Photochemistry in the Atmospheres of

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Photochemistry in the Atmospheres of Hot
Jupiters Yuk L. Yung1, Mao-Chang Liang2, Michael
Line1 and Giovanna Tinetti3 1Division of
Geological and Planetary Sciences, California
Institute of Technology, USA 2Research Center for
Environmental Changes, Academia Sinica,
Taiwan 3University College London, UK. Molecules
in the Atmospheres of Extrasolar planets Paris,
Nov 19-21, 2008
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Todays Outline

• Start with colder planets
• HD209458b
• H2O, CO, CO2, CH4 and hydrocarbons
• Sulfur species, Nitrogen species
• Lessons from solar system

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HD209458b
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Chemical processes

• Chemical composition different from that of
  Jupiter
• CO and H2O are abundant CH4 not abundant
• UV radiation a lot more enhanced
• Can break up more molecules
• Boost subsequent chemical reactions
• Performing photochemical calculation for HD
  209458b

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Properties of HD 209458b

• Best known planet
• First discovered transiting planet (Henry et al.
  2000)
• First atmosphere detection (Charbonneau et al.
  2001)
• First exosphere detection (Vidal-Madjar et al.
  2003)
• Orbiting HD 209458 G0V-type star
• 0.05 AU or 3.5 days
• Inclination angle 85?
• Radius 1.54 RJ and mass 0.68 MJ

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One-dimensional photochemical model

• Solving mass continuity equation
• Kzz K0?n-?, ? ? 0.5
• Temperature profile from thermochemical
  calculation
• Chemical reactions from, for example, Yung and
  DeMore (1999)

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Temperature profiles
Barman et al. 2002
Fortney et al. 2003
F/2?
Jupiter
F/2?
F/4?
Seager et al. 2000
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Model atmosphere
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Atomic Hydrogen
H Production high H/H2 ratio
H2O Production
CO h? ? C O O H2 ? OH H OH H2 ? H2O H
H2O h? ? H OH OH H2 ? H2O H
Net H2 h? ? 2H
Net CO 2H2 h? ? C H2O 2H
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Hydrocarbons
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• 2?CO h? ? C O
• 2?C H2 M ? 3CH2 M
• 3CH2 3CH2? C2H2 2H
• C2H2 H M ? C2H3 M
• C2H3 H2 ? C2H4 H
• C2H4 H M ? C2H5 M
• C2H5 H ? 2CH3
• 2? CH3 H M ? CH4 M
• 2? O H2 ? OH H
• 2? OH H2 ? H2O H
• 2? H H M ? H2 M
• net 2CO 3H2 ? CH4 2H2O

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N2
HCN
NH3
NH2
N
CH3NH2
CN
NO
NH
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S2
SH
S
H2S
SO
HSO
S3
SO3
S5
S4
S6
SO2
S8
H2SO4
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Friedson et al., Icarus, 2002
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Conclusions

• Common photochemistry hundreds of molecules,
  thousands of reactions
• Similar Processes Catalytic cycles, evolution,
  hydrodynamic escape, thermal inversion
• Advice to modelers
• Dans ce meilleur des mondes possibles tout est
  au mieux.
• (In this best of possible worlds all is for
  the best.)
• Advice to observers
• Dieu nest par pour les gros bataillons, mais
  pour ceux qui tirent le mieux.
• (God is on the side not of the heavy
  battalions, but of the best shots.)

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Acknowledgements

• NASA and ESA
• Yungs Group at Caltech
• Liang Ph.D. Thesis 2005
• Meadows et al. 2008
• Yung and DeMore (1999) Book

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Back-up slides
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OCS
OCS
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Conclusions

• Common photochemistry hundreds of molecules,
  thousands of reactions
• Similar Processes Catalytic cycles, evolution,
  hydrodynamic escape, thermal inversion
• Advice to modelers
• Dans ce meilleur des mondes possibles tout est
  au mieux
• (In this best of possible worlds all is for
  the best.)
• Advice to observers
• Dieu nest par pour les gros bataillons, mais
  pour ceux qui tirent le mieux.
• (God is on the side not of the heavy
  battalions, but of the best shots.)