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
art by Alan Gutierrez
heated/energized from above by Sun photochemistry heated/energized from below by the planet internal heat greenhouse effect volcanism clouds winds storms surface evolution
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)
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) = Po e – ∫ dz/HP(z) with the pressure scale height given by HP(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)
Mercury
O Na He < 10 -12 13 to 95
Moon
He Ar 10 -15 65
Venus
CO2 N2 92 16
Io
SO2 10 -8
Earth
N2 O2 H2O 1.0 8.5
Europa
O2 10 -12
Mars
CO2 N2 0.006v 11
Ganymede
O2 < 10 -11
Jupiter
H2 He 10 +6 24
Callisto
CO2 O2? 10 -11
Saturn
H2 He 10 +6 47
Titan
N2 CH4 Ar 1.5 20
Uranus
H2 He CH4 10 +5 25
Triton
N2 10 -5
Neptune
H2 He CH4 10 +5 23
Pluto
N2 10 -5 33
PLANETS OTHERS comp (> 1%) P (bar) H (km) comp (> 1%) P (bar) H (km) HP(z) = kT(z) / g(z) µ m
www.climatescience.gov/Library/stratplan2003/final/ccspstratplan2003-chap7.htm
http://www.discoveringantarctica.org.uk/12_using_data.html
TROPOSPHERE convection sets temp temp drops with altitude infrared/radio clouds tend to form here STRATOSPHERE radiation (vs convection) temp increases with altitude
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
THERMO: 300 K vs 100 K day/night because CO2 very efficient radiator MESO: isothermal [ STRATO: there really isn’t one! ] TROPO: greenhouse due to CO2 heats diurnal/latitudinal/temporal temp variations less than 5K
THERMO (IONO): temp increase due to UV abs. ionization of O2 MESO: temp drop due to less O3 production, CO2 cooling STRATO: temp increase due to O3 production (abs. UV+IR) TROPO: weather clouds at tropopause
greenhouse gases H2O CO2 CH4 CFCs O3 N2O
THERMO: low, uniform temp due to CO2 as efficient radiator and rapid rotation 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 CO2 cold-trapping changes P
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
note temperature structures --- Earth’s O3 causes stratosphere pressure scale height: HP(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
Hsurf 16 km 8.5 11 20 P100 km 10-4 bar 10-6 10-8 10-2
Earth
O2 out of equilibrium + O3 blanket largest % atmospheric H2O in Solar System 6 greenhouse gases
Venus
~100 X Earth pressure SO2 from vulcanism
Mars
sublimation/condensation cycles dust ~1% Earth pressure … wimpy O3 blanket, H2O content
Titan
Earthlike structure and pressure hydrocarbons + nitriles
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. CO2 as an absorber on Earth at 15 microns.
18. 19. 20.
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. CO2 as an absorber on Earth at 15 microns.
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.