planetary atmospheres: from here to light-years...
TRANSCRIPT
Planetary Atmospheres: From Here to Light-Years Away
Xi Zhang University of Arizona/LPL
1
NAOC Jul. 9, 2014
Planetary Atmosphere (Matter Energy Motion)
Chemistry
Dynamics Radiation
8
• 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?
9
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
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
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)
19
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
21
Faces of Jovian Aerosols
Zhang et al. (2013)
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
Planetary Atmosphere (Matter Energy Motion)
Chemistry
Dynamics Radiation
31
• 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
A Simple Framework
35
Force-Dissipation System
• External Forcing
• Internal Forcing
• Dissipation (Radiation/turbulences/drag)
External Forcing
36
• Milankovitch Cycle
• Faint Young Sun
• Runaway Greenhouse
• Ice-Albedo Feedback
• Magnetic Effect
Earth Venus!
Example: What Happened on Venus?
37
• 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
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
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.
Internal Forcing
46
• Clouds/Hazes on radiation/chemistry
• Convection/Waves
• Magnetic effect ?
• Surface/Boundary Layer 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)
Artigau et al. (2009); Radigan et al. (2012); Buenzli et al. (2012); Apai et al. (2013); Biller et al. (2013) etc.
Observations
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