タイタン大気進化過程のおさらいと h 2 原始大気の可能性
DESCRIPTION
タイタン大気進化過程のおさらいと H 2 原始大気の可能性. 惑星物理研究室 中神 雄一 [email protected]. タイタンの概要 （現在）. 土星最大の衛星 直径 ： ～ 5200 km 濃い大気 N 2 : 1.5 bar CH 4 : ~ 0.06 bar H 2 etc … 地表面温度 ~94K. http://nssdc.gsfc.nasa.gov/image/planetary/saturn/titan.jpg. 同位体比・組成. H,N 同位体比 : 大規模な大気散逸を示唆 - PowerPoint PPT PresentationTRANSCRIPT
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5200 km N2 : 1.5 bar CH4 : ~ 0.06 bar H2 etc ~94K
http://nssdc.gsfc.nasa.gov/image/planetary/saturn/titan.jpg
- H,N : - 15N/14N : 1.3-1.6x (Waite et al.,2005) 1.6 100 (Lunine et al.,1999) - CH3D/CH4 2-5 x (Orton,1992) 100 (Lunine et al.,1999) CH4,N2 : [CH4]
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H2 - - (Tian et al.,2005)H2 - - H2
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H2
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p : r : : : 0 : r p G :k : T : M : r m :
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Pure H2 , EUV
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p : : m: kB : u : : g : : T : q :
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u : a : (Lamers and Cassinelli, 1999)
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H2 (Tian et al., 2005)x 2.5x 5.0 - H2 EUV 700-800 K EUV x1, x2.5, x.5.0 (Tian et al.,2005)
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H2 EUV H210-3 30%H2H2Tian et al.,2005
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H2 - 3 - H2
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H2
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- N2 NH3N2 - CH4
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Subnebula C~OOH2O OH2O (Lunine and Tittemore, 1993)
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[N2]/[CH4] = 10-3 ~ 10-4N2 > CH4 (Lunine et al.,1985)CH4 richCH4 N2 H2O, CO, CH4 C/O
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N2N2 36,38Ar/N2 - Ar (Waite et al.,2005)
NH3 - - N2 - [NH3]/[H2O] ~ 10-2 100 bar N2 (Owen, 2000)
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- high opacity - (Lunine and Stevenson. 1987)
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(172K) CH4 0.18 bar
(Lunine et al.,1985)
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NH3N2 NH3, N2H4 - Ts > 150 K 1 N2 (Lunine et al.,1989)(Atreya et al.,1978) Ts > 150 Kunknown
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CH
-CH440Myr (Yung et al.,1984) - CH4 45 ~ 6bar - D/H (CH3D/CH4) - CH3D/CH4 2-5 x (Orton,1992) 100 (Lunine et al.,1999)CH1450 CHH2H
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CH4 - - CH4
12C/13C 1 xEarth
http://saturn.jpl.nasa.gov/multimedia/images/CH4 Lake?234x73 km
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subnebula NH3N2
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H2 - 10 104 [Pa] (Mosqueira et al.2003)
H2 102-103 [bar]
[H2]:[N2]:[CH4]=2:1:1NH3, CH4 unknown
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Nebula Nebula (N2/CH4, )- blow off (H2) - Nebula
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EUV Tian et al.,2005 - NH3, CH4 - - NH3 N2
Nebula
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- nebula - EUV Nebula H2 - CH4, NH3
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Blowoff Fi(t)j : H2, N2, CH4FH2 : H2mH2 : g : re : k : T : (T=100K) bi : bN2 = 1.8751019T0.82bCH4 = 2.30 1019T0.765(Mason and Marreo, 1970)(Hunten et al.,1987)
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N2blowoff H2 H2 HN2 : N2 Hunten et al.,1973If
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EUV
Pepin, 1991G : Mt : [erg cm-2 s-1]
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re = 5,000 km t0 = 5 Myr ()H2 : 100 bar, N2 : 100 bar (const), CH4 : 40 bar
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H2 H2 < 100 bar CH4 H2 10 bar H2
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CH4 H2, H2 H2100~20 bar, CH4 10~20 bar CH4 ~ 6 bar
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N2 H240 ~ 60 bar N2 ~ 45 bar
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EUV H2 N2, CH4 blowoff H2 ; 10 ~ 1000 bar
N2CH4100 bar()bar??????~ 45 bar~ 6 bar
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H2 40~60 bar
- subnebula H2 - CH4 ~1/10
N2CH4()100 bar()10~15 bar~ 45 bar~ 6 bar
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CH4-C2H6 CH4 C2H6 0.6 km C2H6 (Lunine and Stevenson, 1985)