5.5 g/cm3 0.9x Earth

• Rotation 1 day 186 days

• Orbit 1 AU (1 yr) 0.7 AU (243 d)

• Atmosphere 78% N2 & 21% O2 96.5% CO2 & 3.5% N2

• Temp/Pres. 20°C (1 bar) 467°C (92 bar)

• Liquid water Yes No

• Plate tectonics Yes No

If we move the Earth further away…

Zaliapin & Ghil (2010) Kleidon (2008)

Credit: W. Myers

If we move the Earth closer…

Pierrehumbert (2002) Kleidon (2008)

A Brief History of Venus

Runaway Greenhouse

Ocean Evaporation

Photolysis Driven

Water Loss

Plate Tectonics Shutdown

Solar Luminosity Increases

Carbon & Sulfur Buildup

Our Future ? Studying Venus will have

implications on Earth’s evolution in the future

An extreme case: Tidally-locked Planets

Moses et al. (2013) Showman et al. (2013)

H2 v.s. CO2

Zonal Jet v.s. Divergent Flow Zhang and Showman (2014)

What we found

•  Molecular Mass Effect: Atmosphere with

lower molecular mass favors zonal jets and

equatorial superrotation.

•  Heat Capacity Effect: Atmosphere with

lower kappa favors day-to-night divergent

flow.

Prediction

•  We expect the super-earths/mini-Neptunes have

large meteorological diversity due to bulk

composition effects.

•  Atmosphere with jets tends to have smaller day-

night temperature difference due to larger

circulation efficiency.

•  Atmosphere with jets tends to have larger hot spot

phase shift.

Snellen et al. (2014)

Showman et al. (2013) Snellen et al. (2010)

(In)directly Detection the Wind

Internal Forcing

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•  Clouds/Hazes on radiation/chemistry

•  Convection/Waves

•  Magnetic effect ?

•  Surface/Boundary Layer Effect

Aerosols can have a huge Climate effect

•  Much of the chlorine and sulfur chemistry identified in Earth’s stratosphere was first proposed in early models of Venus’ photochemistry [Prinn, 1985].

•  Venus can be used for testing the limits of the photochemistry of sulfur species and their impact on climate (geoengineering).

Implication for Earth

Caldeira, Bala & Cao (2013)

An extreme case:

Atmosphere of Brown Dwarfs

Artigau et al. (2009); Radigan et al. (2012); Buenzli et al. (2012); Apai et al. (2013); Biller et al. (2013) etc.

Observations

Doppler Imaging of Luhman 16 B

Crossfield et al. (2014)

Jets

Isotropic Turbulences/Eddies

−0.50−0.45−0.40−0.35−0.30−0.25−0.20−0.15−0.10−0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

−60 −50 −40 −30 −20 −10 0 10 20 30

−80

−60

−40

−20

0

20

40

60

80

−1

Latitu

de

Zonal wind (m s )

−20 −15 −10 −5 0 5 10 15 20

−80

−60

−40

−20

0

20

40

60

80

Zonal wind (m s ) −1

Latitu

de

A

B

−3.0

−2.5

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

−0.50−0.45−0.40−0.35−0.30−0.25−0.20−0.15−0.10−0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

−60 −50 −40 −30 −20 −10 0 10 20 30

−80

−60

−40

−20

0

20

40

60

80

−1

Latitu

de

Zonal wind (m s )

−20 −15 −10 −5 0 5 10 15 20

−80

−60

−40

−20

0

20

40

60

80

Zonal wind (m s ) −1

Latitu

de

A

B

−3.0

−2.5

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Jets Formation in a 2D Shallow Atmosphere

Zhang and Showman (2014)

Simulated Light Curves

−0.50−0.45−0.40−0.35−0.30−0.25−0.20−0.15−0.10−0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

−60 −50 −40 −30 −20 −10 0 10 20 30

−80

−60

−40

−20

0

20

40

60

80

−1

Latitu

de

Zonal wind (m s )

−20 −15 −10 −5 0 5 10 15 20

−80

−60

−40

−20

0

20

40

60

80

Zonal wind (m s ) −1

Latitu

de

A

B

−3.0

−2.5

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Zhang and Showman (2014)

Minimum Recipe ?

•  Mass

•  Radius

•  Rotation

•  Temperature

•  Boundary Conditions

•  External/Internal Forcing

Composition

Wind Pattern

Climate

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Atlas of the Universe

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