climates of terrestrial planets
DESCRIPTION
Climates of Terrestrial Planets. Dave Brain LASP / CU Boulder. An interesting question with no definite answer will be posed here, for you to look at until the lecture actually starts. Do magnetic fields affect planet surfaces?. Do magnetic fields affect atmospheres?. - PowerPoint PPT PresentationTRANSCRIPT
Climates of Terrestrial Planets
Dave Brain
LASP / CU Boulder
Do magnetic fields affect planet surfaces?
Do magnetic fields affect atmospheres?
Do magnetic fields affect climate?
An interesting question with no definite answer will be posed here, for you to look at until the lecture actually starts
Approach
Climates Heliophysics
I. Climates
II. Changing Climates
III. Atmospheric Escape Processes
[ Break ]
Heliophysics Climates
IV. External Drivers
V. Internal Drivers
VI. Prospects
I. Climates
Contemporary ClimatesVenus Earth Mars
Surface Temperature
740 K 288 K 210 K
Surface Pressure 92 bars 1 bar 7 mbar
Composition 96% CO2; 3.5% N2 78% N2; 21% O2 95% CO2; 2.7% N2
H2O content 20 ppm 10,000 ppm 210 ppm
Precipitation None at surface rain, frost, snow frost
Circulation1 cell / hemisphere,
quiet at surface but very active aloft
3 cells / hemisphere, local and regional
storms
1-2 cells / hemisphere or patchy circulation, global dust storms
Maximum surface winds
~3 m/s > 100 m/s ~30 m/s
Seasonal Variation
None Comparable northern and southern seasons
Southern summer more extreme
II. Changing Climates
A very exciting question will be asked here•
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Four Ways to Change TSurface
Solar Output Planetary Albedo
Greenhouse Gas Content Planetary Orbital Elements
NASA Ames / J. LaskarRibas et al., 2010
Evidence for Climate ChangeVenus
Matsui et al., 2012
Strom et al., 1994
Evidence for Climate ChangeMars
Geomorphology
Isotopes
Geochemistry
Jakosky and Phillips, 2002
Evidence for Climate ChangeEarth
IceBubbles compositionIsotopes temperaturesPollen conditions
Trees and CoralSeparation growth rate climate
SedimentFossils / pollen conditionsComposition temperatureLayering climate shiftsTexture environment
Atmospheric Source and Loss Processes
Source
Outgassing
Loss
Escape to spaceHydrodynamic escape
Source and Loss
ImpactsSurface exchange
III. Atmospheric Escape Processes
Wow – another question!•
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Requirements for Escape
Escape Energy
Directed Upward
No Collisions
Escape from exobase region
Venus Earth Mars
vesc 10 km/s 11 km/s 5 km/s
E(H+) 0.5 eV 0.6 eV 0.1 eV
E(O) 9 eV 10 eV 2 eV
Reservoirs for Escape
Thermosphere
T(z)
Diffusive equilibrium
V: ~120-250 kmCO2, CO, O, N2
E: ~85-500 kmO2, He, N2
M: ~80-200 kmCO2, N2, CO
Exosphere
“collisionless”
Ballistic trajectories
V: ~250-8,000 kmH
E: ~500-10,000 kmH, (He, CO2, O)
M: ~200-30,000 kmH, (O)
Ionosphere
Small % of neutrals
Incident energy forms peaks
V: ~120-300 kmO2
+, O+, H+
E: ~75-1000 kmNO+, O+, H+
M: ~80-200 kmO2
+, O+, H+
Lots of red here
(I got tired)
Sur
face
Spa
ce
Terrestrial Planet Magnetospheres
Intrinsic Magnetosphere Induced Magnetosphere
Cartoons courtesy S. Bartlett
Escape Processes
Neutral Particle Processes
Jeans Escape (E,M)
Photochemical Escape (V,M)
O2+ + e- O* + O*
Sputtering (V, M)
Charged Particle ProcessesIon pickup (V,M)
Ion outflow (V,E,M)
Bulk plasma escape (V,M)
Moore et al., 1999
Luhmann and Kozyra, 1991
Alternative Classification Scheme
• Electric fields accelerate charged particles
• Can loosely identify pickup, Hall, and pressure gradient escape
• Highlights that combinations of mechanisms can accelerate ions
Pickup Hall Electron Pressure Gradient