amino acid composition, petrology, geochemistry, c ......petrology and chemistry analysis the...

1581 copy The Meteoritical Society 2007 Printed in USA

Meteoritics amp Planetary Science 42 Nr 9 1581ndash1595 (2007)Abstract available online at httpmeteoriticsorg

Amino acid composition petrology geochemistry 14C terrestrial ageand oxygen isotopes of the Shiintr 033 CR chondrite

Z MARTINS1dagger B A HOFMANN2 E GNOS3 R C GREENWOOD4 A VERCHOVSKY4 I A FRANCHI4 A J T JULL5 O BOTTA6 7daggerdagger D P GLAVIN6 J P DWORKIN6 and P EHRENFREUND1

1Astrobiology Laboratory Leiden Institute of Chemistry 2300 RA Leiden The Netherlands 2Naturhistorisches Museum der Burgergemeinde Bern CH-3005 Bern Switzerland

3Institute of Geological Sciences CH-3012 Bern Switzerland4Planetary and Space Sciences Research Institute Open University Milton Keynes MK7 6AA UK

5University of Arizona NSF-Arizona Accelerator Mass Spectrometry Laboratory Tucson Arizona 85721 USA6NASA Goddard Space Flight Center Goddard Center for Astrobiology Greenbelt Maryland 20771 USA

daggerPresent address Department of Earth Science and Engineering South Kensington Campus Imperial College London London SW7 2AZ UK

daggerdaggerPresent address International Space Science Institute 3012 Bern SwitzerlandCorresponding author E-mail zmartinsimperialacuk

(Received 30 August 2006 revision accepted 30 March 2007)

AbstractndashWe have analyzed Shiintr 033 a CR chondrite from the Omani desert using several differentanalytical techniques designed to study the degree of terrestrial alteration of this meteorite and also itspetrologic classification Bulk chemical analyses (including organic carbon and mean total H2Ocontent) are consistent with a CR classification Additionally oxygen isotope analysis on a bulksample indicates that Shiintr 033 is of type CR2 Amino acid analysis using liquid chromatography withUV fluorescence detection (HPLC-FD) and liquid chromatography-time of flight-mass spectrometry(LC-ToF-MS) show that the absolute and the relative amino acid content of Shiintr 033 is distinct fromother carbonaceous chondrites Oxygen isotope analysis of a phyllosilicate-rich dark inclusion showsthat this inclusion is closer to CV3 or CO3 chondrites The effects of terrestrial weathering in Shiintr033 are evident from the dark inclusion carbon isotopic data bulk chemistry (through the elevatedconcentrations of Sr and Ba) and amino acid data which suggests extensive amino acidcontamination of the meteorite from the fall site soil Nevertheless Shiintr 033 contains a small fractionof indigenous components as indicated by the presence of the extraterrestrial amino acidα-aminoisobutyric acid (AIB) that was not detected in the Shiintr soils Finally the terrestrial age ofShiintr 033 was determined and is discussed in the context of high levels of contamination

INTRODUCTION

Hot deserts (including Australia western USA NorthAfrica and the Arabian Peninsula) have become a source ofan increasing number of meteorite finds in the past years(Jull et al 1990 Ash and Pillinger 1995 and references givenBischoff and Geiger 1995 Al-Kathiri et al 2005) Themeteorites collected in these arid areas suffer physical andchemical alterations ie weathering These terrestrialalteration effects were studied previously by other authorsand several different techniques were used to quantify theweathering degree For example the degree of oxidation inmeteorites as well as changes in the isotopic and chemicalcompositions were determined using among other

techniques 57Fe Moumlssbauer spectroscopy atomic emissionspectrometry (ICP-AES) stepped combustion analysisevolved gas analysis X-ray fluorescence spectroscopy(XRF) electron probe analysis (EPMA) backscatteredelectron spectrometry (BSE) and mass spectrometry (ICP-MS) (Ash and Pillinger 1995 Bland et al 1996a 1996b1998a 1998b Franchi et al 1996 Gillet et al 2005 Lee andBland 2004 Stelzner and Heide 1996 Stelzner et al 1999)

In this study an interdisciplinary team of researchersanalyzed the Shiintr 033 meteorite Shiintr 033 is the first CRcarbonaceous chondrite to be recovered from the Omanidesert (in October 2002) A unique feature of Shiintr 033 is thepresence of millimeter-sized dark inclusions that were thoughtto be similar to CI-type carbonaceous chondrites (Russell

1582 Z Martins et al

et al 2004) The goals of this study were to investigate howterrestrial alteration has changed the organic chemicalmineralogical and isotopic composition of the meteorite aswell as the dark CI-like inclusions Hence major and traceelements iron and volatiles abundances were obtained for theShiintr 033 meteorite In addition amino acid abundances ofShiintr 033 were measured and compared to 1) CM- and CI-type carbonaceous chondrites 2) two ordinary chondritescollected in the same area and 3) desert soil samples collectedon the proximities of the meteorite fall site location We havealso investigated the oxygen and carbon isotopes of Shiintr 033and compared these values to other meteorite classes Finallywe have also determined the terrestrial ages of Shiintr 033 andof the two ordinary chondrites collected in the Omani desertand have investigated their relationship to the extent ofterrestrial contamination

MATERIALS AND METHODS

Samples and Sample Preparation

Shiintr 033 (a CR chondrite) Shiintr 031 and Shiintr 035(both L6 chondrites) and three soil samples (named 78 82and 89) were collected in Oman (Fig 1) by a joint meteoritesearch program (Al-Kathiri et al 2005) Shiintr 033 consists of65 fragments with a total mass of 1098 g recovered from anarea of a few square meters A large Shiintr 033 meteoritefragment (2499 g) was selected for analysis and interiormaterial was obtained by removing the surface The interiorfragment was then crushed followed by removal of metal

nodules and chondrules hand-picked using flamed tweezersto enrich the phyllosilicate-rich material This enrichedmaterial (fines fraction) was homogenized into powder (486g) and used for the amino acids and oxygen isotopes analysisIndividual phyllosilicate-rich dark inclusions were selectedfor oxygen and carbon isotope analysis as well as individualchondrules picked from the coarse material for the oxygenisotope analysis A large piece of Murchison meteorite(6294 g USNM 6650) was provided by the SmithsonianNational Museum of Natural History Washington DCUSA Orgueil meteorite (776 g) was provided by the MuseacuteeNational drsquoHistoire Naturelle Paris France The MurchisonOrgueil Shiintr 031 and Shiintr 035 meteorites together with thethree soil samples (78 82 and 89) were separately ground andhomogenized into powder using a ceramic mortar and pestlein a glovebox containing argon They were stored in sterilizedglass vials before being analyzed A serpentine (hydratedmagnesium silicate) sample provided by the Natural HistoryMuseum Bern Switzerland was crushed into powder in thesame glove box heated to 500 degC for 3 hr prior to analysissubjected to the same processing procedure as the meteoritesand soil samples and used as a procedural blank

Powdered aliquots of Tiffa 001 (an H5 with weatheringdegree W2) and Grein 003 (an H6 with weathering degreeW1) collected in the Tenere region of Niger were used in ourstudy (for the oxygen isotope analysis) to test the efficiency ofthe ethanolamine-thioglycollate washing method (Cornishand Doyle 1984) in removing terrestrial weathering productsand their effects on the indigenous oxygen isotopiccomposition of the meteorite samples

Fig 1 Map showing the fall site of Shiintr 031 Shiintr 033 and Shiintr 035 meteorites and the places where the soil samples were collected herenamed 78 82 and 89 The inset shows the map of part of Oman bordered by the Arabian Sea One degree is about 111 km

The Shiintr 033 CR chondrite 1583

Chemicals Reagents and Tools

Amino acid standards (except D- and L-isovaline)sodium acetate trihydrate sodium borate decahydrateHPLC-grade water o-phthaldialdehyde (OPA) and N-acetyl-L-cysteine (NAC) were purchased from Sigma-AldrichAmmonium hydroxide (28ndash30 wt) and D- and L-isovalinestandards were purchased from Acros Organics Methanol(absolute HPLC) was acquired from Biosolve Ltd sodiumhydroxide and hydrochloric acid (37) from Boom and AG50W-X8 cation exchange resin (100ndash200 mesh) fromBio-Rad All tools glassware and ceramics used in theamino acid analysis were sterilized by annealing in aluminumfoil at 500 degC for 3 hr All tips and Eppendorf tubes used inthe same analysis were supplied sterilized from Sigma-Aldrich

Petrology and Chemistry Analysis

The petrology of Shiintr 033 was investigated using apolished thin section of 59 cm2 surface with transmitted andreflected light microscopy Mineral compositions weredetermined using a Cameca SX-50 microprobe equipped withwavelength-dispersive spectrometers using natural andsynthetic mineral standards and beam conditions of 15 kV and20 nA Data were corrected using the PAP procedure(Pouchou and Pichoir 1994) Cathodoluminescence (CL)images (Fig 2) were obtained using a high-sensitivity CLmicroscope (Ramseyer et al 1989) equipped with acomputer-controlled digital camera system (ColorView 12run under analySIS FIVE image analysis program) Beamconditions applied were 02ndash04 microAmm2 and 25 keV Ironhydroxides were removed from certain sample fractions for

oxygen isotope (see the Oxygen and Carbon Analysis section)and iron analyses using ethanolamine thioglycollate insolution with an equal volume of isopropanol to reduceviscosity and prevent precipitation of Fe-complexes Sampleswere leached until the production of the red iron complexceased which indicated that all iron hydroxides weredissolved and then washed in deionized water This treatmentremoves iron oxides hydroxides and metallic iron but notsilicate-bound iron

The bulk chemistry analysis was performed by lithiummetaboratetetraborate fusion and a combination ofinductively coupled plasmandashoptical emission spectroscopy(ICP-OES for major elements reported in wt) andinductively coupled plasmandashmass spectrometry (ICP-MS fortrace elements reported as ppm analysis code 4lithoresearch) Bulk iron was determined using ICP-OES andthe total carbon and CO2 were determined by combustioninfrared detection using oxygen and an inert gas respectivelyThe organic carbon is obtained by difference

Amino Acid Extraction Procedure HPLC-FD andLC-ToF-MS Analysis

Approximately 100 mg each of Shiintr 033 Shiintr 031Shiintr 035 Murchison and Orgueil meteorites together withShiintr landing site soil samples (named 78 82 and 89) and aserpentine control blank were analyzed using the establishedprocedure for extracting separating and analyzing aminoacids in meteorites (Zhao and Bada 1995 Botta et al 2002Glavin et al 2006) Each of these powdered samples wasflame-sealed inside a test tube (20 times 150 mm) together with1 ml of HPLC water and heated for 24 hr in a heating block(temperature set at 100 degC) After the hot water extraction the

Fig 2 Cathodoluminescence (CL) image of a polished thin section of Shiintr 033 showing the unequilibrated nature expressed by coexistingyellow red greenish and blue CL colors of chondrule minerals and glass Field of view is 38 mm

1584 Z Martins et al

test tubes were rinsed with HPLC water cracked open andcentrifuged One of two equal parts of the water supernatantswas then transferred to a smaller tube (10 times 75 mm) driedunder vacuum flame-sealed inside a test tube (20 times 150 mm)containing 1 ml of 6 N HCl and subjected to acid vaporhydrolysis for 3 hr at 150 degC The test tubes were then rinsedwith HPLC water and cracked open the small tubes wereremoved and dried under vacuum The hydrolyzed extractswere brought up in 3 ml of HPLC water desalted on a cationexchange resin and the amino acids eluted from the resinwith 5 ml of 2 M ammonium hydroxide These eluates weredried under vacuum and derivatized (Zhao and Bada1995) with o-phthaldialdehydeN-acetyl-L-cysteine (OPANAC) separately first at the Leiden Institute of Chemistry andthen at NASA Goddard At the Leiden Institute of Chemistrythe dried ammonium hydroxide eluates were brought up in100 microl HPLC water and 10 microl aliquots were added to 10 microl of01 M sodium borate buffer in Eppendorf vials These weredried under vacuum to remove any residual ammoniabrought up in 20 microl of sodium borate buffer and thenderivatized with 5 microl of OPANAC The derivatization wasquenched after 1 or 15 min by adding 475 microl of 50 mMsodium acetate buffer (mobile phase) At NASA Goddardthe same extracts were derivatized using the same procedureand then quenched after 1 or 15 min with 75 microl of 01 Mhydrazine hydrate OPANAC amino acid derivatives wereanalyzed by HPLC-FD at the Leiden Institute of Chemistryand by simultaneous HPLC-FD and ToF-MS at NASAGoddard HPLC-FD analysis was carried out in a C18 reversephase (250 times 46 mm) Synergi 4micro Hydro-RP 80A column(from Phenomenex) flow rate 1 mlmin and UVfluorescence detection on a Shimadzu RF-10AXL (excitationwavelength at 340 nm and emission at 450 nm) Theconditions for amino acid separations for the mobile phase at25 degC were as follows Buffer A was 50 mM sodium acetatecontaining 4 methanol (vv) buffer B was methanol Thegradient used was 0 to 4 min 0 buffer B 4 to 5 min 0 to20 buffer B 5 to 10 min 20 buffer B 10 to 17 min 20 to30 buffer B 17 to 27 min 30 to 50 buffer B 27 to37 min 60 buffer B 37 to 49 min 60 buffer B 49 to 50min 60 to 0 buffer B 50 to 60 min 0 buffer B Aminoacids were identified by comparison of retention time withknown standards LC-ToF-MS analyses were carried outaccording to the procedures described by Glavin at al (2006)In all analyses the amino acid abundances (part per billion byweight) in the samples were calculated by comparing theintegrated peak area corrected for the abundances in theserpentine blank sample with the integrated peak area ofknown amino acid standards

Oxygen and Carbon Analysis

Oxygen isotope analyses were performed on foursamples of the Shiintr 033 meteorite a whole rock sample

(WR) a whole rock sample washed in ethanolaminethioglycollate (washed WR) a composite of hand-pickedchondrules and a hand-picked phyllosilicate-rich inclusion(D) In addition powdered aliquots of the Tiffa 001 meteoriteand the Grein 003 meteorite were washed in ethanolaminethioglycollate (see the Petrology and Chemistry Analysissection for more details) until the solution barely changedcolor rinsed first in water then in isopropanol and driedbefore analysis

Oxygen isotopic analysis was done by laser fluorinationSamples of 1 to 2 mg of powdered material were heated witha CO2 laser (106 microm) in the presence of approximately 200torr of BrF5 The oxygen gas liberated was purifiedcryogenically and chemically before analysis on a PRISM III(VG Micromass UK) dual inlet mass spectrometerAnalytical precision is plusmn008permil for δ18O and plusmn004permil forδ17O Details of the method are given by Miller et al (1999)

Carbon isotope measurements were performed on thephyllosilicate-rich dark inclusion (D) A sample of 0423 mgof crushed material was step combusted in 50 degC and 100 degCincrements the gas at each heating step purified and theabundance and isotopic composition of carbon (as CO2)measured using a modified SIRA 24 (VG Micromass UK)redesigned to operate in static vacuum mode The system isreadily capable of analyzing less than 1 nmole of carbon witha precision of approximately plusmn1permil for δ13C Details of theanalytical technique are given by Wright and Pillinger(1989)

Terrestrial Age Analysis

The terrestrial ages of the Shiintr 033 Shiintr 031 and Shiintr035 meteorites (see Table 10 for the samples mass) weredetermined by accelerator mass spectrometry (AMS) ofcosmic rayndashproduced 14C Untreated and acid-etched (used toremove any weathering products) samples as well as asample of Shiintr 033 treated both by acid etching and withethanolamine thioglycollate (used to remove iron hydroxidesas discussed earlier) were measured Additional sampletreatment included preheating to 500 degC in air to removeterrestrial organic contaminants followed by fusion of thesample with iron using RF furnace heating in oxygen toproduce CO2 Further sample preparation 14C extraction andAMS measurement procedures are described elsewhere (Jullet al 1989 1990 1993 1998)

RESULTS AND DISCUSSION

Petrology

Shiintr 033 was classified as a CR chondrite (Russell et al2004) based on the reduced character of silicates (olivine withFa2ndash79 by electron microprobe Fe-poor pyroxene Fs12ndash121)and the presence of phyllosilicate-rich inclusions

The Shiintr 033 CR chondrite 1585

Representative olivine and pyroxene analyses performedin this study are listed in Table 1 A low metamorphic grade (3or lower) is supported by cathodoluminescence images(Fig 2) showing a heterogeneous and unequilibrated textureThis is spectacularly expressed by the bright yellow redgreenish and blue chondrule minerals and glass under thecathode Many chondrules show abrupt or gradual colorzoning The luminescence activity of enstatite and forsterite iscaused by traces of Cr and Mn (eg Steele et al 1990) Athigher metamorphic grades the cathode luminescence colorsare suppressed by the higher iron contents in forsterite andenstatite The average chondrule size of the PO POP PP BOand RP chondrules is 10 mm and the matrixchondrule +aggregate ratio is 053 Large metal grains and metal-rich POchondrules are common

Shiintr 033 contains lt10 vol dark soft inclusions up to5 mm in size that were originally classified as CI (Russellet al 2004) These inclusions show the presence of smectitic(possible smectite-chlorite mixed-layer clay minerals)phyllosilicates in XRD-patterns (peak at ~15 Aring) In polishedthin sections laths of pyrrhotite up to 60 microm in length andmicrometer-sized magnetite forming framboids of 5ndash10 micromin diameter are the major coarse phases in a fine-grainedmatrix rich in phyllosilicates bearing a similarity to CI matrixrather than to CM and CO matrices These phyllosilicate-richinclusions clearly correspond to the dark inclusions (DI) inCRs described by Weisberg et al (1993) both in terms ofmineralogy and mode of occurrence According to Weisberget al (1993) the DI are essentially identical to the matrix ofCR in mineralogy and composition The average composition(Table 8 in Weisberg et al 1993) is close to CI (except for Kand S)

The meteorite shows minor weathering of the metal (W2)but this is based only on limited alteration of metallic ironHowever iron hydroxides released during weatheringimpregnate the meteorite including the dark inclusions givingthe meteorite a generally yellow-brown rusty appearance

Chemistry

Bulk chemistry data were obtained on two bulk samples(from which some large metal nuggets were excluded due togrinding problems) and on the fraction of fines used foramino acid analysis (Table 2) Data for volatiles (C CO2 andH2O) are presented in Table 3 Data obtained on Shiintr 033are compared with CR analyses discussed in Bischoff et al(1993) Shiintr 033 has a bulk composition very similar to theaveraged CR chondrites (Table 2) The slightly lower ironcontent might be due to the exclusion of some large metalnuggets Compared with bulk analyses the fines fraction ofShiintr 033 used for amino acid analysis is slightly enriched iniron and volatiles including organic carbon and is slightlydepleted in Mg but is close in composition to the bulkmeteorite Iron enrichment is probably due to a higher iron

content of dark inclusions combined with iron hydroxideaccumulation from altered iron metal preferentially enrichedin the fine-grained fraction As evidenced from total irondata of ethanolamine thioglycollatendashleached samples(Table 3) about 70 of iron is easily leached and thuspresent in oxide or metallic form The silicate fractioncontains 61 to 67 wt iron which is consistent withmineral analyses by electron microprobe (Table 1) Rareearth elements (REE) are present at typical chondriticconcentrations (Anders and Grevesse 1989) with nosignificant evidence of fractionation Repeat analyses ondifferent subsamples indicate an organic carbon content inthe bulk meteorite of 029 plusmn 003 which is lower than inRenazzo Al Rais Elephant Moraine 87770 and Yamato-790112 but is similar to CRs from the Sahara (Bischoff et al1993) Assuming that most of the organic carbon isconcentrated in fine-grained dark inclusions that representlt10 of the rock a concentration of several wt carbon isrequired in these inclusions The mean total H2O content ofShiintr 033 is 607 (Table 3) which is similar to Renazzo(567 wt) and Al Rais (849 wt) (Weisberg et al 1993)Bulk chemical analyses are therefore consistent with the CRclassification of Shiintr 033 (see the Petrology section) Anunknown fraction of H2O in the fines (Table 3) is likely dueto terrestrial weathering (mainly in iron hydroxides)Furthermore the effects of terrestrial weathering are seen inthe elevated concentrations of Sr and Ba (Table 2)

Table 1 Representative microprobe analyses of the Shiintr 033 silicatesMineral Olivine Pyroxene

SiO2 (wt) 4227 4213 4155 5635 5642 5763TiO2 bd bd bd 016 011 010Al2O3 002 011 001 294 094 082Cr2O3 059 089 074 076 089 081FeO 260 241 682 409 458 345MnO 026 024 099 048 047 014NiO 004 005 bd 004 022 020MgO 5470 5490 5060 3351 3564 3704CaO 019 021 026 168 062 055Na2O bd bd bd 016 bd 004K2O bd bd bd bd bd bd

Total 10068 10094 10115 10019 10012 10098

Si (afu) 0999 0993 1000 1935 1937 1948Ti ndash ndash ndash 0004 0003 0002Al 0001 0003 0004 0119 0039 0039Cr 0011 0017 0014 0021 0024 0022Fe 0051 0047 0138 0118 0132 0098Mn 0005 0005 0020 0014 0014 0018Ni 0001 0001 ndash 0001 0006 0006Mg 1927 1928 1816 1715 1824 1791Ca 0005 0005 0007 0062 0023 0020Na ndash ndash ndash 0011 ndash 0002K ndash ndash ndash ndash ndash ndash

FaFs 0026 0024 0069 0062 0038 0025WoOr 0034 0012 0010afu = atoms per formula unitbd = below detection

1586 Z Martins et al

Table 2 Chemical composition of the CR-type carbonaceous chondrite Shiintr 033 (in two bulk samples and in fines) as measured by ICP-OES (major elements reported in wt) and ICP-MS (trace elements reported in ppm) For comparison literature CR-type carbonaceous chondrite bulk data are shown

Shiintr 033Elements Bulk Bulk Finesa Renazzob Al Raisb Average CRc

Si (wt) 1579 1567 1553 1581 1414Ti 006 006 006 011 005Al 121 117 108 125 104 118Fe 2147 2166 2367 2493 2378 2358Mn 016 016 016 018 018 017Mg 1386 1382 1210 1433 1278 1321Ca 155 151 150 127 143 129Na 015 015 018 041 046 033K lt0008 002 lt0008 003 003 003P 008 008 009 012 012LOId 646 622 761 717 1117

V (ppm) 81 71 70 78 70 72Cr 3970 3430 3410 3740 3250 3558Co 627 548 629 680 616 650Ni gt10000 gt10000 gt10000 13600 12600 13591Cu 96 78 108 80Zn 79 66 88 94 162 106Ga 485 437 555 52 680 54Ge 926 761 1084As lt5 lt5 lt5 293 147 16Rb 146 159 176Sr 148 129 162Y 269 225 223Zr 1133 773 728Nb 075 059 059Mo lt2 lt2 lt2Ag lt05 lt05 lt05In lt01 lt01 lt01Sn 187 131 163Sb lt02 lt02 lt02 0072 0098 008Cs lt01 011 011Ba 974 657 1125La 043 038 0319 03 031Ce 118 104 089Pr 019Nd 081 05Sm 024 025 020 02 0186 0212Eu 009 008 009 0079 0074 0081Gd 036 037 026Tb 011 010 005 005Dy 068 066 034 032Ho 008 008 007 01Er 024 022 021Tm 004 004 004Yb 023 023 023 0223 0211 0227Lu 003 003 003 0033 003 0033Hf 020 019 016 018Ta 004 002 003 0045Tl lt005 006 lt005Pb lt5 lt5 lt5Bi lt01 lt01 lt01Th 011 008 025U 004 004 008

aSame fraction as used for amino acid analysisbWeisberg et al (1993) Kallemeyn and Wasson (1982)cFrom Bischoff et al (1993)dLoss on ignition

The Shiintr 033 CR chondrite 1587

Amino Acid Composition and Terrestrial Contamination

We have analyzed the amino acid composition of thedesert meteorite CR Shiintr 033 Figure 3 shows a typicalHPLC-FD chromatogram of the acid hydrolyzed hot-waterextracts of the Shiintr 033 Orgueil and Murchison meteoritesas well as a serpentine blank The corresponding amino acidabundances are displayed in Table 4 The most abundantamino acids present in the Shiintr 033 meteorite extract includeL-alanine (738 ppb) L-glutamic acid (687 ppb) glycine(548 ppb) and L-aspartic acid (315 ppb) The abundances ofamino acids in the Shiintr 033 meteorite were independentlyverified by LC-ToF-MS Figure 4 displays a typicalHPLC-FD chromatogram of the Shiintr 033 Shiintr 031 andShiintr 035 meteorites as well as soil sample 78 and aserpentine blank Figure 5 displays both HPLC-FD andToF-MS chromatograms of the Shiintr 033 meteorite acidhydrolyzed hot-water extract All the corresponding aminoacid abundances are shown in Table 5 In accordance with theHPLC-FD data the most abundant amino acids in Shiintr 033determined by LC-ToF-MS are L-glutamic acid (489 ppb)glycine (417 ppb) L-alanine (330 ppb) and L-aspartic acid(189 ppb) A comparison of the Shiintr 033 amino acid contentdetermined by HPLC-FD (Table 4) and by LC-ToF-MS(Table 5) shows that the abundances generally agree withinthe experiment uncertainties However for L-glutamic acidβ-alanine and L-alanine the abundances measured byLC-ToF-MS are lower than by HPLC-FD The differencemay be explained due to the fact that amino acid identificationby HPLC-FD is based only on retention time comparisonwhile identification by LC-ToF-MS is also based on the exactmolecular mass of the eluting compounds Therefore itcannot be excluded that there could be a small fraction of co-eluting compounds contributing to the fluorescence signalintensity in HPLC-FD analyses In any case this will notchange the overall amino acid distribution in the Shiintr 033meteorite Amino acid distribution provides important clues

about the degree of terrestrial contamination and therefore thedegree of weathering suffered by the meteorite There arethree ways to evaluate the source of amino acids present incarbonaceous chondrites (see Botta and Bada 2002) 1)determination of the DL enantiomeric ratios for chiral aminoacids with a racemic ratio (DL ~ 1) indicating an abioticsynthetic origin 2) detection of amino acids in the meteoriteextract that are unusual in the terrestrial environmentincluding α-aminoisobutyric acid (α-AIB) and isovaline and3) measurement of compound-specific stable isotope ratios ofhydrogen carbon andor nitrogen In the present study theabundance of amino acids extracted from the available100 mg sample of Shiintr 033 is below the detection limit ofcurrent state-of-the-art gas chromatography isotope ratiomass spectrometers preventing the use of this method Withregard to (1) our amino acid data show that L-amino acids aresignificantly more abundant than D-amino acids in Shiintr 033(Tables 4 and 5) clearly indicating the presence of terrestrialcontamination in these samples Additionally we calculatedthe amino acid enantiomeric ratios (Table 6) in the Shiintr 033for four protein amino acids (aspartic acid glutamic acidalanine and valine) The DL ratio values obtained byHPLC-FD and LC-ToF-MS agree with each other within theexperimental error All values were found to be smaller than04 which is an indication of a high terrestrial contaminationlevel The only exception is the DL alanine ratio of 083 plusmn015 obtained by LC-ToF-MS and therefore we cannotexclude the presence of extraterrestrial components in thismeteorite The DL alanine ratios in the soil samples (Tables 5

Table 3 Percentage of iron and volatiles in different subsamples of the CR type carbonaceous chondrite Shiintr 033 (bulk samples and fines) as measured by ICP-OES and by combustioninfrared detection

Sample C total CO2 C organic H2Ominus H2O+ Fe total

Bulk 031 020 025 153 456 2147Bulk 031 lt001 030 160 446 2166Bulk 032 lt001 032 129 488 2102Bulk 030 lt001 030 140 452 2172Mean bulk

031 lt001 029 146 461 2147

Bulk ETG-leacheda 669Bulk ETG-leacheda 609

Finesb 034 lt001 034 na na 2367aEthanolamine thioglycollate leach it removes iron hydroxidesbFraction used for amino acid analysis

na = not analyzed

Fig 3 The 0 to 40 min region (no peaks were observed outside thisregion) of the HPLC-FD chromatograms OPANAC derivatizationof amino acids in the 6M HCl-hydrolyzed hot-water extracts from theCM2 carbonaceous chondrite Murchison the CI1 Orgueil the CRShiintr 033 and the serpentine blank The peaks were identified bycomparison of the retention time to those in the amino acid standardrun on the same day 1 = D-aspartic acid 2 = L-aspartic acid 3 =L-glutamic acid 4 = D-glutamic acid 5 = D L-serine 6 = glycine7 = β-alanine 8 = γ-amino-n-butyric acid (γ-ABA) 9 = DL-β-aminoisobutyric acid (D L-β-AIB) 10 = D-alanine 11 = L-alanine12 = D L-β-amino-n-butyric acid (D L-β-ABA) 13 =α-aminoisobutyric acid (α-AIB) 14 = D-isovaline 15 = L-isovaline16 = L-valine 17 = D-valine 18 = D-leucine 19 = L-leucine

1588 Z Martins et al

and 6) range from 029 to 045 with D-alanine probablycoming from the racemization of microbial detritus in the soilIf the alanine present in the Shiintr 033 meteorite was all due tocontamination then its DL ratio would be expected to fallwithin the same range Clearly the DL alanine ratio of 083 plusmn015 in Shiintr 033 is significantly higher and can best beexplained by an initial DL alanine ratio in the Shiintr 033meteorite of ~1 and a subsequent L-alanine contamination ofthe meteorite after its fall to Earth leading to the lower ratioobserved today in the meteorite Finally with regards to (2) asmall quantity of α-AIB was detected in Shiintr 033 both byHPLC-FD (34 plusmn 5 ppb Table 4) and LC-ToF-MS (38 plusmn 3 ppbTable 5) However no isovaline or β-amino-n-butyric acidwere detected (both at the same level as the detection limitTables 4 and 5) As a terrestrial contamination control wealso analyzed the amino acid content of two L6 chondrites(Shiintr 031 and Shiintr 035) collected in the same area as theShiintr 033 meteorite (Fig 1) Those meteorites are notexpected to contain any indigenous amino acid as they were

heated to gt800 degC in the parent body (Slater-Reynolds andMcSween 2005 and references therein) and therefore allamino acids observed will be due to terrestrial contaminationfrom the meteorite fall site Table 5 shows the amino acidabundances in the acid hydrolyzed hot-water extracts of Shiintr

Table 4 Summary of the average total amino acid abundances (in ppb) in the 6M HCl acid hydrolyzed hot-water extracts of the CM2 carbonaceous chondrite Murchison CI1 carbonaceous chondrite Orgueil and CR-type carbonaceous chondrite Shiintr 033 as measured by HPLC-FDa

Amino acidMurchison

CM2 Orgueil

CI1Shiintr 033

CR

D-aspartic acid 98 plusmn 5 83 plusmn 9 86 plusmn 1L-aspartic acid 182 plusmn 10 101 plusmn 22 315 plusmn 32D-glutamic acid 292 plusmn 20 45 plusmn 8 164 plusmn 15L-glutamic acid 479 plusmn 34 111 plusmn 19 687 plusmn 40DL-serineb 271 plusmn 63 386 plusmn 100 266 plusmn 97 Glycine 1429 plusmn 66 1040 plusmn 191 548 plusmn 123β-alanine 1007 plusmn 73 2784 plusmn 212 173 plusmn 7γ-ABA 647 plusmn 76 410 plusmn 40 42 plusmn 3D-alanine 617 plusmn 21 220 plusmn 40 290 plusmn 11L-alanine 708 plusmn 96 286 plusmn 42 738 plusmn 53DL-β-ABAc 529 plusmn 11 399 plusmn 17 lt10 plusmn 2d

DL-β-AIBc 353 plusmn 19 218 plusmn 20 lt2 plusmn 1d

α-AIB 1923 plusmn 275 73 plusmn 23 34 plusmn 5D-isovaline 2493 plusmn 513 52 plusmn 33 lt6 plusmn 2d

L-isovaline 2297 plusmn 316 74 plusmn 27 lt6 plusmn 1d

D-valine 395 plusmn 42 80 plusmn 4 20 plusmn 16L-valine 737 plusmn 205 346 plusmn 61 209 plusmn 49D-leucine 110 plusmn 30 17 plusmn 5 lt15 plusmn 5d

L-leucine 104 plusmn 10 72 plusmn 31 199 plusmn 25

Total 14700 6800 3800aQuantification of the amino acids included background level correction using

a serpentine blank The associated errors are based on the standard deviationof the average value between three and four separate measurements (N) witha standard error δx = σx times Nminus12

bEnantiomers could not be separated under the chromatographic conditionscOptically pure standard not available for enantiomeric identificationdThese concentrations were very similar to blank levels and therefore were

considered to be maximum values

Fig 5 The 0 to 30 min region of the HPLC-FD and ToF-MSchromatograms of the Shiintr 033 meteorite acid-hydrolyzed waterextract The peaks were identified by comparison of the retentiontime and exact molecular mass to those in the amino acid standardrun on the same day 1 = D-aspartic acid 2 = L-aspartic acid 3 =L-glutamic acid 4 = D-glutamic acid 5 = D-serine 6 = L-serine 7= glycine 8 = β-alanine 9 = D-alanine 10 = γ-amino-n-butyric acid(γ-ABA) 11 = L-alanine 12 = D-β-amino-n-butyric acid (D-β-ABA) 13 = α+β-aminoisobutyric acid (AIB) 14 = L-β-amino-n-butyric acid (L-β-ABA) 15 = L-valine 16 = ε-amino-n-caproic acid(EACA) Aspartic acid (peaks 1ndash2) could not be identified by exactmass due to poor ionization of this compound during the analysis

Fig 4 The 0 to 30 min region of the HPLC-FD chromatograms fromthe NASA Goddard analyzes OPANAC derivatization of aminoacids in the 6M HCl-hydrolyzed hot-water extracts from the Shiintr033 Shiintr 031 and Shiintr 035 meteorites soil sample (78) andserpentine blank The peaks were identified by comparison of theretention time and exact molecular mass to those in the amino acidstandard run on the same day 1 = D-aspartic acid 2 = L-asparticacid 3 = L-glutamic acid 4 = D-glutamic acid 5 = D-serine 6 =L-serine 7 = glycine 8 = β-alanine 9 = D-alanine 10 = γ-amino-n-butyric acid (γ-ABA) 11 = L-alanine 12 = D-β-amino-n-butyricacid (D-β-ABA) 13 = α+β-aminoisobutyric acid (AIB) 14 = L-β-amino-n-butyric acid (L-β-ABA) 15 = L-valine 16 = ε-amino-n-caproic acid (EACA)

The Shiintr 033 CR chondrite 1589

031 and Shiintr 035 meteorites measured by LC-ToF-MS Inthe case of Shiintr 031 glycine and glutamic acid are the mostabundant amino acids with concentrations of 24 and 6 ppbrespectively All other amino acids are present at even lowerabundance or are below the limit of detection In the case ofthe Shiintr 035 meteorite the degree of terrestrialcontamination is higher than for Shiintr 031 containingaspartic acid (398 ppb for the L-enantiomer and 126 ppb forthe D-enantiomer) glutamic acid (156 ppb for theL-enantiomer and 50 ppb for the D-enantiomer) alanine(49 ppb for the L-enantiomer and 28 ppb for theD-enantiomer) and glycine (41 ppb) as the most abundantamino acids All these amino acids are typical components ofbacteria (eg Howe et al 1965) Comparison of the aminoacid content of the L6 chondrites to the amino acid content ofthe CR Shiintr 033 can help determine which amino acids maybe in part (or totally) due to terrestrial contamination Sinceglutamic acid and glycine were detected in both ordinarychondrites it can be concluded that at least a fraction of theirabundances in Shiintr 033 is due to terrestrial contamination Itis also interesting to note the very low content of ε-amino-n-caproic acid (EACA) This amino acid is a contaminantderived from nylon bags frequently used to store meteoritesamples (Glavin et al 2006) Since all the meteorites analyzedin our study were collected in aluminum foil and

polypropylene bags it is not surprising that no EACA hasbeen detected

In an attempt to understand why the amino acidcontamination is not uniform in the two ordinary chondritesstudied we have analyzed Omani desert soils from threedifferent locations (Fig 1) using LC-ToF-MS Figure 4displays a typical HPLC-FD chromatogram of the soil 78acid-hydrolyzed hot-water extract as well as a serpentineblank with the amino acid content of all three soil samplescompiled in Table 5 In contrast to previous analysis whichshowed that the chemical composition of the Omani desertsoil is uniform (Al-Kathiri et al 2005) our data show that theamino acid distribution is not uniform in these three soils Thetotal amino acid abundances measured in these samples are1040 ppb 200 ppb and 90 ppb for soils 78 82 and 89respectively Despite these quantitative differences there issome qualitative agreement as the most abundant aminoacids in all soils are the L-amino acids and glycine Non-protein amino acids (including α-AIB) are absent in the soilwhich indicates that there was no leaching of amino acidsfrom any meteorite present in the surroundings into the soilComparison of the protein amino acid enantiomeric ratios(Table 6) of Shiintr 033 to those of the soil shows agreementwithin the experimental error Furthermore the ratios aresmaller than 04 indicating that with the exception of a small

Table 5 Summary of the average total amino acid abundances (serpentine blank corrected) in the 6M HCl acid hydrolyzed hot-water extracts of the CR type carbonaceous chondrite Shiintr 033 L6 ordinary chondrites Shiintr 031 and Shiintr 035 and three soil samples collected in the Omani deserta as measured by LC-ToF-MSb

Amino acidCR chondrite L chondrites Soil samplesShiintr 033 Shiintr 031 Shiintr 035 78 82 89

D-aspartic acid 57 plusmn 5 lt5 126 plusmn 38 68 plusmn 2 20 plusmn 1 lt10 L-aspartic acid 189 plusmn 23 lt3 398 plusmn 100 232 plusmn 53 36 plusmn 1 17 plusmn 1D-glutamic acid 124 plusmn 7 6 plusmn 1 50 plusmn 11 61 plusmn 3 24 plusmn 2 14 plusmn 1L-glutamic acid 489 plusmn 34 16 plusmn 2 156 plusmn 38 271 plusmn 5 81 plusmn 1 38 plusmn 2D-serine 32 plusmn 11 lt4 lt4 18 plusmn 2 lt4 lt3L-serine 140 plusmn 34 lt4 lt4 69 plusmn 16 lt4 lt2Glycine 417 plusmn 55 24 plusmn 11 41 plusmn 13 183 plusmn 36 4 plusmn 2 7 plusmn 1β-alanine 62 plusmn 10 9 plusmn 2 8 plusmn 2 9 plusmn 3 2 plusmn 1 3 plusmn 1γ-amino-n-butyric acid (γ-ABA) 49 plusmn 23 lt2 lt2 lt2 lt2 lt2D-alanine 274 plusmn 14 lt2 28 plusmn 11 23 plusmn 7 5 plusmn 2 lt2L-alanine 330 plusmn 59 lt3 49 plusmn 12 51 plusmn 11 17 plusmn 1 2 plusmn 2D-β-amino-n-butyric acid (D-β-ABA) lt6 lt2 lt2 lt2 lt3 lt3L-β-amino-n-butyric acid (L-β-ABA) lt4 lt2 lt2 lt2 lt3 lt3α+β-aminoisobutyric acid (AIB)c 23 lt4 lt4 lt4 lt5 lt6DL-α-amino-n-butyric acid (α-ABA)c lt5 lt2 lt2 lt2 lt2 lt2D-isovaline lt3 lt3 lt3 lt2 lt2 lt2L-isovaline lt5 lt6 lt6 lt3 lt4 lt4ε-amino-n-caproic acid (EACA) lt3 lt4 lt4 lt4 lt5 lt5D-valine 8 plusmn 3 lt2 lt2 lt2 lt3 lt3L-valine 174 plusmn 19 2 plusmn 1 11 plusmn 3 53 plusmn 16 13 plusmn 2 7 plusmn 2

Total 2300 60 870 1040 200 90aSee Fig 1 for exact location of sample collectionbAll values are reported in ppb on a bulk sample basis The associated errors are based on the standard deviation of the average value between two and four

separate measurements (N) with a standard error δx = σx times Nminus12cEnantiomers could not be separated under the chromatographic conditions

1590 Z Martins et al

extraterrestrial component (see above) most of the aminoacids in the Shiintr 033 meteorite are terrestrial in originPossible reasons for the higher contamination in Shiintr 033than in the two ordinary chondrites will be discussed in theTerrestrial Ages and Their Relationship to the Extent ofTerrestrial Contamination section

Shiintr 033 Amino Acid Composition and Comparison to Other Carbonaceous Chondrites

The typical HPLC-FD chromatograms of the acid-hydrolyzed hot-water extracts of the Shiintr 033 Orgueil andMurchison meteorites and a serpentine blank are shown in

Fig 3 with the corresponding amino acid abundances shownin Table 4 The Shiintr 033 meteorite was compared to thesetwo other carbonaceous chondrites because Murchison is awell-studied sample (and therefore can be used as a referenceto confirm accurate measurements) and Orgueil is a CI1 typewhich allows the amino acid composition to be compared tothat of the alleged CI inclusion present in Shiintr 033 (Russellet al 2004) We also compared Shiintr 033 to literature data ofthe CR chondrite Renazzo (Botta et al 2002) The mostabundant amino acids in Murchison are D- and L-isovaline(with 2493 and 2297 ppb respectively) followed by α-AIB(with 1923 ppb) Glycine β-alanine and D- and L-alanine arealso present (Table 4) In the case of Orgueil the mostabundant amino acids are β-alanine (2784 ppb) and glycine(1040 ppb) with very low levels of isovaline and α-AIB(Table 4) All these values agree with analyses performedpreviously by other authors (Ehrenfreund et al 2001 Bottaet al 2002) The Renazzo amino acid content (Botta et al2002) includes γ-ABA (1092 ppb) glycine (875 ppb)L-glutamic acid (856 ppb) and DL-β-amino-n-butyric acid(534 ppb) Comparison of the absolute amino acid content ofthe CM2 Murchison the CI1 Orgueil and the CR Renazzoshows a distinct absolute amino acid distribution for Shiintr033 meteorite In fact Shiintr 033 has a lower total amino acidcontent (3800 ppb) than any of these other carbonaceouschondrites We also compared the relative amino acid content(glycine = 1) of Shiintr 033 to the relative amino acid content of

Table 6 Amino acid enantiomeric ratios in the CR carbonaceous chondrite Shiintr 033 and in the soil sample 78 collected in the Omani desert

Enantiomeric ratio (DL)a

Amino acid Shiintr 033b Shiintr 033c Soil 78b

Aspartic acid 027 plusmn 003 030 plusmn 005 029 plusmn 007Glutamic acid 024 plusmn 003 025 plusmn 002 022 plusmn 001Alanine 039 plusmn 003 083 plusmn 015 045 plusmn 017Valine 010 plusmn 008 005 plusmn 002 lt 004

aThe uncertainties are based on the absolute errors shown respectively inTable 4 and Table 5 and are obtained by standard propagation calculation

bDL ratios calculated from the concentrations reported in Table 4 measuredby HPLC-FD

cDL ratios calculated from the concentrations reported in Table 5 measuredby LC-ToF-MS Soil selected due to the higher total amino acid abundance

Table 7 Relative amino acid abundances (glycine = 1) of several carbonaceous chondritesa

AAglycineCM2Murchison

CM1Orgueil

CRShiintr 033

CRb

Renazzo

β-alanine 071 268 032 025D-alanine 043 021 053 lt004α-AIB 135 007 006 lt008γ-ABA 045 039 008 125

aRelative amino acid abundances calculated from the absolute amino acidconcentrations reported in Table 4 measured in this study by HPLC-FD forthe CM2 Murchison the CI1 Orgueil and the CR Shiintr 033 meteorites

bThe data for the Renazzo meteorite was calculated from previous analyses(Botta et al 2002) In case only upper limits of the absolute concentrationswere measured upper limits for the relative concentrations were calculated

Table 8 Oxygen isotopic composition of the Shiintr 033 meteorite (whole rock chondrules and dark clast) measured by laser fluorination

Sample Sample typeδ17O (permil)

δ18O (permil) ∆17O

B Whole rock minus059 229 minus178B Whole rock minus070 221 minus185B2 Washed whole rocka minus233 014 minus240H Chondrules minus155 120 minus217H Chondrules minus145 141 minus218D Dark clast minus459 minus122 minus396

aTreated with ethanolamine thioglycollate

Fig 6 A comparison of the relative amino acid abundances (glycine= 1) of β-alanine (dots) D-alanine (black) α-aminoisobutyric acid(white) and γ-amino-n-butyric acid (gray) in the acid-hydrolyzedhot-water extract of different carbonaceous chondrites The relativeamino acid abundances were calculated from the absolute amino acidconcentrations reported in Table 4 measured in this study by HPLC-FD for the CM2 Murchison the CI1 Orgueil and the CR Shiintr 033meteorites The data for the Renazzo meteorite was calculated fromprevious analyses (Botta et al 2002) In the case of D-alanine and α-aminoisobutyric acid present in the Renazzo meteorite only upperlimits of the absolute concentrations were measured and thereforeonly upper limits for the relative concentrations were calculated

The Shiintr 033 CR chondrite 1591

other carbonaceous chondrites (Table 7 Fig 6) If CI-typeinclusions were present in Shiintr 033 as suggested in theinitial description (Russell et al 2004) a high relativeabundance of β-alanine similar to the CI Orgueil can beexpected (Table 7 Fig 6) However as illustrated in Fig 6the relative amino acid distribution of Shiintr 033 is dissimilarto the distribution of the CM and CI meteorites analyzedShiintr 033 has relative β-alanine and α-AIB abundances (032and 006 respectively) similar to the ones in the CR chondriteRenazzo (025 and lt008 respectively) but all other relativeamino acid abundances are significantly different (Table 7)Our data suggests that the fraction of fines of Shiintr 033analyzed in our study does not correspond neither to a typicalCI type nor to the CR Renazzo which is the only CR analyzedfor amino acids so far

Oxygen and Carbon Isotopes

The oxygen isotopic composition of the whole rock andcomponents in Shiintr 033 are shown in Table 8 and plotted inFig 7 The whole rock samples (WR and washed WR) and thechondrule composite all have oxygen isotopic signaturesindistinguishable from other CR2 meteorites The oxygenisotopic composition of whole rock samples of CR2s fall alonga mixing line of slope 07 with anhydrous silicates primarily atthe 16O-rich end and hydrous matrix and dark inclusions at the16O-poor end of the mixing line (Weisberg et al 1993) Theunwashed whole rock sample (WR) plots approximatelymidway along the mixing line suggesting that the oxygenisotopic composition is a mixture of anhydrous and

phyllosilicate material from either end of the mixing lineHowever it is not clear what the influence of terrestrialweathering (grade W2) in the form of metal oxidation and ironhydroxide staining is The sample washed in ethanolaminethioglycollate which largely removed the iron hydroxides hasan oxygen isotopic composition at the 16O-rich end of the CR2mixing line where CR2s are dominated by anhydrous phasesuch as LEW 85332 a meteorite that shows no evidence ofaqueous alteration (Clayton and Mayeda 1999)

The efficiency and effects of the ethanolaminethioglycollate wash on the samples in terms of oxygenisotopic measurements has been assessed using a suite ofvariable weathered H chondrites collected in the Tenereregion of Niger (Schultz et al 1998) which is a hot desertarea with latitudes similar to Oman Unwashed samplescollected from the Tiffa and Grein areas fall along a commonmixing line between typical H chondrite values and a point onthe terrestrial fractionation line with δ18O asymp 8permil (Fig 8) Theoxygen isotopic composition of the ethanolaminethioglycollate washed samples in the case of the lightlyweathered Grein 003 is now indistinguishable from typical Hchondrite falls while the heavily weathered Tiffa 001 is nowmuch closer to that of the H chondrite falls although it wouldappear that some weathering persists The equilibrated Hchondrites used in this study contain only well-crystallizedferro-magnesian silicates and some feldspathic phases butresults show that the ethanolamine thioglycollate washmethod is extremely efficient at removing alteration phasesfrom anhydrous silicates without noticeably affecting the bulkproperties in terms of oxygen isotopic signature Shiintr 033contains abundant (see the Petrology section) indigenousphyllosilicate-rich material and therefore it is unlikely thatthe pre-atmospheric entry whole rock oxygen isotopic

Fig 7 Oxygen isotopic composition of Shiintr 033 and othercarbonaceous chondrite groups Filled symbols for Shiintr 033 wholerock sample (WR ) composite of chondrules (chondrules )whole rock sample washed in ethanolamine thioglycollate (washedWR ) hand picked phyllosilicate rich dark clast inclusion (DarkClast ) The terrestrial fractionation line (TFL) and thecarbonaceous chondrite anhydrous mineral (CCAM) line are shownfor reference CR2 CV3 and CK data from Clayton and Mayeda(1999) CO3 data from Greenwood and Franchi (2004)

Fig 8 Oxygen isotopic composition of weathered and washed Hchondrites from Tenere Niger It illustrates the efficiency of theethanolamine thioglycollate wash method at removing terrestrialweathering products from anhydrous silicates without affecting theindigenous oxygen isotopic composition

1592 Z Martins et al

composition would plot at the anhydrous end of the CR2mixing line In addition it is likely that the ethanolaminethioglycollate washing did not discriminate betweenasteroidal and terrestrial alteration products That said it isinteresting to note that the hot-desert weathering in the Teneresamples has a δ18O of asymp8permil although it should also be notedthat the δ18O of the weathering products does appear to varyas indicated by the distinct isotopic composition of theheavily weathered H5ndash6 from Adrar Madet (Fig 8)Assuming a δ18O value of asymp8permil for the Oman weatheringproducts then any mixing line between CR2 and terrestrialweathering would be unresolvable from the indigenous CR2mixing line It is not unreasonable to assume a δ18O value ofasymp8permil given that Oman local rain water has δ18O valuesbetween minus43 and +14permil VSMOW (Waber 2006) based onrain water samples collected near Haima during the meteoritesearch project in 2005 Additionally δ18O values of monsoonprecipitation given by Fleitmann et al (2004) range betweenminus03 and 10permil (VSMOW)

The oxygen isotopic composition of the phyllosilicate-rich dark inclusion (sensu Weisberg et al 1993 sample D) isnot consistent with typical CR2 matrix or dark inclusionsfound in CR2s (Fig 7) but instead falls in the range of typicalCV3 or CK carbonaceous chondrites (Clayton and Mayeda1999) and close to those of CO3s (Greenwood and Franchi2004) These results are in contrast with the reports ofSephton et al (2006a 2006b) and Watt et al (2006) whoargue against transport and incorporation of dark inclusionsinto a matrix In that regard it would be interesting to furtheranalyze the dark inclusions measured in this work

The nature of the carbon present in the phyllosilicate-richdark inclusion D was investigated by stepped combustionwith the results shown in Table 9 and Fig 9 The carboninventory is dominated by a large release (23 wt C) in therange of 550ndash650 degC which is typical of carbonates (Wrightand Pillinger 1989) The δ13C of this component isaround minus8permil much less than typical values (δ13C of 30ndash65permil)for carbonates in carbonaceous chondrites (Grady et al1988) Given that the local carbonate deposits found in thedesert regions of Oman where Shiintr 033 was collected have aδ13C value of minus531 to minus907permil (unpublished data Universityof Bern) it is likely that the carbonates in Shiintr 033 areremobilized terrestrial carbonates At lower temperatures(150ndash350 degC) there is evidence of a smaller release oforganic carbon (04 wt C) with δ13C values rangingfrom minus34 to minus19permil The majority of this carbon appears to beterrestrial contamination which typically has a δ13C value ofminus35 to minus25permil and is quite distinct from indigenous organiccarbon found in carbonaceous chondrites with δ13C values ofminus18 to minus10permil (eg Botta and Bada 2002) It may be that thesmall amount of carbon above 300 degC is largely indigenous asthe isotopic composition approaches that expected frommeteoritic macromolecule However this component is onlypresent at the level of no more than 02 wt C assumingsome overlap with the carbonate peak

Terrestrial Ages and Their Relationship to the Extent ofTerrestrial Contamination

The terrestrial age of the carbonaceous chondrite Shiintr033 and the ordinary chondrites Shiintr 031 and Shiintr 035 aresummarized in Table 10 The expected 14C saturation value

Table 9 Stepped combustion data from a phyllosilicate-rich dark inclusion D which contains 288 wt carbon

Temperature(degC)

C yield(ng)

δ13C(permil)

50 71 minus242100 211 minus318150 712 minus335200 1992 minus301250 4712 minus268300 3980 minus213350 2392 minus193400 1880 minus150450 1609 minus114500 3606 minus82550 13001 minus66600 36939 minus78650 37960 minus76700 7607 minus78800 1505 minus76900 1779 minus80

1000 806 minus1001100 205 minus1191200 185 minus1831300 203 minus2611400 410 minus205

Fig 9 Stepped combustion profile of a dark inclusion (D) showingyield (bold histogram plot) and isotopic composition (pointline plot)with increasing temperature Organics are oxidized between 200 and500 degC while carbonates generally decompose between 500 and700 degC

The Shiintr 033 CR chondrite 1593

was approximated by using the value for L chondrites(511 dpmkg) for subsamples A B and C For Shiintr 033 a14C10Be terrestrial age of 64 plusmn 02 kyr was obtained which ismuch younger than those of the two L6 chondrites Shiintr 031(150 plusmn 04 kyr) and Shiintr 035 (214 plusmn 13 kyr) The relativelylow terrestrial age of Shiintr 033 of a few thousand years isconsistent with the low degree of weathering (W2) of the ironmetal in this meteorite In that sense the first thought wouldbe that the older age of the other two ordinary chondriteswould lead to a higher degree of terrestrial contamination ofthose samples compared to Shiintr 033 However as our aminoacid analysis shows the Shiintr 033 meteorite has a highercontamination degree than Shiintr 031 and Shiintr 035 (see theAmino Acid Composition and Terrestrial Contaminationsection) Three possibilities can be invoked to explain thisThe first is the fact that the meteorites landed in differentlocations (Fig 1) exposing them to different local terrestrialenvironments (see the Amino Acid Composition section) Thesecond possibility is the difference in porosity between the CRShiintr 033 and in the ordinary chondrites as carbonaceouschondrites have on average a higher porosity (ranging from24 to 35) than L6 chondrites (ranging from 0 to 10)(Consolmagno and Britt 1998) Although Oman is a desertthere is occasional precipitation (Sanlaville 1992 Al-Kathiriet al 2005) including monsoons during which soil materialcan be percolated through the meteorites A higher porosityand therefore a higher internal surface probably increases thechanges for absorption of organic material from the soil Thethird possibility is the difference in the oxidation state of ironpresent in the meteorites studied The significantly higherabundance of metallic iron in Shiintr 033 (see the Petrology and

Chemistry sections) may serve as a nutrient for iron-oxidizingmicro-organisms that colonialize the meteorite leading tohigher amino acid contamination degree in the CR meteoriteThis colonialization is less likely in the L6 chondrites due totheir higher content of oxidized iron

CONCLUSIONS

We have performed for the first time a multidisciplinarystudy of the Shiintr 033 meteorite which was collected in theOmani desert The initial classification as a CR chondrite isconfirmed by bulk chemical analyses as well as oxygenisotopes these latter showing that Shiintr 033 falls into the CR2group Based on oxygen isotopes dark inclusions hostingorganic material are more closely related to CV3-CO3chondrites than CR2 bulk material Amino acid analysis showsno evidence for CI- or CM-like material in these inclusions

Amino acid and carbon isotopic data indicate highterrestrial contamination in Shiintr 033 Both the Shiintr 033meteorite and the Oman soil samples show that L-amino acidsand glycine were the most abundant amino acidsAdditionally Shiintr 033 DL proteic amino acid ratios aregenerally smaller than 04 and are in agreement with theDL amino acid ratios of the Omani desert soils Carbonisotope analysis of a Shiintr 033 dark inclusion revealed highcarbonate contents with a δ13C value of minus8permil (falling withinthe range of typical terrestrial carbonates of the Omanidesert) and a low organic carbon content with δ13C valuesranging from minus34 to minus19permil However the presence of a smallfraction of indigenous extraterrestrial organic compounds inShiintr 033 cannot be excluded because the extraterrestrial

Table 10 Terrestrial age of the carbonaceous chondrite Shiintr 033 the L6 ordinary chondrites Shiintr 031 and Shiintr 035 as measured by AMS

Shiintr 031 Shiintr 033 (A) Shiintr 033 (B) Shiintr 033 (C) Shiintr 035

Type L6 CR (bulk slices) CR (bulk ground) CR (bulk ground) L6Weight (g) 0390 0269 0081 0113 0154Chemical treatment Acid etch Acid etch Acid etch Acid etch Acid etchFm 05439 10189 08992 19680 00530Error 00056 00095 00063 00180 00013CO2 (cc) 059 078 057 033 017Diluted (cc) 059 078 057 033 211714C atoms 7994 times 106 2164 times 107 1352 times 107 1746 times 107 1982 times 106

14Cweight (g) 2050 times 107 8046 times 107 1668 times 108 1542 times 108 1284 times 107

Bulk 14C (dpmkg) 472 1852 3838 3549 295Error (dpmkg) 018 031 089 069 045Saturated activitya 511 511 511 511 51114C age (kyr) 197 84 24 30 236Error (kyr) 13 13 13 13 18Bulk 10Be (dpmkg) 1170 1604 1595Error (dpmkg) 023 034 02814C10Be 040 115 01814C10Be age (kyr) 150 64 214Error (kyr) 04 02 13

aWhen class is not known 14C saturated activity of L chondrites (511 dpmkg) was used

1594 Z Martins et al

amino acid α-AIB was preserved in this meteorite overthousands of years Shiintr 033 was found to have a terrestrialage of 64 plusmn 02 kyr which is consistent with the lowweathering of its metal Differences in the amino acidcontamination content between Shiintr 033 and two ordinarychondrites (Shiintr 031 and Shiintr 035) also collected in theOmani desert can be explained by differences in thecomposition of their fall sites in the porosity of thesemeteorites in the abundances of metallic iron or acombination of these effects This study supports previousobservations that meteorites collected in hot deserts suffersignificant terrestrial alteration and contamination duringtheir residence time

AcknowledgmentsndashThe authors would like to thank Dr LindaWelzenbach (Smithsonian National Museum of NaturalHistory Washington DC USA) for providing us with aMurchison meteorite sample and the Museacutee National ParisFrance for the Orgueil meteorite sample used in this studyThis research was supported by Fundaccedilatildeo para a Ciecircncia e aTecnologia (scholarship SFRHBD105182002) NWO-VI016023003 PPARC and the NASA Astrobiology Institute atthe Goddard Center for Astrobiology Field work in Omanwas supported by Swiss National Science Foundation grant200020-107681 We acknowledge M Sephton and M Caffeefor their helpful comments

Editorial HandlingmdashDr Scott Sandford

REFERENCES

Al-Kathiri A Hofmann B A Jull A J T and Gnos E 2005Weathering of meteorites from Oman Correlation of chemicaland mineralogical weathering proxies with 14C terrestrial agesand the influence of soil chemistry Meteoritics amp PlanetaryScience 401215ndash1239

Anders E and Grevesse N 1989 Abundances of the elementsMeteoritic and solar Geochimica et Cosmochimica Acta 53197ndash214

Ash R D and Pillinger C T 1995 Carbon nitrogen and hydrogenin Saharan chondrites The importance of weatheringMeteoritics 3085ndash92

Bischoff A and Geiger T 1995 Meteorites from the Sahara Findlocations shock classification degree of weathering and pairingMeteoritics 30113ndash122

Bischoff A Palme H Ash R D Clayton R N Schultz LHerpers U Stoumlffler D Grady M M Pillinger C T Spettel BWeber H Grund T Endress M and Weber D 1993 PairedRenazzo-type (CR) carbonaceous chondrites from the SaharaGeochimica et Cosmochimica Acta 571587ndash1603

Bland P A Berry F J Smith T B Skinner S J and Pillinger C T1996a The flux of meteorites to the Earth and weathering in hotdesert ordinary chondrites finds Geochimica et CosmochimicaActa 602053ndash2059

Bland P A Franchi I A Sexton A S Berry F J and Pillinger C T1996b The oxygen isotopic composition of weathered ordinarychondrites from the Nullarbor region (abstract) Meteoritics ampPlanetary Science 31A16

Bland P A Berry F J and Pillinger C T 1998a Rapid weatheringin Holbrook An iron-57 Moumlssbauer spectroscopy studyMeteoritics amp Planetary Science 33127ndash129

Bland P A Sexton A S Jull A J T Bevan A W R Berry F JThornley D M Astin T R Britt D T and Pillinger C T 1998bClimate and rock weathering A study of terrestrial age datedordinary chondritic meteorites from hot desert regionsGeochimica et Cosmochimica Acta 623169ndash3184

Botta O and Bada J L 2002 Extraterrestrial organic compounds inmeteorites Surveys in Geophysics 23411ndash467

Botta O Glavin D P Kminek G and Bada J L 2002 Relativeamino acid concentrations as a signature for parent bodyprocesses of carbonaceous chondrites Origins of Life andEvolution of Biospheres 32143ndash163

Clayton R N and Mayeda T K 1999 Oxygen isotope studies ofcarbonaceous chondrites Geochimica et Cosmochimica Acta 632089ndash2104

Consolmagno G J and Britt D T 1998 The density and porosity ofmeteorites from the Vatican collection Meteoritics amp PlanetaryScience 331231ndash1241

Cornish L and Doyle A 1984 Use of ethanolamine thioglycollate inthe conservation of pyritized fossils Palaeontology 27421ndash424

Ehrenfreund P Glavin D P Botta O Cooper G and Bada J L2001 Extraterrestrial amino acids in Orgueil and Ivuna Tracingthe parent body of CI type carbonaceous chondrites Proceedingsof the National Academy of Sciences 982138ndash2141

Fleitmann D Burns S J Neff U Mudelsee M Mangini A andMatter A 2004 Palaeoclimatic interpretation of high-resolutionoxygen isotope profiles derived from annually laminatedspeleothems from southern Oman Quaternary Science Reviews23935ndash945

Franchi I A Bland P A Jull A J T Cloudt S Berry F J andPillinger C T 1996 An assessment of the meteorite recoverypotential of SE Arabia from meteorite weathering patterns(abstract) Meteoritics amp Planetary Science 31A46ndashA47

Gillet P Barrat J A Beck P Marty B Greenwood R C FranchiI A Bohn M and Cotten J 2005 Petrology geochemistry andcosmic-ray exposure age of lherzolitic shergottite NorthwestAfrica 1950 Meteoritics amp Planetary Science 401175ndash1184

Glavin D P Dworkin J P Aubrey A Botta O Doty J H IIIMartins Z and Bada J L 2006 Amino acid analyses ofAntarctic CM2 meteorites using liquid chromatography-time offlight-mass spectrometry Meteoritics amp Planetary Science 41889ndash902

Grady M M Wright I P Swart P K and Pillinger C T 1988 Thecarbon and oxygen isotopic composition of meteoriticcarbonates Geochimica et Cosmochimica Acta 522855ndash2866

Greenwood R C and Franchi I A 2004 Alteration andmetamorphism of CO3 chondrites Evidence from oxygen andcarbon isotopes Meteoritics amp Planetary Science 391823ndash1838

Howe J M Featherston W R Stadelman W J and Banwartz G J1965 Amino acid composition of certain bacterial cell-wallproteins Applied Microbiology 13650ndash652

Jull A J T Donahue D L and Linick T W 1989 Carbon-14activities in recently fallen meteorites and Antarctic meteoritesGeochimica et Cosmochimica Acta 532095ndash2100

Jull A J T Wlotzka F Palme H and Donahue D J 1990Distribution of terrestrial age and petrologic type of meteoritesfrom western Libya Geochimica et Cosmochimica Acta 542895ndash2898

Jull A J T Donahue D J Cielaszyk E and Wlotzka F W 1993Carbon-14 terrestrial ages and weathering of 27 meteorites fromthe southern high plains and adjacent areas (USA) Meteoritics28188ndash195

Jull A J T Cloudt S and Cielaszyk E 1998 14C terrestrial ages of

The Shiintr 033 CR chondrite 1595

meteorites from Victoria Land Antarctica and the infall rate ofmeteorites In Meteorites Flux with time and impact effectsedited by McCall G J Hutchison R Grady M M andRothery D Geological Society of London Special Publication140 pp 75ndash91

Kallemeyn G W and Wasson J T 1982 The compositionalclassification of chondrites IIImdashUngrouped carbonaceouschondrites Geochimica et Cosmochimica Acta 462217ndash2228

Lee M R and Bland P A 2004 Mechanisms of weathering ofmeteorites recovered from hot and cold deserts and the formationof phyllosilicates Geochimica et Cosmochimica Acta 68893ndash916

Miller M F Franchi I A Sexton A S and Pillinger C T 1999High-precision δO17 isotope measurements of oxygen fromsilicates and other oxides Method and applications RapidCommunication in Mass Spectrometry 131211ndash1217

Pouchou J L and Pichoir F 1984 Un nouveau modegravele de calcul pourla microanalyse quantitative par spectromeacutetrie de rayons X LaRecherche Aeacuterospatiale 3167ndash192

Ramseyer K Fischer J Matter A Eberhardt P and Geiss J 1989A cathodoluminescence microscope for low-intensityluminescence Journal of Sedimentary Petrology 59619ndash622

Russell S S Folco L Grady M M Zolensky M E Jones RRighter K Zipfel J and Grossman J N 2004 The MeteoriticalBulletin No 88 Meteoritics amp Planetary Science 39A215ndashA272

Sanlaville P 1992 Changements climatiques dans la PeacuteninsuleArabique durant le Pleacuteistoceacutene supeacuterieur et lrsquoHolocegravenePaleacuteorient 1815ndash26

Schultz L Scherer P Spettel B Wlotzka F Zipfel J Schluter JMerchel S Herpers U Newton J Franchi I A Pillinger C TLeya I Neumann S Neupert U Michel R Kubik P W SynalH-A Bonani G Hajdas I Ivy-Ochs S and Suter M 1998 Tennew meteorites from the Tenere Desert (Niger) Classificationnoble gases cosmogenic radionuclides and terrestrial ages(abstract) Meteoritics amp Planetary Science 33A13

Sephton M A Howard L E Bland P A James R H Russell S SPrior D J and Zolensky M E 2006a Delving into Allendersquosdark secrets Astronomy amp Geophysics 47637ndash638

Sephton M A James R H and Zolensky M E 2006b The

origin of dark inclusions in Allende New evidence fromlithium isotopes Meteoritics amp Planetary Science 411039ndash1043

Slater-Reynolds V and McSween H Y Jr 2005 Peak metamorphictemperatures in type 6 ordinary chondrites An evaluation ofpyroxene and plagioclase geothermometry Meteoritics ampPlanetary Science 40745ndash754

Steele I M 1990 Mineralogy of meteorites revealed bycathodoluminescence Proceedings ACS Symposium 415Spectroscopic Characterization of Minerals and Their Surfacespp 150ndash164

Stelzner T H and Heide K 1996 The study of weathering productsof meteorites by means of evolved gas analysis Meteoritics ampPlanetary Science 31249ndash254

Stelzner T H Heide K Bischoff A Weber D Scherer PSchultz L Happel M Schroumln W Neupert U Michel RClayton R N Mayeda T K Bonani G Haidas I Ivy-Ochs Sand Suter M 1999 An interdisciplinary study of weatheringeffects in ordinary chondrites from the Acfer region AlgeriaMeteoritics amp Planetary Science 34787ndash794

Waber H N 2006 Hydrochemical characterisation of groundwaterfrom the C-Aquifer Najd area Oman Institute of GeologicalSciences University of Bern RWI Technical Report 06-04

Watt L E Bland P A Prior D J and Russell S S 2006 Fabricanalysis of Allende matrix using EBSD Meteoritics amp PlanetaryScience 41989ndash1001

Weisberg M K Prinz M Clayton R N and Mayeda T K 1993The CR (Renazzo-type) carbonaceous chondrite group and itsimplications Geochimica et Cosmochimica Acta 571567ndash1586

Wright I P and Pillinger C T 1989 Carbon isotopic analysis ofsmall samples by use of stepped-heating extraction and staticmass spectrometry Proceedings Workshop on New Frontiers inStable Isotope Research Laser Probes Ion Probes and SmallSample Analysis US Geological Survey Bulletin 1890 pp 9ndash34

Zhao M and Bada J L 1995 Determination of dialkylamino acidsand their enantiomers in geological samples by high-performance liquid chromatography after derivatization with achiral adduct of o-phthaldialdehyde Journal of ChromatographyA 69055ndash63