chemistry of planetary atmospheres– observations, experiments, computations and modeling
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Chemistry of Planetary Atmospheres– Observations, Experiments, Computations and Modeling. Yuk Ling Yung ( 翁玉林) Caltech. Seminar at NSRRC 19 July 2012. - PowerPoint PPT PresentationTRANSCRIPT
Chemistry of Planetary Atmospheres– Observations, Experiments, Computations and Modeling
Yuk Ling Yung (翁玉林)Caltech
Seminar at NSRRC19 July 2012
Cheng, B. M., E. P. Chew, C. P. Liu, M. Bahou, Y. P. Lee, Y. L. Yung, and M. F. Gerstell. (1999). "Photo-induced Fractionation of Water Isotopomers in the Martian Atmosphere." Geophysical Research Letters 26(24): 3657-3660. Lee, A. Y. T., Y. L. Yung, B. M. Cheng, M. Bahou, C. Y. Chung, and Y. P. Lee. (2001). "Enhancement of Deuterated Ethane on Jupiter." Astrophysical Journal 551(1): L93-L96. Bahou, M., C. Y. Chung, Y. P. Lee, B. M. Cheng, Y. L. Yung, and L. C. Lee. (2001). "Absorption Cross Sections of HCl and DCl at 135-232 Nanometers: Implications for Photodissociation on Venus." Astrophysical Journal 559(2): L179-L182. Cheng, B. M., H. C. Liu, H. K. Chen, M. Bahou, Y. P. Lee, A. M. Mebel, L. C. Lee, M. C. Liang, and Y. L. Yung. (2006). “Absorption cross sections of NH3, NH2D and ND3 in the spectral range 140-220 nm and its implication for planetary isotopic fractionation.” Astrophys. J. 647 1535-1542. Liang, M. C., B. M. Cheng, H. C. Lu, H. K. Chen, M. S. Alam, Y. P. Lee and Y. L. Yung. (2007). “Isotopic fractionation of nitrogen in ammonia in the troposphere of Jupiter.” Astrophys. J. Lett. 657 L117-120, doi:0004-637X.
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Dr. Liang Mao-Chang
Academia Sinica
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Cheng, B. M., E. P. Chew, C. P. Liu, M. Bahou, Y. P. Lee, Y. L. Yung, and M. F. Gerstell. (1999). "Photo-induced Fractionation of Water Isotopomers in the Martian Atmosphere." Geophysical Research Letters 26(24): 3657-3660. Lee, A. Y. T., Y. L. Yung, B. M. Cheng, M. Bahou, C. Y. Chung, and Y. P. Lee. (2001). "Enhancement of Deuterated Ethane on Jupiter." Astrophysical Journal 551(1): L93-L96. Bahou, M., C. Y. Chung, Y. P. Lee, B. M. Cheng, Y. L. Yung, and L. C. Lee. (2001). "Absorption Cross Sections of HCl and DCl at 135-232 Nanometers: Implications for Photodissociation on Venus." Astrophysical Journal 559(2): L179-L182. Cheng, B. M., H. C. Liu, H. K. Chen, M. Bahou, Y. P. Lee, A. M. Mebel, L. C. Lee, M. C. Liang, and Y. L. Yung. (2006). “Absorption cross sections of NH3, NH2D and ND3 in the spectral range 140-220 nm and its implication for planetary isotopic fractionation.” Astrophys. J. 647 1535-1542. Liang, M. C., B. M. Cheng, H. C. Lu, H. K. Chen, M. S. Alam, Y. P. Lee and Y. L. Yung. (2007). “Isotopic fractionation of nitrogen in ammonia in the troposphere of Jupiter.” Astrophys. J. Lett. 657 L117-120, doi:0004-637X.
What Drives Evolution? () Mars (Isotopes) Venus (Loss of Ocean) Titan and Enceladus Exoplanets (Life?) Conclusions
Today’s Outline
What Drives Evolution? () Mars (Isotopes) Venus (Loss of Ocean) Titan and Enceladus Exoplanets (Life?) Conclusions
Today’s Outline
Mars: Gone with the (Solar) Wind
Isotopic Fractionation
Kass and Yung Science 1995
What Drives Evolution? () Mars (Isotopes) Venus (Loss of Ocean) Titan and Enceladus Exoplanets (Life?) Conclusions
Today’s Outline
Venus (Loss of Ocean)
Yung and DeMore Icarus 1982
Yung et al. JGR 2008
What Drives Evolution? () Mars (Isotopes) Venus (Loss of Ocean) Titan and Enceladus Exoplanets (Life?) Conclusions
Today’s Outline
Titan/Enceladus
Yung, Allen, Pinto ApJ 1984
Liang et al. ApJL 2007
Parkinson et al. 2008
Enter Cassini
• Launched in 1997• Arrived in Saturn
system in 2004• Wide array of
instruments– Ultraviolet Imaging
Spectrograph (UVIS)
Lorenz + Mitton 02
[Moses et al., JGR, 2005]
Titan
• Atmosphere: Mostly nitrogen (98%), with methane and various hydrocarbons
• Surface pressure of ~1.5 atm
• Temperature of atmosphere ranges from 80K to 180K
Hidden in Haze
• Thick layers of haze obscure the surface
• Photochemistry drives complex suite of organic reactions
• These organics have distinct absorption features in the UV region of spectrum
Hidden in Haze
• Motivation:– What chemistry occurs
on Titan, and where?– How might the products
of this chemistry vary in space and time?
– Connection to lower atmosphere/surface?
Stargazing with Cassini UVIS
• Cassini UVIS instrument– EUV Spectrograph used for
solar and stellar occultations– FUV Spectrograph used for
stellar occultations– Measures integrated UV
photon flux
(from Esposito et al. 2003)
Stargazing with Cassini UVIS• Cassini UVIS instrument
– EUV Spectrograph used for solar and stellar occultations
– FUV Spectrograph used for stellar occultations
– Measures integrated UV photon flux
• Occultations with UVIS can probe atmospheric regions that no other instruments can easily observe
Photon Counts to Optical Depth
• Process in two steps:– Calculate Io (λ) spectrum from above atmosphere– Optical depth is calculated as:
τ (λ,h) = - ln [I (λ,h) / Io (λ)]where I (λ,h) is the integrated photon flux at each wavelength λ and occultation ray height h
Optical Depth to Abundance
• Species absorption cross-sections– From laboratory measurements
• Instrument response function– For given species abundance (cm-2), can calculate
contribution to optical depth as seen by UVIS• Rodgers retrieval methodology
– Finds best fit parameters of forward model in iterative process that minimizes cost function
• J(x) = (x-xa)T Sa-1 (x-xa) + (y-Kx)T Se
-1 (y-Kx)
Abundance to Density
• Assume spherically symmetric atmosphere
• Convert line of sight abundance to local density using inverse Abel transform
Tholins and Haze
Invited Talk (AGU 2007) Yung et al., Oxidants on Small Icy Bodies and Snowball Earth
H2O: need 20000 resolution 900 -1300 A5000 resolution 550 -900 A
N2: Glenn Stark has been doing a lot of work on this; 800 - 1000ANeed resolution of at least 100000.
What Drives Evolution? () Mars (Isotopes) Venus (Loss of Ocean) Titan and Enceladus Exoplanets (Life?) Conclusions
Today’s Outline
Are We Alone in the Universe?
There is life out there in the universe which is smarter than we are, or we're the most intelligent life in the universe. Either way, it's a mighty sobering thought.
Library of Helaxandria, 2007
Extrasolar Planets (HD 189733b )
Tinetti et al. Nature 2007
Molecules in Exoplanets
H2O, CO, CO2, CH4
Tinetti et al., Nature, 448, 163, 2007
Water, T-P at the terminator
Water line list: BT2Barber et al., 2006
HD 209458b
Hydrocarbons
CO + h C + OC + H2 + M 3CH2 + M2 3CH2 C2H2 + 2HC2H2 + H + M C2H3 + MC2H3 + H2 C2H4 + HC2H4 + H + M C2H5 + MC2H5 + H 2CH3
CH3 + H + M CH4 + M
CH4 Production
bottleneck
Li et al. PNAS 2008
What Drives Evolution? () Mars (Isotopes) Venus (Loss of Ocean) Titan and Enceladus Exoplanets (Life?) Conclusions
Today’s Outline
Planets have evolved
Isotopic composition provides clues
Exoplanets provide testbeds for evolution
Biological evolution is possible in exoplanets
Conclusions: Unifying Theme
夢中遇外星人 夜深闌靜後 獨步上小丘驀見山盡處 鋩鋩七火球划破長空過 飛向一母舟稍待齊集合 即去不復留余生也有幸 遇此外星儔伊人竟是誰 莫非織與牛羽化宇宙間 遨與造物遊彼族之文明 豈我所能究乍見一伊鐵 大頭又大眸
深邃不可測 似懷千歲憂我乃漢族人 唯知仁德修敦睦安天命 亙古寡敵仇惜哉輕科學 昧於新潮流百年遭萬劫 國難無止休頻頻被魚肉 不如奴與囚爾族識天機 必有濟世謀拯民於水火 復我唐漢周欲答已驚醒 但見光柔柔頃刻電光逝 仰望空悵惆遙思遠一方 朝暉撫神州
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Backup Slides
x: Machida et al. [1995] +: Bernard et al. [2006]