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1. …†‡yNˆ‰2Š‹ŒThe chemical composition of the early terrestrial atmosphere:
Formation of a reducing atmosphere from CI-like material
George L. Hashimoto, Yutaka Abe, and Seiji Sugita

2. Late-Veneer2Š

Journal of Geophysical Research, 112, E05010, doi:10.1029/2006JE002844, 2007.

3. ÄÅ2ŠNÆÇ{”CÈÉ./ 0)(12 345 !678)

4. ‘’2ŠÊËÌÍ, ÎÏˆ‰, •l, Ðl2ŠNÑÒ•ŒyNˆ‰2Š
YŽ•yN2Š=•‘’€

1.…†‡yNˆ‰2Š‹Œ

L“kl!"{”C•–—N˜™ (e.g., Abe et al., 2000)
Lš›œ•$žŸ( p¡¢H2)N£¤ (e.g., Porcelli & Pepin, 2000)

YJ¥h!"{”C!"¦žŸ, §¨
L0.1ˆ‰"©_•ªCpH2O, CO2N!"¦žŸ(Ahrens et al., 1989)

L0.75ˆ‰"©_•ªCp«e~¬@!"§¨Y-§Š2ŠN•Œ(Ahrens & O’keefe, 1972)

LMagma OceanN•Œ (Matsui & Abe, 1986)2ŠN~•‘’®¯=•–—@°P…†‡yNˆ‰±²³´Y<-§Š2ŠNµ¶{”C·¸N•Œ(Matsui & Abe, 1986)

Y<•–¹N•Œ(=±²N•–—Nº»)(Abe et al., 2000)

Y<CI-like•"N…†(“Late veneer”)
L¼½¾¿ÀN%—U’tNÁÂ (e.g., Chou et al., 1983)

Late veneer9:;<Late veneer=>?@ABCDE=FGH
I JKLJMNOPQRNSTU2(e.g., Righter et al., 2003)VWVXXXY<ZN[G\]-^_`ab!"cN
defghOi=jklmNnopqr(Strom et al., 2005)

Y jklmN45 %=C-type(st"uvNwxc)(cf., S-type: 30%, X-type: 20%, D-type: 5%)2Š‹Œ=uv!"@°P(Bus & Binzel, 2002)!LHByNz#!"c=st{|}@~•€F•"E‚abƒ„U2

Righter & Drake, 1997
Late veneer9:

Late veneer9:;<Late veneer=>?@ABCDE=FGH
I JKLJMNOPQRNSTU2(e.g., Righter et al., 2003)
ê%—U’t;<Late veneer=>?@ABCDE=FGH
I JKLJMNOPQRNSTU2(e.g., Righter et al., 2003)

VWVXXXVWVXXX

Y<ZN[G\]-^_`ab!"cN
defghOi=jklmNnopqr

Y<ZN[G\]-^_`ab!"cN
defghOi=jklmNnopqr(Strom et al., 2005)(Strom et al., 2005)

Y jklmN45 %=C-type(st"uvNwxc)

Y jklmN45 %=C-type(st"uvNwxc)(cf., S-type: 30%, X-type: 20%, D-type: 5%)(Bus & Binzel, 2002)(cf., S-type: 30%, X-type: 20%, D-type: 5%)(Bus & Binzel, 2002)!LHByNz#!"c=st{|}@~•€F•"E‚abƒ„U2!LHByNz#!"c=st{|}@~•€F•"E‚abƒ„U2

Late veneer9:

Late veneer9:ZLÐlÕN!"cpÖ×NjklN;<Late veneer=>?@ABCDE=FGH
defghOiØÙI (StromJKLJMNOPQRNSTU2(e.g., Righter et al., 2003)\]-^&Ú=>!"c"©
et al., 2005_ÓÔ);<Late veneer=>?@ABCDE=FGH
I JKLJMNOPQRNSTU2(e.g., Righter et al., 2003)

Population 1VWVXXX

Schmidt & Housen, 1987N
Scaling rule

Y<ZN[G\]-^_`ab!"cN
Population
Population22
defghOi=jklmNnopqr

VWVXXX
Y<ZN[G\]-^_`ab!"cN
defghOi=jklmNnopqr(Strom et al., 2005)

v: !"¥h
Dc: Simple-Complex´Û&ÚY jklmN45 %=C-type(st"uvNwxc)
Df: ŽÜ\]-^&Ú(cf., S-type: 30%, X-type: 20%, D-type: 5%)(Bus & Binzel, 2002)
g: ÝÞß¥h!: !"càh!t: á€àh
!LHByN!"c=st{|}@~•€F•"": !"'hIE‚abƒ„U2(Chyba, 1991Wâãä)Y jklmN45 %=C-type(st"uvNwxc)(cf., S-type: 30%, X-type: 20%, D-type: 5%)(Bus & Binzel, 2002)!LHByNz#!"c=st{|}@~•€F•"E‚abƒ„U2

Late veneer9:

Late veneer9:;<Late veneer=>?@ABCDE=FGH
I JKLJMNOPQRNSTU2(e.g., Righter et al., 2003);<Late veneer=>?@ABCDE=FGH
I JKLJMNOPQRNSTU2(e.g., Righter et al., 2003)

Population of MBA(Bus & Binzel, 2002 modified by S. Hasegawa)

VWVXXX

4000

3000
2500
2000
1500
1000

VWVXXX

0.7
C-type (~45%)

0.6
Y<ZN[G\]-^_`ab!"cN
0.5
defghOi=jklmNnopqr
S-type (~35%)

Fraction of spectral type

3500

Number(Strom et al., 2005)(Strom et al., 2005)(Strom et al., 2005)

Y jklmN45 %=C-type(st"uvNwxc)
0.3

Y jklmN45 %=C-type(st"uvNwxc)

0.4(cf., S-type: 30%, X-type: 20%, D-type: 5%)
X-type (~20%)
D-type (~5%)

0.2(Bus & Binzel, 2002)

0.1!LHByN!"c=st{|}@~•€F•"
0
I 2 2.4 2.8 3.2 3.6 4 0E‚abƒ„U2(JAXAåæç&è¡é˜)
Semi-mejor axis [AU]500

Y<ZN[G\]-^_`ab!"cNdefghOi=jklmNnopqr(cf., S-type: 30%, X-type: 20%, D-type: 5%)(Bus & Binzel, 2002)!LHByNz#!"c=st{|}@~•€F•"E‚abƒ„U2

Late veneer2Š‹ŒNSTU
Y~•€•"N…† ( H2O-CO22Š@ïŒ(p>?âo'@bH)•y2Š‹ŒîTNÝ#U
Y<-Gš›N./01\ŸLK234žŸ(CO2, CH4, NH3)@¢N5h67oCW

YÖ×NÐAžŸ=~•€(Holland, 1984)
LBC¼½¾¿=QFMD1EF-{GG~•‘’®¯(e.g., Delano, 2001)=>ÎÏˆ‰2Š=CO2-N2-H2O@zŒO(Rubey, 1955; Kasting, 1993)

Y<ï89:•"(HCNF¢)NïŒ3;
L2ŠNC/OØ{”a'°P (e.g., Chameides & Walker, 1981)‘’<2Š(C/O > 1): HCNF¢NïŒ3;2~•<2Š(C/O < 1): HCNF¢NïŒ3;j!"ïŒ2Š‹Œ=HIH)JK•y2Š‹ŒîTNÝ#U
Y<-Gš›N./01\ŸLK234žŸ(CO2, CH4, NH3)@¢N5h67oCW
Y<ï89:•"(HCNF¢)NïŒ3;
L2ŠNC/OØ{”a'°P (e.g., Chameides & Walker, 1981)‘’<2Š(C/O > 1): HCNF¢NïŒ3;2~•<2Š(C/O < 1): HCNF¢NïŒ3;j2. Late-veneer2ŠëìÞí€îTëHCNïŒ3;NC/OØ=ÅU
(Chameides & Walker, 1981_ÓÔ)!"ïŒ2Š‹ŒîT!"ïŒ2Š‹ŒîT

Y…†‡y=!"¥h2 => !"xc=ðñ/§¨!"§ŠòNL<€FQuenchKh: 1000 - 3000 K(e.g., Abe, 1993)=> !"§ŠòïŒ(ó¨UŒO=(McKay & Boruchi, 1997; Ishimaru et al., 2005)=>!"ïŒ2Š=JK(>1000 K)EN#$‹Œôõö{¦žŸ)•í#$p•íúûN+,(quench)
quenchN÷øù•íúûüýÌÍ þ ÿ!üýÌÍ (TþTQ)MKhLMÞEN•í#$‹Œ_NBoO
II!"ïŒ2Š‹Œ_îTƒ„K•íúûüýÌÍ > ÿ!üýÌÍ (T > TQ)"nNKhEN•í#$‹Œ_%ÊVF@âÿ!

!6FœN•í#$‹Œ_*P+{NBCN=QB'RS(úûTU1¾V-\, W & XúûNúû¥hTR@Y#)•íúûüýÌÍ < ÿ!üýÌÍ (T < TQ)"ÿ!{•íúû@&G'G()X•í‹Œ@*T=>ìÞí€Z[@\3: “Gibbs energy minimization method”(•í#$: œNGibbs energy@Žj)(e.g., Chameides & Walker, 1981)

Late veneerN…†•" ~,]de~Y<…†•"NBulk‹Œ=CIuv_nT (e.g., Chou et al., 1983)
Y<CIuvÀN-O6\©=2op_Ñg

Late veneerN…†•" ~,]de~äGb’t‹Œ=>

LWet case ~20 wt % H2O (Wiik, 1956)
LDry case ~ 6 wt % H2O (Boato, 1954; Kerridge, 1985)

Y %ŠU’tI(EFmFe, SqÑgLFe=~tp,ÇV'~•‘’®¯_r•
LS=Fep,ÇVstGH
LFepuv@r'GCMn, Co, Ni, Cu=FepV'wxH(Wasson & Kallemeyn, 1988Nf-^)ÑgVb•íh: Table 2 (6’t, 30h; Š-: 20, µ¶-: 10)äGbìÞíf-^=JANAF table(Chase, 1998) ;http://webbook.nist.gov/chemistry/form-ser.html
IF¢ij

Y<yz#’t=~tp,ÇV'µ¶tCpnT
LNa(+1), Mg (+2), Al (+3), Si (+4), P (+5), K (+1), Ca (+2),
Ti (+4), Cr (+3) (Railsback, 2003)

Late veneer2Š ~,],4~Late veneer2Š ~,],4~
LHN2CO=H2O(plotV'GFG)
Wet case: >75 %Dry case: >50 %Lz#ŒO=H2O, CO2
L >10 barE=NH3@ >1 ppm
67oCH

QuenchQuenchLate veneer2Š ~,],4~
TQ > 1500 K

QuenchLate veneer2Š ~,],4~TQ ~ 500-1000 Kµ¶•{.klU@‚Cp@

LH2, CO@~30%_^BCH
H2/COØ=-O6\©pW-_(Sekine et al., 2003; Kress & McKay, 2004)

LH2, COE=Fm
I
CH4@ïŒ(~ 1 - 10%)

L1400-1800 KENH2, CON`aIFeSïŒ{”CONbc

QuenchQuench~tS:

Late veneer2Š ~,],4~CIuv: —=~•€I@X2©Nst(~3.5 wt %)_6}

TQ < 500 K

3;N”Gúû{|@‚CW¢xW=S}

stN~•úû
Fe2O3 + C => 2FeO + CO

LCH4=Graphite{rz(‘’€•"@µ¶-{cÖ)

1 molNC_~•tC{=2 molNFe@Y#=>3.5 wt%NC_~•V@C{=32.6 wt%NFe@Y#

LNH3=N2{rzQuenchCIuvNFe6\© ~ 20 wt%(Wasson & Kallemeyn, 1988)=>\{•_~•V@C{=S€O!
CIuvWâï?C2Š=•"€{‘’€ŒO_6}H

ÄÅ2ŠNSTU

3. ÄÅ2ŠNIÆÇ{”CÈÉ

ÄÅ2Š:•$£¤žŸ & •–—p#$•Vb¦žŸ2Š
=>H2{|}H
LH2=JKNkl±PEúûVH2O_ïŒ
L¹•ŒÌ{C, N=Ê‚ƒâoCH
(Wood, 1993)=>H2-H2O2Š
ÄÅ2ŠN©NSTU:„…F2Š†‡#ˆ: Hydrodynamic escape (Tian et al., 2005)
Impact erosion (Melosh & Vickely, 1989)
Giant impact (Genda & Abe, 2005)
ÄÅ2Š©=STU2 => Two-component modelTwo-component model ~R & O~
Component R: •$£¤žŸ & •–—p#$•Vb¦žŸ2Š
Component O: Late veneer{”C¦žŸ2Š

Two-component2Š;ÆÇ2Š@õö{#${~tCpnT

f2: H2N•¿O;2Late veneerN‰Šf(ÄÅ2ŠFV(Žq~•€): f = 1)
Component R: H2-H2O2Š, H2/H2O = 1pnT
L—p«e~¬@‹Å: iron-wustite buffer (Holland, 1984)(2xFe + O2 = 2FexO; x = 0.947)

JKE=H2/H2O>1 ÖŒ{=”p‘’€E‚Cƒ„U2

TQ < 800 K(.kúû@Y#)
H2-H2O2Š@CH4{rzf-valueNîT
%ŠU’tN%—UN¥G_¦ä => f_îTƒ„(;%—U H << C, N => NxEarth/NxO ~ 1)
(X = C, N)
Table 3. ˆ‰±PNH, C, N©
(Ronov & Taroshevsky, 1976; Holland, 1978;Kargel & Lewis, 1993)

4. ‘’2ŠÊËÌÍ, ÎÏˆ‰,Ðl, •l2ŠNÑÒ

Table 4. fNîTf = 0.1 -0.4 !
=>Conponent RN‰Š
I=2@G‘’<2ŠÊËÌÍ
Y<H2@†‡tCp2Š=~•èoCH(Ö×N·-ÀH2Op•5hNH2_†‡èŽCY#‚p)

Y<š›EUV@H2†‡N•U¿•-/(Tian et al., 2005)
L†‡‘Ï=š›œ•$žŸ†‡’=>ˆ‰•Œ‡yY<ë“8”•9Nš›EUV flux=Ö×N~10– (Ribas et al., 2005)
LH2†‡NTime scale ~ 5”• (Tian et al., 2005)‘’€2Š=R”•{—ba'˜Êèo'Gbƒ„U2ÎÏˆ‰2Š
Y<>10%NH2, CO, CH4, NH3_6}
Lï89:•"NïŒ3;2
Y<CH4, NH3=êGK234Šc
L-Gš›N./01\ŸN0œ
Y<‘’O›(ü{CH4)NÆÇØœT{= KineticsN•&@Y#LTQNîT{=!"§ŠòNP-T pathNîT@Sƒž
L!"§ŠòŸEN.kúû./ -^( p¡¢Z&W));ÄÅ2ŠpNÆÇ(§ŠòN!"’N¡vN70@Sƒž;«e~¬NìO0{”C~tbc

ÎÏ•l, Ðl2Š

7pB

Y<ˆ‰•„H2, CO, CH4, NH3_6}
2Š@•Œèob=)Late veneer2Š‹Œ_•B'7&€{)JL•l2ŠÀ{0.15-0.52·¸"©NH¢@ïŒI=>†‡Time scale=4 -13”•
I (f = 1Np@; f<1N£Ç=†‡{1/f –ÌÍ@WWCH)=>3;N”G¤ì€†‡{|@Y#Wq

Y<ÎÏˆ‰, •l, Ðl2Š=>10%NH2, CO, CH4, NH3_6¡EGbƒ„U2
Y<CIuvWâïŒtC2Š=•"€{‘’€“~tS:”@ÎˆY<ˆ‰BN%ŠU’tN>60%=Component R™šLÐlNÃ-ˆ•_D}E@CWq

Y<•y‘’<2Š=1 -10”•˜Êèobƒ„U2