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 Climates VenusEarthMars Surface Temperature 740 K288 K210 K Surface Pressure 92 bars1 bar7 mbar Composition 96% CO 2 ; 3.5% N 2 78% N 2 ; 21% O 2 95% CO 2 ; 2.7% N 2 H 2 O content 20 ppm10,000 ppm210 ppm Precipitation None at surfacerain, frost, snowfrost Circulation 1 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

Four Ways to Change T Surface Solar OutputPlanetary Albedo Greenhouse Gas ContentPlanetary Orbital Elements NASA Ames / J. Laskar Ribas et al., 2010

Evidence for Climate Change Venus Matsui et al., 2012 Strom et al., 1994

Evidence for Climate Change Mars Geomorphology Isotopes Geochemistry Jakosky and Phillips, 2002

Evidence for Climate Change Earth Ice Bubbles  composition Isotopes  temperatures Pollen  conditions Trees and Coral Separation  growth rate  climate Sediment Fossils / pollen  conditions Composition  temperature Layering  climate shifts Texture  environment

Atmospheric Source and Loss Processes Source Outgassing Loss Escape to space Hydrodynamic escape Source and Loss Impacts Surface exchange

III.Atmospheric Escape Processes

Wow – another question!

Requirements for Escape Escape Energy Directed Upward No Collisions Escape from exobase region VenusEarthMars v esc 10 km/s11 km/s5 km/s E(H + )0.5 eV0.6 eV0.1 eV E(O)9 eV10 eV2 eV

Reservoirs for Escape Thermosphere T(z)  Diffusive equilibrium V: ~ km CO 2, CO, O, N 2 E: ~ km O 2, He, N 2 M: ~ km CO 2, N 2, CO Exosphere “collisionless” Ballistic trajectories V: ~250-8,000 km H E: ~500-10,000 km H, (He, CO 2, O) M: ~200-30,000 km H, (O) Ionosphere Small % of neutrals Incident energy forms peaks V: ~ km O 2 +, O +, H + E: ~ km NO +, O +, H + M: ~ km O 2 +, O +, H + Lots of red here (I got tired) Lots of red here (I got tired) Surface Space

Terrestrial Planet Magnetospheres Intrinsic MagnetosphereInduced Magnetosphere Cartoons courtesy S. Bartlett

Escape Processes

Neutral Particle Processes Jeans Escape (E,M) Photochemical Escape (V,M) O e -  O* + O* Sputtering (V, M)

Charged Particle Processes Ion 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 PickupHallElectron Pressure Gradient