Planetary Atmospheres I art by Alan Gutierrez Planetary Atmospheres - PowerPoint PPT Presentation

Planetary Atmospheres I art by Alan Gutierrez

Planetary Atmospheres I heated/energized from above by Sun photochemistry heated/energized from below by the planet internal heat greenhouse effect volcanism clouds winds storms surface evolution

Overview all planets + 7 dwarfs + Pluto have them (8 for real; 8 are wimpy) Terrestrial thin skins (200 km thick, or < 5% R) Gas Giants enormous (~ 20% R at Jup, ~ 45% R at Sat) Ice Giants moderate (~ 30% R) note: T at base of atm = 6800K (J), 6100K (S), 2500K (U/N)

Scale Height using hydrostatic equilibrium and ideal gas law: dP/dz = – g(z) ρ (z) P = ρ R T / µ = ρ k T / µ m find the atmospheric pressure as a function of altitude: P(z) = P o e – ∫ dz/HP(z) with the pressure scale height given by H P (z) = kT(z) / g(z) µ m where µ = mean molecular weight (in amu) m = 1.67 x 10 -24 g (one amu) so, pressure drops by factor of e in one scale height turns out to be the same for all substantial atmospheres: 10s of km …because T, g, and µ are all similar (at least in Jovian atmospheres near P = 1 bar)

16 Atmospheres PLANETS OTHERS comp (> 1%) P (bar) H (km) comp (> 1%) P (bar) H (km) Mercury O Na He < 10 -12 13 to 95 Moon He Ar 10 -15 65 Venus CO 2 N 2 92 16 Io SO 2 10 -8 Earth N 2 O 2 H 2 O 1.0 8.5 Europa O 2 10 -12 Mars CO 2 N 2 0.006v 11 Ganymede O 2 < 10 -11 Jupiter H 2 He 10 +6 24 Callisto CO 2 O 2 ? 10 -11 Saturn H 2 He 10 +6 47 Titan N 2 CH 4 Ar 1.5 20 Uranus H 2 He CH 4 10 +5 25 Triton N 2 10 -5 Neptune Pluto H 2 He CH 4 10 +5 23 N 2 10 -5 33 H P (z) = kT(z) / g(z) µ m

Earth’s Carbon www.climatescience.gov/Library/stratplan2003/final/ccspstratplan2003-chap7.htm

Ozone Stabilization http://www.discoveringantarctica.org.uk/12_using_data.html

Sun

Top 10 Differences Between Planetary and Stellar Atmospheres 1. Upper atmosphere heated by Sun. 2. Lower atmosphere heated by planet. 3. Volcanoes may add localized heating and chemical species. 4. Chemical reactions are abundant because of generally low T. 5. Clouds cause radical changes in opacity. 6. Phase transitions alter temp environment. 7. Crust and/or ocean will interact with atmosphere. 8. Weathering may change albedo/heating environment. 9. Storms may alter pressure/temp structure in atmosphere. 10. Life may affect composition and energy balance.

Generic Characteristics TROPOSPHERE convection sets temp temp drops with altitude infrared/radio clouds tend to form here STRATOSPHERE radiation (vs convection) temp increases with altitude optical/infrared MESOSPHERE radiation sets temp isothermal (or slight temp drop) portion of atmosphere mesopause forms second temp minimum on Earth + Titan THERMOSPHERE (IONOSPHERE) heating due to solar radiation ultraviolet 100 − 1000 Å photons blast e - , charged particles (aurorae) EXOSPHERE particles escape

Venus THERMO: 300 K vs 100 K day/night because CO 2 very efficient radiator MESO: isothermal [ STRATO: there really isn’t one! ] TROPO: greenhouse due to CO 2 heats diurnal/latitudinal/temporal temp variations less than 5K

Earth THERMO (IONO): temp increase due to UV abs. ionization of O 2 MESO: temp drop due to less O 3 production, CO 2 cooling STRATO: temp increase due to O 3 production (abs. UV+IR) TROPO: weather clouds at tropopause

Earth greenhouse gases H 2 O CO 2 CH 4 CFCs O 3 N 2 O

Greenhouse Effect

Venus vs. Earth : height

Venus vs. Earth : pressure

Mars

Mars THERMO: low, uniform temp due to CO 2 as efficient radiator and rapid rotation X MESO: thick isothermal layer [ STRATO: there really isn’t one! ] TROPO: T swings from 200K-300K eccentricity changes temp by 30K dust typically heats by 10K CO 2 cold-trapping changes P

Mars vs. Earth : height X

Mars vs. Earth : pressure X

Titan

Titan THERMO: cooled by HCN radiation MESO: hydrocarbon cooling, so T drops STRATO: up to 177K TROPO: clouds … and rain? similar overall atm structure to Earth although deeper

Titan vs. Earth : height

Titan vs. Earth : pressure

Terrestrial Atmospheres note temperature structures --- Earth’s O 3 causes stratosphere pressure scale height: H P (z) = kT(z) / g(z) µ m µ = mean molecular weight (in amu) m = 1.67 x 10 -24 g (one amu) Venus Earth Mars Titan H surf 16 km 8.5 11 20 P 100 km 10 -4 bar 10 -6 10 -8 10 -2

Terrestrial Atm Highlights Earth O 2 out of equilibrium + O 3 blanket largest % atmospheric H 2 O in Solar System 6 greenhouse gases Venus ~100 X Earth pressure SO 2 from vulcanism Mars sublimation/condensation cycles dust ~1% Earth pressure … wimpy O 3 blanket, H 2 O content Titan Earthlike structure and pressure hydrocarbons + nitriles

Solar System Explorers 07 Give any feature seen in the spectrum of a Solar System object (not the Sun) that makes that object’s emitted spectrum NOT a blackbody. Give the atomic/molecular species and wavelength affected, e.g. CO 2 as an absorber on Earth at 15 microns. 1. H2O on Earth, various 1-10 microns 2. CO2 on Earth, 15 microns 3. CH4 on Jupiter, 0.84 microns 4. O3 on Earth, 10 microns 5. CH4 on Jup/Sat/Ura/Nep, 0.8-1.0 microns 6. Michele 7. HCN on Titan, 14 microns 8. NH3 on Uranus, 0.5 microns 9. GeH4 on Jup, 5.2 microns 10. CH4 on Titan/Venus/Mars/Earth, 7.6 microns 11. LAND: Fe2O3 on Mars, 0.43 microns 12. C2H2, C2H4, C2H6 on Titan, various 13. CH3D on Jup, 5.5 microns 14. H2 on Jup/Sat/Ura/Nep, 25 microns 15. O2 on Earth, 10 microns 16. CH4 on Pluto/Charon, 1.7-1.8 microns 17. H2SO4 on Venus, ??? microns 18. 19. 20.

Solar System Explorers 2012 Give any feature seen in the spectrum of a Solar System object (not the Sun) that makes that object’s emitted spectrum NOT a blackbody. Give the atomic/molecular species and wavelength affected, e.g. CO 2 as an absorber on Earth at 15 microns. 1. SO2 at Venus at 8.7 microns 2. SO2 at Io at 1.36 mm (emission) 3. H2O at Jupiter at 6191 A 4. CH4 at Jupiter ~8000 A 5. CO at Earth at ??? 6. C2H2 at Jupiter at 14 microns 7. HgS at Venus at 0.6 microns 8. N2 at Triton at 2.15 microns (reflectance) 9. He at Jupiter via Shoemaker-Levy 584 A (emission) 10. H2O at Enceladus 3 microns 11. CO2 at Mars (poles) 15 microns 12. SO at Io 1.7 microns (forbidden) 13. C3H8 at Titan 13 microns 14. high-Ca pyoxene at Mercury at 1 micron 15. O2 at Earth at 7500 A 16. CO at Venus (night) 2.3 microns 17. CH4 at Jupiter at every wavelength you can imagine … just about 18. CH3D (mono-deuterated) at Titan 1.6 microns 19. O3 at Mars 2500A 20. PH3 at Saturn 9-12 microns

Solar System Explorers 08 Describe one feature of a non-solar atmosphere in the Solar System that makes it different from EVERY other non-solar atmosphere. (no spectral features) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

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