Isotopic analysis of soluble organic matter in meteorites

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Published on March 10, 2014

Author: iaingilmour

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Presented at the workshop Isotopes in Astrochemistry: An Interstellar Heritage for Solar System Materials? Lorentz Center, Universiteit Leiden, December 5-9 2011.

The matter comprising the Sun and the planets, well as the comets and asteroids, originated in the dense core of an interstellar cloud over 4.6 billion years ago. The aim of the workshop will be to obtain a clearer picture of the fate of observed interstellar isotopic fractionation patterns as they were incorporated into the protosolar nebula. A major goal would be to ascertain which of the molecular isotopic signatures found in primitive Solar System matter are indicative of pristine interstellar molecules.

Isotopic analysis of soluble organic matter in meteorites Iain Gilmour Lorentz Center, University of Leiden, December 2011

• Definition and Astrochemical significance • Analysis • Classes of compounds • Isotopic studies • Relationship to IOM Soluble organic matter in meteorites

0 24 48 72 96 120 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 50 years of publications related to meteoritic organics FallofMurchison&Allende ALH84001 “Organizedelements”inOrgueil GCMS development irm-GCMS development SIMS development Publications

Inorganic Organic IOM SOM Organic matter in Murchison

Meteorite Solvent Extract Organic solvents/water based extraction GCxGC-TOF/MS ESI-FTICR/MS Preparative Chromatography Polar LCMS Derivitisation GCMS GCIRMS Apolar GCMS GCIRMS Aromatic GCMS GCIRMS ... Residue isolation Acid treatment/CsF Pyrolysis Isolation and analysis of SOM

compounds identified in this and other extracts are pre- sented in the Appendix. The compounds extracted were dominated by C10 and C15 compounds, as reported by Sephton et al. (2001b). In this study we unambiguously identify several of these compounds containing ten car- bons including camphor (II), borneol (III), terpineol (V) and pinenone (VI); whereas other (C10) compounds are tentatively identified. Of these compounds camphor has previously been identified in the Orgueil carbonaceous chondrite (Studier et al., 1968). A series of C15 compounds previously unidentified in Orgueil are also present and pounds include cadalene (XIII; Fig. 3); calamenene (IX; Fig. 3), 5,6,7,8-tetrahydrocadalene (XI; Fig. 3) and a curcumene (XII; Fig. 3), a series of n-alkanes (C13–C20) and pristane and phytane. The more volatile com- pounds such as tolylethanone (IV), camphor (II), bor- neol (III), terpineol (V) and pinenone (VI) are evident at lower relative abundance possibly due to losses during reduction of the solvent volume prior to GC injection. A dominant peak observed in the chromatogram could not be positively identified (retention time $28 min; unknown B, see Fig. 4), but could possibly be a com- Fig. 1. Total current ion chromatogram of the supercritical fluid extract (SFE) of a fragment of the Orgueil meteorite. Structures for I to XIII are given in the Appendix; ^=n-alkane (n-C13À20), A=unknown A. Appendix 46 J.S. Watson et al. / Organic Geochemistry 34 (2003) 37–47 Appendix 46 J.S. Watson et al. / Organic Geochemistry 34 (2003) 37–47 Appendix 46 J.S. Watson et al. / Organic Geochemistry 34 (2003) 37–47 Appendix 46 J.S. Watson et al. / Organic Geochemistry 34 (2003) 37–47 Contaminants in Orgueil (Watson et al. 2003)

compounds identified in this and other extracts are pre- sented in the Appendix. The compounds extracted were dominated by C10 and C15 compounds, as reported by Sephton et al. (2001b). In this study we unambiguously identify several of these compounds containing ten car- bons including camphor (II), borneol (III), terpineol (V) and pinenone (VI); whereas other (C10) compounds are tentatively identified. Of these compounds camphor has previously been identified in the Orgueil carbonaceous chondrite (Studier et al., 1968). A series of C15 compounds previously unidentified in Orgueil are also present and pounds include cadalene (XIII; Fig. 3); calamenene (IX; Fig. 3), 5,6,7,8-tetrahydrocadalene (XI; Fig. 3) and a curcumene (XII; Fig. 3), a series of n-alkanes (C13–C20) and pristane and phytane. The more volatile com- pounds such as tolylethanone (IV), camphor (II), bor- neol (III), terpineol (V) and pinenone (VI) are evident at lower relative abundance possibly due to losses during reduction of the solvent volume prior to GC injection. A dominant peak observed in the chromatogram could not be positively identified (retention time $28 min; unknown B, see Fig. 4), but could possibly be a com- Fig. 1. Total current ion chromatogram of the supercritical fluid extract (SFE) of a fragment of the Orgueil meteorite. Structures for I to XIII are given in the Appendix; ^=n-alkane (n-C13À20), A=unknown A. Contaminants in Orgueil (Watson et al. 2003)

Origin of organic matter - contamination issues (from Hayatsu et al., 1973) U - 3.0 2.8 2.6 2.4 2.2 1000/T (?K-') a is defined as (3C/ 20 18 o),o2/(13C/12)..1 30 min 20 10 40 30 20 Fig. 4. Hydrocarbons from Murchison meteorite and Fischer-Tropsch synthesis; BP, branched paraffin;BO, branched olefin; ,I, phenyl radical. For additional peak iden- tifications, see (18). Of the 61 hydrocarbons in the meteorite, 42 (underlined) are also present in the Fischer-Tropschsample, though often not in comparable amount. (Solid area) Aromatic hydrocarbons, (stippled area) aliphatic hydrocarbons, (blank area) compoundscontainingCl or S. 784 impa sient shocks (1). Of cours temperature episodes mus pened early or on a local s mit survival of other, mo ture-sensitive compounds. Isoprenoid alkanes. At appeared (26) that nearly ceous chondrites contain th alkanes pristane and phytan tetramethylpentadecane an tetramethylhexadecane). Th drocarbons, which may regarded as tetramers o CH : C(CHa3)CH: CH2, logical markers on the derived mainly from the chain of the chlorophyl Their presence in meteorit gested either extraterrestri abiotic process that strongly prenoids over other types hydrocarbons (13, 41). It seems, however, th sults reflected terrestrial co Studier et al. (18) found n isoprenoids in Orgueil a only small amounts of dim noids from C9 to CI4. pounds can, however, be FTT syntheses (18); in f more prominent in synth than in meteorites (Fig SCIE

Fig. 1. Histograms illustrating the internal distributions of n-alkanes, pristane (Pr) and phytane (Ph) for the SFE extracts of the seven meteorite samples. 4.4. Vigarano (CV3) The Vigarano SFE extract contained n- 4.5. Allende (CV3) GC-MS analyses of the SFE extract of Allende n-alkanes in chondrites (Sephton, Pillinger & Gilmour 2001) Phytane - 2, 6, 10, 14 tetramethyl pentadecane

Fig. 1. Histograms illustrating the internal distributions of n-alkanes, pristane (Pr) and phytane (Ph) for the SFE extracts of the seven meteorite samples. 4.4. Vigarano (CV3) The Vigarano SFE extract contained n- 4.5. Allende (CV3) GC-MS analyses of the SFE extract of Allende n-alkanes in chondrites (Sephton, Pillinger & Gilmour 2001) Phytane - 2, 6, 10, 14 tetramethyl pentadecane

-2.01 IO 20 I)0 40 20 4.0 2.0 2.0 1.0 0 -1.0 -2.0 -2.0 -4.0 00 70 20 20 IOC sample. A large decrease in abundance n-alkane from C number 14 to 28. In decrease does not appear to be as pro component contributes substantially terior extract trace: a phthalate residue and anthracene at Cz,, and an unkno base peak at m/z 208 in the case of C amounts of n-alkanes in the interior or represent contamination that has di of the stone is not known. However, alkanes are indigenous, they are not t pounds, as has been previously claimed GC-MS Analyses of Hydrocarbon Ex Meteorite The Murray meteorite is very simi meteorite but has had a terrestrial e twice as long. (The Murray fall was i 1969.) Exterior and interior samples obtained by drilling, respectively, at th interior of a fragment that had been ob when a larger stone was broken. Benz of these samples were prepared and with Murchison specimen 2. Both ext dant n-alkanes along with clear indicati tamination in the form of isoprenoid esters. The distribution of the n-alkane interior sample is illustrated by the m matogram shown in Fig. 3. The maxim ion, which is very intense in the mass Exterior Exterior Murchison aliphatic hydrocarbons (Cronin & Pizzarello, 1990)

-2.01 IO 20 I)0 40 20 4.0 2.0 2.0 1.0 0 -1.0 -2.0 -2.0 -4.0 00 70 20 20 IOC sample. A large decrease in abundance n-alkane from C number 14 to 28. In decrease does not appear to be as pro component contributes substantially terior extract trace: a phthalate residue and anthracene at Cz,, and an unkno base peak at m/z 208 in the case of C amounts of n-alkanes in the interior or represent contamination that has di of the stone is not known. However, alkanes are indigenous, they are not t pounds, as has been previously claimed GC-MS Analyses of Hydrocarbon Ex Meteorite The Murray meteorite is very simi meteorite but has had a terrestrial e twice as long. (The Murray fall was i 1969.) Exterior and interior samples obtained by drilling, respectively, at th interior of a fragment that had been ob when a larger stone was broken. Benz of these samples were prepared and with Murchison specimen 2. Both ext dant n-alkanes along with clear indicati tamination in the form of isoprenoid esters. The distribution of the n-alkane interior sample is illustrated by the m matogram shown in Fig. 3. The maxim ion, which is very intense in the mass Exterior Exterior Murchison aliphatic hydrocarbons (Cronin & Pizzarello, 1990) Interior Interior

3s 30 25 s ’3 20 I.L 5; is IO 5 0 IC I.... I . . . . I . . . . I4 IS 20 25 30 Carbon t(umb~r FIG. 4. Norma1 alkane abundances in whole benzene-methanol extracts of the Murray meteorite: triangles, exterior sample, mainly fusion crust; circles, interior sample 1 taken from surface (after re- moval of fusion crust) to 1.2 cm; squares, interior sample 2 taken from 1.2cm to 2.5 cm below surface; hexagons, sum of exterior and two interior samples. x c 1.0 gE 0.5 f 0 50 IO0 nC13 4 TIYE bIlla. Eii m5 IL6 TIME (m FIG. 5. Single ion chromatograms of extract of an interior (1.2to 2.5 cm dep 149; (b) m/z 57. The isoprenoid alkan Murray n-alkanes (Cronin and Pizzarello, 1990)

3s 30 25 s ’3 20 I.L 5; is IO 5 0 IC I.... I . . . . I . . . . I4 IS 20 25 30 Carbon t(umb~r FIG. 4. Norma1 alkane abundances in whole benzene-methanol extracts of the Murray meteorite: triangles, exterior sample, mainly fusion crust; circles, interior sample 1 taken from surface (after re- moval of fusion crust) to 1.2 cm; squares, interior sample 2 taken from 1.2cm to 2.5 cm below surface; hexagons, sum of exterior and two interior samples. x c 1.0 gE 0.5 f 0 50 IO0 nC13 4 TIYE bIlla. Eii m5 IL6 TIME (m FIG. 5. Single ion chromatograms of extract of an interior (1.2to 2.5 cm dep 149; (b) m/z 57. The isoprenoid alkan Exterior 0-1.2 cm below surface Murray n-alkanes (Cronin and Pizzarello, 1990)

3s 30 25 s ’3 20 I.L 5; is IO 5 0 IC I.... I . . . . I . . . . I4 IS 20 25 30 Carbon t(umb~r FIG. 4. Norma1 alkane abundances in whole benzene-methanol extracts of the Murray meteorite: triangles, exterior sample, mainly fusion crust; circles, interior sample 1 taken from surface (after re- moval of fusion crust) to 1.2 cm; squares, interior sample 2 taken from 1.2cm to 2.5 cm below surface; hexagons, sum of exterior and two interior samples. x c 1.0 gE 0.5 f 0 50 IO0 nC13 4 TIYE bIlla. Eii m5 IL6 TIME (m FIG. 5. Single ion chromatograms of extract of an interior (1.2to 2.5 cm dep 149; (b) m/z 57. The isoprenoid alkan Fusion crust Exterior 0-1.2 cm below surface Murray n-alkanes (Cronin and Pizzarello, 1990)

3s 30 25 s ’3 20 I.L 5; is IO 5 0 IC I.... I . . . . I . . . . I4 IS 20 25 30 Carbon t(umb~r FIG. 4. Norma1 alkane abundances in whole benzene-methanol extracts of the Murray meteorite: triangles, exterior sample, mainly fusion crust; circles, interior sample 1 taken from surface (after re- moval of fusion crust) to 1.2 cm; squares, interior sample 2 taken from 1.2cm to 2.5 cm below surface; hexagons, sum of exterior and two interior samples. x c 1.0 gE 0.5 f 0 50 IO0 nC13 4 TIYE bIlla. Eii m5 IL6 TIME (m FIG. 5. Single ion chromatograms of extract of an interior (1.2to 2.5 cm dep 149; (b) m/z 57. The isoprenoid alkan Fusion crust Interior 1.2-2.5 cm below surface Exterior 0-1.2 cm below surface Murray n-alkanes (Cronin and Pizzarello, 1990)

M.A. Sephton et al. / Precambrian Research 106 (2001) 47–58 53 Fig. 2. Plot of d13 C values vs carbon number for individual n-alkanes from meteorite SFE extracts. Assignments are as follows: (open circle) Orgueil, (filled circle) Murchison, (filled diamond) Cold Bokkeveld, (filled square) Vigarano, (open diamond) Ornans, (open square) Bishunpur. The n-C13 to n-C16 measurements for Murchison are from Gilmour and Pillinger (1993). Values of Murchison aliphatic fractions are included for comparisons (Krishnamurthy et al., 1992), as are ranges of bulk petroleum (Stahl, 1979)) and petroleum n-alkanes (Bjorøy et al., 1991). in general agreement with the majority of the previous analyses performed on this meteorite. Earlier studies on the aliphatic hydrocarbons in Cold Bokkeveld have detected n-alkane distribu- Isotopic compositions of aliphatic hydrocarbons (data from Sephton et al., 2001; Gilmour & Pillinger, 1993)

M.A. Sephton et al. / Precambrian Research 106 (2001) 47–58 53 Fig. 2. Plot of d13 C values vs carbon number for individual n-alkanes from meteorite SFE extracts. Assignments are as follows: (open circle) Orgueil, (filled circle) Murchison, (filled diamond) Cold Bokkeveld, (filled square) Vigarano, (open diamond) Ornans, (open square) Bishunpur. The n-C13 to n-C16 measurements for Murchison are from Gilmour and Pillinger (1993). Values of Murchison aliphatic fractions are included for comparisons (Krishnamurthy et al., 1992), as are ranges of bulk petroleum (Stahl, 1979)) and petroleum n-alkanes (Bjorøy et al., 1991). in general agreement with the majority of the previous analyses performed on this meteorite. Earlier studies on the aliphatic hydrocarbons in Cold Bokkeveld have detected n-alkane distribu- Isotopic compositions of aliphatic hydrocarbons (data from Sephton et al., 2001; Gilmour & Pillinger, 1993) Murchison Orgueil Cold BokkeveldVigarano Ornans

M.A. Sephton et al. / Precambrian Research 106 (2001) 47–58 53 Fig. 2. Plot of d13 C values vs carbon number for individual n-alkanes from meteorite SFE extracts. Assignments are as follows: (open circle) Orgueil, (filled circle) Murchison, (filled diamond) Cold Bokkeveld, (filled square) Vigarano, (open diamond) Ornans, (open square) Bishunpur. The n-C13 to n-C16 measurements for Murchison are from Gilmour and Pillinger (1993). Values of Murchison aliphatic fractions are included for comparisons (Krishnamurthy et al., 1992), as are ranges of bulk petroleum (Stahl, 1979)) and petroleum n-alkanes (Bjorøy et al., 1991). in general agreement with the majority of the previous analyses performed on this meteorite. Earlier studies on the aliphatic hydrocarbons in Cold Bokkeveld have detected n-alkane distribu- Isotopic compositions of aliphatic hydrocarbons (data from Sephton et al., 2001; Gilmour & Pillinger, 1993) Murchison Orgueil Cold BokkeveldVigarano Ornans

using least-squares linear regression. Figure 4 illustrates this data and compares it to similar data from the CM2 Murch- ison meteorite and the Antarctic CR2 meteorites GRA 95229, EET 92042, and LAP 02342. The linear regression through the fungal peptide data in building block for peptaibols is produced by enzymatic methyl addition via adenosyl-methionine to L-Ala (Kubicek et al., 2007), our measurements suggest that this process causes enrichment in the a-AIB relative to the L-Ala, with d13 C values of a-AIB being enriched by 5–8%. Presumably, FIG. 4. Isotopic ratios and linear regression fits for d13 C for the pairs of amino acids (A) a-AIB vs. Gly, (B) L-Ala vs. Gly, and (C) a-AIB vs. L-Ala, and for d15 N for (D) a-AIB vs. Gly, (E) L-Ala vs. Gly, and (F) a-AIB vs. L-Ala. The data from the four fungal peptides analyzed in this work are represented by open squares (,). Meteoritic data from the CM2 Murchison meteorite () and the Antarctic CR2 meteorites GRA 95229 and LAP 02342 (~) are also shown (see Fig. 3 caption for references). Panel B also includes data from the CR2 meteorite EET 92042 (~) (Martins et al., 2007a). 130 ELSILA ET AL. Isotopic identification of potential contaminants (Elsila et al., 2011)

using least-squares linear regression. Figure 4 illustrates this data and compares it to similar data from the CM2 Murch- ison meteorite and the Antarctic CR2 meteorites GRA 95229, EET 92042, and LAP 02342. The linear regression through the fungal peptide data in building block for peptaibols is produced by enzymatic methyl addition via adenosyl-methionine to L-Ala (Kubicek et al., 2007), our measurements suggest that this process causes enrichment in the a-AIB relative to the L-Ala, with d13 C values of a-AIB being enriched by 5–8%. Presumably, FIG. 4. Isotopic ratios and linear regression fits for d13 C for the pairs of amino acids (A) a-AIB vs. Gly, (B) L-Ala vs. Gly, and (C) a-AIB vs. L-Ala, and for d15 N for (D) a-AIB vs. Gly, (E) L-Ala vs. Gly, and (F) a-AIB vs. L-Ala. The data from the four fungal peptides analyzed in this work are represented by open squares (,). Meteoritic data from the CM2 Murchison meteorite () and the Antarctic CR2 meteorites GRA 95229 and LAP 02342 (~) are also shown (see Fig. 3 caption for references). Panel B also includes data from the CR2 meteorite EET 92042 (~) (Martins et al., 2007a). 130 ELSILA ET AL. Isotopic identification of potential contaminants (Elsila et al., 2011) fungal peptaibiotics

using least-squares linear regression. Figure 4 illustrates this data and compares it to similar data from the CM2 Murch- ison meteorite and the Antarctic CR2 meteorites GRA 95229, EET 92042, and LAP 02342. The linear regression through the fungal peptide data in building block for peptaibols is produced by enzymatic methyl addition via adenosyl-methionine to L-Ala (Kubicek et al., 2007), our measurements suggest that this process causes enrichment in the a-AIB relative to the L-Ala, with d13 C values of a-AIB being enriched by 5–8%. Presumably, FIG. 4. Isotopic ratios and linear regression fits for d13 C for the pairs of amino acids (A) a-AIB vs. Gly, (B) L-Ala vs. Gly, and (C) a-AIB vs. L-Ala, and for d15 N for (D) a-AIB vs. Gly, (E) L-Ala vs. Gly, and (F) a-AIB vs. L-Ala. The data from the four fungal peptides analyzed in this work are represented by open squares (,). Meteoritic data from the CM2 Murchison meteorite () and the Antarctic CR2 meteorites GRA 95229 and LAP 02342 (~) are also shown (see Fig. 3 caption for references). Panel B also includes data from the CR2 meteorite EET 92042 (~) (Martins et al., 2007a). 130 ELSILA ET AL. Isotopic identification of potential contaminants (Elsila et al., 2011) fungal peptaibiotics Murchison

839 50 63 68 69 377 Mono, di & hydroxycarboxylic acids Sulfonic, phosphonic acids Amino & diamino acids & amines Hydrocarbons Dicarboximides Aldehydes, ketones, alcohols Purines, pyrimidines & pyrimidine carboxylic acid 8 6 6 6 20 58 Murchison Tagish Lake

Retention time 1 Retentiontime2 Structural diversity of Murchison SOM - GCxGC-TOF-MS (Wilson et al. in prep)

Structural diversity of Murchison methanolic extract (Schmitt-Kopplin et al. 2010)

such as Michael addition of ammonia to cyanoacetylene (Miller 1957). Based on this amino acid evidence it was concluded that the Orgueil and Ivuna meteorites must have originated on a chemically distinct parent body must also be accounted for when drawing comparisons between laboratories. Here for the first time we compare the relative abundances of amino acids collected on a suite of CI, CM, and CR carbonaceous chondrites 0 0.5 1 1.5 2 2.5 3 3.5 4 Orgueil SCO 06043 MET 01070 GRO 95577 Murchison LEW 90500 LON 94102 EET 92042 QUE 99177 CI1 CM1 CR1 CM2 CR2 -Alanine -Alanine -Aminoisobutyric acid (AIB) Isovaline CR3 RelativeAbundance Fig. 4. A comparison of the relative molar abundances (glycine = 1.0) of alanine, b-alanine, a-aminoisobutyric acid, and isovaline in the 6M HCl-hydrolyzed, hot-water extracts of the carbonaceous meteorites investigated in this study. The relative abundances were calculated from the data in Table 2 after correcting for the molecular weights of each amino acid. The uncertainties were calculated by standard error propagation of the absolute errors in Table 2. The amino acid data for Murchison (USNM 6650) and LEW 90500 were taken from Glavin et al. (2006). Amino acids in carbonaceous chondrites 1963 Evidence for parent body processing of amino acids (Glavin et al., 2011) more primitivemore altered

Purine, 2,6-diam biguously identified Murchison by thei mass spectrum (inc ple fragmentation p sulting in the detec different formic ac three different liqu ments (one triple q laboratories [Natio (NASA) Goddard which all produced were identified (by accurate mass meas meteorites as well both purine and 6,8 bonaceous chondri and provides addit teorites are indigen from one report o S-2L (23), these th biology. Studies of apeutic, have show scription by multipl diaminopurine (8-a to be the result of Fig. 1. Distribution of guanine, hypoxanthine, xanthine, adenine, purine, and 2,6-diaminopurine in 11 carbonaceous chondrites and one ureilite. The three CM2 carbonaceous chondrites in this study (Murchison, LEW 90500, and LON 94102) contained significantly higher (approximately 4× to 12×) abundances of purine nucleobases as well as greater structurally di- versity. The * represents a tentative assignment. The meteorites are roughly ordered by increasing aqueous alteration (Right to Left) as determined using mineralogical and isotopic evidence (38–41). The relative degree of aqueous alteration among carbonaceous chondrites within the same group and of the Nucleobases in meteorites (Callahan et al., 2011)

Structural diversity of Murchison methanolic extract (Schmitt-Kopplin et al. 2010)

Deuterium enrichments in amino acids (Data from Pizzarello & Huang, 2005; Pizzarello et al., 2008) 0 1000 2000 3000 4000 5000 6000 7000 8000 δ2HVSMOW (‰) 0 5 10 15 Frequency Murchison GRA95229

Nitrogen in CR chondrites (Pizzarello & Homes, 2009) GRA 95229 90 100 110 120 130 140 δ15NAIR (‰) 0 1000 2000 3000 4000 5000 6000 7000 8000 δ2HVSMOW(‰) 2-H 2-methyl

Nitrogen in CR chondrites (Pizzarello & Homes, 2009) GRA 95229 90 100 110 120 130 140 δ15NAIR (‰) 0 1000 2000 3000 4000 5000 6000 7000 8000 δ2HVSMOW(‰) 2-H 2-methyl

Nitrogen in CR chondrites (Pizzarello & Homes, 2009) GRA 95229 90 100 110 120 130 140 δ15NAIR (‰) 0 1000 2000 3000 4000 5000 6000 7000 8000 δ2HVSMOW(‰) 2-H 2-methyl

isotopes between compounds rather than thermodynamic equilibrium (Gilmour and Pillinger, 1994; Naraoka et al., 2000). The d13 C values. This has led to the suggestion the synthetic processes that led to mation, isotopic fractionation was a extreme, implying that synthesis took low-temperature environment such as space (Sephton and Gilmour, 2000). T heterogeneity displayed by aromatic c in Murchison and Asuka-881458 contain evidence for different synthetic There is a 7.5‰ difference in d1 between PAHs isomers containing a fi ring (e.g., fluoranthene) and those wi pyrene), which has been interpreted a of two possible pathways for the fo PAHs (Gilmour and Pillinger, 1994 et al., 2000). The d13 C values for the C12–C26 from six chondrites are shown in (Sephton et al., 2001). None of the exhibit either the 13 C-enrichments or isotopic trends that apparently charact genous organic matter in meteorites. M d13 C values are similar both in value trends shown within homologous seri variations observed for terrestrial products or other terrestrial fossil hyd These features confirm the long-held that these molecules are contaminant 35 30 25 20 15 10 5 0 –5 0 1 2 3 4 5 6 hydrocarbons carboxylic acids amino acids d13 C(‰) Carbon number Figure 2 Carbon stable-isotope compositions of low- molecular-weight hydrocarbons, amino acids, and monocarboxylic acids from the Murchison meteorite plotted against carbon number. Carbon number 1 denotes methane and CO2, 2 denotes ethane, ethanoic acid, glycine, etc. (source Yuen et al., 1984). Molecular level isotope analysis - LMW compounds Murchison (Yuen et al., 1984)

isotopes between compounds rather than thermodynamic equilibrium (Gilmour and Pillinger, 1994; Naraoka et al., 2000). The d13 C values. This has led to the suggestion the synthetic processes that led to mation, isotopic fractionation was a extreme, implying that synthesis took low-temperature environment such as space (Sephton and Gilmour, 2000). T heterogeneity displayed by aromatic c in Murchison and Asuka-881458 contain evidence for different synthetic There is a 7.5‰ difference in d1 between PAHs isomers containing a fi ring (e.g., fluoranthene) and those wi pyrene), which has been interpreted a of two possible pathways for the fo PAHs (Gilmour and Pillinger, 1994 et al., 2000). The d13 C values for the C12–C26 from six chondrites are shown in (Sephton et al., 2001). None of the exhibit either the 13 C-enrichments or isotopic trends that apparently charact genous organic matter in meteorites. M d13 C values are similar both in value trends shown within homologous seri variations observed for terrestrial products or other terrestrial fossil hyd These features confirm the long-held that these molecules are contaminant 35 30 25 20 15 10 5 0 –5 0 1 2 3 4 5 6 hydrocarbons carboxylic acids amino acids d13 C(‰) Carbon number Figure 2 Carbon stable-isotope compositions of low- molecular-weight hydrocarbons, amino acids, and monocarboxylic acids from the Murchison meteorite plotted against carbon number. Carbon number 1 denotes methane and CO2, 2 denotes ethane, ethanoic acid, glycine, etc. (source Yuen et al., 1984). Molecular level isotope analysis - LMW compounds Murchison (Yuen et al., 1984)

-30 -24 -18 -12 -6 0 6 12 0 2 4 6 8 10 Molecular level isotope analysis - monocarboxylic acids in Murchison (Huang et al., 2007) δ13CVPDB/‰ carbon number

-30 -24 -18 -12 -6 0 6 12 0 2 4 6 8 10 Molecular level isotope analysis - monocarboxylic acids in Murchison (Huang et al., 2007) δ13CVPDB/‰ carbon number

These features confirm the long-held suspicion that these molecules are contaminants from the –5 –10 –15 –20 –25 –30 d13 C(‰) Carbon number 5 10 15 20 25 Murchison A-881458 Figure 3 Carbon stable-isotope compositions of solvent extractable aromatic and PAHs plotted against carbon number from the Murchison and Asuka-881458 CM2 carbonaceous chondrites (sources Yuen et al., 1984; Gilmour and Pillinger, 1994; Sephton et al., 1998; Naraoka et al., 2000). plotted against carbon number. Carbon number 1 denotes methane and CO2, 2 denotes ethane, ethanoic acid, glycine, etc. (source Yuen et al., 1984). –15 –20 –25 –30 –35 –40 d13 C(‰) Carbon number 10 15 20 25 30 Orgueil Tagish Lake Cold bokkeveld Murchison Vigarano Ornans Figure 4 Carbon stable-isotope compositions of solvent extractable n-alkanes from the Orgueil (CI), Cold Bokkeveld (CM2), Murchison (CM2), Vigarano (CV3), Ornans (CO), and Tagish Lake carbonaceous chondrites plotted against carbon number (sources Sephton et al., 2001; Pizzarello et al., 2001).

These features confirm the long-held suspicion that these molecules are contaminants from the –5 –10 –15 –20 –25 –30 d13 C(‰) Carbon number 5 10 15 20 25 Murchison A-881458 Figure 3 Carbon stable-isotope compositions of solvent extractable aromatic and PAHs plotted against carbon number from the Murchison and Asuka-881458 CM2 carbonaceous chondrites (sources Yuen et al., 1984; Gilmour and Pillinger, 1994; Sephton et al., 1998; Naraoka et al., 2000). plotted against carbon number. Carbon number 1 denotes methane and CO2, 2 denotes ethane, ethanoic acid, glycine, etc. (source Yuen et al., 1984). –15 –20 –25 –30 –35 –40 d13 C(‰) Carbon number 10 15 20 25 30 Orgueil Tagish Lake Cold bokkeveld Murchison Vigarano Ornans Figure 4 Carbon stable-isotope compositions of solvent extractable n-alkanes from the Orgueil (CI), Cold Bokkeveld (CM2), Murchison (CM2), Vigarano (CV3), Ornans (CO), and Tagish Lake carbonaceous chondrites plotted against carbon number (sources Sephton et al., 2001; Pizzarello et al., 2001).

ative with the abundance of hydrated including D- and 15 N-rich IOM that is best pre- opic com- onocarbox- he Tagish Uncertain- e standard hree injec- ample. For with low h as those r decanoic a value of based on achieved run with ions. Also he results Murchison lic acids. flects relative concentration (13). onJuly6,2011www.sciencemag.orgownloadedfrom Tagish Lake monocarboxylic acids (Herd et al., 2011)

Pizzarello et al.: Organic Material in Carbonaceous Chondrites and IDPs 641 Fig. 4. Possible reaction pathways in the formation of meteoritic PAHs. (1) naphthalene, (2) biphenyl, (3) acenaphthene, (4) anthra- cene, (5) 1-phenyl naphthalene, (6) phenanthrene, (7) fluoranthene, (8) benz(a)anthracene, (9) benzo(ghi)fluoranthene, (10) triphenylene, (11,13,15) benzofluoranthenes, (12) crysene, (14) pyrene, (16,17) benzopyrenes, (18) perylene, (19) benzo(ghi)perylene. Re-drawn from Naraoka et al., 2000. Pathways of condensation (Naraoka et al. 2000)

p : solenoïd + electric control Sample tube Fig. 1. Oxidation apparatus for organic solid residues. Oxygen supply is ensured by the left part of the line. The oxidation occurred in the quartz reaction tube under oxygen atmosphere at temperature above 1000 K. U-trap allowed the separation of CO2 from H2O and sample tube received pure CO2 for analysis on the mass spectrometer (not represented there). See text for comments. r are re- ollows: (1) and the 2 CPDB = ore irra- position samples on 13 C een 0.32 between rrespond er sealed residues e carbon on of the 0.0 1.41.21.00.80.60.40.2 -31 -30 -29 -28 -27 -26 -25 -24 1/ quantity (1/µmoles) δ13C(‰) Blank -40 -39 METHANE Fig. 2. 13 C (in ) versus 1/Q (Q in 1/µmoles) in organic residues re- sulting from irradiation of methane ices. Error bars are due to the blank contribution. The initial isotopic composition of methane is also shown. The decrease in 13 C with sample size is interpreted as a progressive maturation by sputtering of initial polymers having 13 C values close 1178 C. L´ecluse et al.: Carbon is (CH )4 n CH3 CH3CH2 -40‰ -24‰ δ C 13 C Hi j < -40‰ C Hi j > -24‰ -35‰ p p Fig. 3. Flow chart depicting the irradiation model described by Eqs. (1) to (7) (see text). The carbon isotopic composition of each species is indicated in 13 C . The species cij are outgassed form the solid during irradiation. Methane and the other organic compounds remain as solid phases during irradiation. Carbon isotopic fractionation in methane ice irradiation (Lecluse et al. 1998)

1994MNRAS.269..235G Pathways of condensation (Gilmour & Pillinger, 1994)

-500 0 500 1000 1500 2000 2500 -50 -25 0 25 50 75 100 δ13CVPDB / ‰ δ2HVSMOW/‰ amino acids sulfonic acids hydrocarbons polar hydrocarbons carboxylic acids volatile hydrocarbons

3.4. Comparison with IOM stru and other thermal and chemica Many studies have demons carbonaceous chondrites is com and aliphatic units. Direct obs solid state 1 H and 13 C NMR in variably condensed aromatic cor linkages (Cronin et al., 1987). found 8 different types of carb cally and aliphatically linked C linked to heteroelements, proton ed aromatic C, carboxyl and carb CP/MAS 13 C NMR spectroscop the percentage of aromatic carb 67%) and Orgueil (69–78%) ( Their data also suggest a high le aliphatic side chains, especially and co-workers using combine meteorites with different class CR2) further found a much wi groups, and showed that aromat substituted by aliphatic side ch branching (Cody et al., 2002; 2005). Cody and Alexander su low temperature chemical oxid Fig. 3. The GC-FID traces of the monocarboxylic acids derived from RuO4 oxidation of IOM (A), and direct water extraction of 522 Y. Huang et al. / Earth and Planetary Science Letters 259 (2007) 517–525 Monocarboxylic acids released by RuO4 oxidation of IOM (Huang et al., 2007)

δ13CVPDB / ‰ δ2HVSMOW/‰ Monocarboxylic acids released by RuO4 oxidation of IOM (Huang et al., 2007) -450 0 450 900 1350 1800 -60 -45 -30 -15 0 15 SOM IOM

Fig. 4. Murchison PAH, the most abundant type of extraterrestrial organic compound in both meteorites and space. 2500 Murchison organic matter volatile bases carboxylic acids sulfonic acids macromolecular material hydrocarbons Terrestrial organic matter coal and petroleum marine organisms nonmarine organisms methane to −110 polar hydrocarbons volatile hydrocarbons amino acids2000 1500 1000 500 −500 −1000 −70 −60 −40 −20 δ13C (‰) δD (‰) 0 20 40 0 Fig. 5. The distinction between stable carbon and hydrogen isotope ratios in Murchison and life. The difference allows abiogenic extraterrestrial organic matter to be distinguished from its terrestrial biological counterpart. The abundances of stable isotopes are expressed using the d notation. These indicate the difference, in per mil (ø), between the relevant ratio in the sample and the same ratio in an

Naphthalene alkylation vs. petrologic type (Elsila et al., 2005) appears between extent of aqueous alteration and naphthalene alkylation pattern in our measurements, at least for those me- teorites for which we have information on aqueous exposure; the most aqueously altered CM2 meteorites have the highest amount of naphthalene alkylation. Figure 2C presents the degree of naphthalene alkylation for al., 1995), and both meteorites show evidence of oxidation (McSween, 1977). These two meteorites have high amounts of alkylation, with alkylated naphthalene compounds being more abundant than unalkylated naphthalene. The Allende meteorite contains higher levels of naphthalene alkylation than any other meteorite studied in this work. The third meteorite displayed, Fig. 2. Naphthalene alkylation distributions for four sets of carbonaceous chondrites. The symbols C1, C2, and C3 represent mono-, di-, and trialkylated naphthalene. 1352 J. E. Elsila et al. appears between extent of aqueous alteration and naphthalene alkylation pattern in our measurements, at least for those me- teorites for which we have information on aqueous exposure; the most aqueously altered CM2 meteorites have the highest amount of naphthalene alkylation. Figure 2C presents the degree of naphthalene alkylation for four non-CM2 carbonaceous chondrites that also underwent aqueous alteration. The meteorite GRA 95229 shows a degree of naphthalene alkylation similar to that of the meteorites displayed in Figure 2A, with an inverse correlation between abundance and alkylation. This CR2 meteorite has seen mod- erate aqueous alteration (Weisberg et al., 1993). The ungrouped C2 meteorite MAC 88107 has high abundances of C1- and C2-naphthalene, similar to the meteorites in Figure 2B, but low levels of C3-naphthalene, similar to those in Figure 2A. The Tagish Lake meteorite, also an ungrouped C2 chondrite (Zo- lensky et al., 2002), has relatively high amounts of alkylation, as does the Orgueil (CI1) meteorite sample, which has been al., 1995), and both meteorites show evidence (McSween, 1977). These two meteorites have high alkylation, with alkylated naphthalene compounds abundant than unalkylated naphthalene. The Allen contains higher levels of naphthalene alkylation th meteorite studied in this work. The third meteori ALH 83108, is classified CO3, and reveals moder of alkylated naphthalene compounds that decreas tration with increasing alkylation. Four analyzed meteorites are not displayed because they had undetectable levels of naphth derivatives. The ␮L2 MS spectra of the three CK analyzed (ALH 85002, EET 92002, and Karoond ingly different from all other carbonaceous chond but show similarities to each other (Fig. 3). The monly detected in meteorites (e.g., naphthalene, p pyrene) were not observed, although other uniden were seen at 135 Da, 179 Da, and 250 Da. The pre Fig. 2. Naphthalene alkylation distributions for four sets of carbonaceous chondrites. The symbols C1, C2, and C represent mono-, di-, and trialkylated naphthalene. 1352 J. E. Elsila et al.

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