Icarusxxx(2012)xxx–xxx ContentslistsavailableatSciVerseScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA Janice L. Bishopa,b,⇑, Heather B. Franzc,d, Walter Goetze, David F. Blakeb, Caroline Freissinetc,d, Harald Steiningere, Fred Goesmanne, William B. Brinckerhoffc, Stephanie Gettyc, Veronica T. Pinnickc,d, Paul R. Mahaffyc, M. Darby Dyarf aCarlSaganCenter,TheSETIInstitute,MountainView,CA94043,USA bExobiologyBranch,NASA-AmesResearchCenter,MoffettField,CA94035,USA cPlanetaryEnvironmentsLaboratory,NASAGoddardSpaceFlightCenter,Greenbelt,MD20771,USA dCenterforResearchandExplorationinSpaceScience&Technology,UniversityofMaryland,Baltimore,MD21250,USA eMax-Planck-InstitutfürSonnensystemforschung,Katlenburg-LindauD-37191,Germany fDepartmentofAstronomy,MountHolyokeCollege,SouthHadley,MA01075,USA a r t i c l e i n f o a b s t r a c t Articlehistory: CoordinatedanalysesofmineralogyandchemistryofsedimentsfromtheAntarcticDryValleysillustrate Availableonlinexxxx howdataobtainedusingflight-readytechnologyofcurrentNASAandESAmissionscanbecombinedfor greaterunderstandingofthesamples.MineralogywasmeasuredbyX-raydiffraction(XRD)andvisible/ Keywords: near-infrared(VNIR)reflectancespectroscopy.Chemicalanalysesutilizedaquadrupolemassspectrom- Mars,surface eter(QMS)toperformpyrolysis-evolvedgasanalysis(EGA)andgaschromatography–massspectrometry Mineralogy (GC/MS)bothwithandwithoutderivatization,aswellaslaserdesorption–massspectrometry(LD/MS) Organicchemistry techniques.Theseanalysesaredesigned todemonstratesomeofthecapabilitiesofnear-termlanded Spectroscopy Marsmissions,toprovidegroundtruthingofVNIRreflectancedataacquiredfromorbitbytheCompact ReconnaissanceImagingSpectrometerforMars(CRISM)onMROandtoprovidedetectionlimitsforsur- face-operatedinstruments:theChemistryandMineralogy(CheMin)andSampleAnalysisatMars(SAM) instrument suites onboard Mars Science Laboratory (MSL) and the Mars Organic Molecule Analyzer (MOMA)onboardExoMars-2018.Thenewdatafromthisstudyarecomparedwithpreviousanalyses ofthesedimentsperformedwithothertechniques.Tremolitewasfoundintheoxicregionsamplesfor thefirsttimeusingtheCheMin-likeXRDinstrument.TheNIRspectralfeaturesoftremoliteareconsistent withthoseobservedinthesesamples.Althoughthetremolitebandsareweakinspectraofthesesamples, spectralfeaturesnear2.32and2.39lmcouldbedetectedbyCRISMiftremoliteispresentonthemartian surface.AllophanewasfoundtobeagoodmatchtoweakNIRfeaturesat(cid:2)1.37–1.41,1.92,and2.19lm inspectraoftheoxicregionsedimentsandisacommoncomponentofimmaturevolcanicsoils.Biogenic methanewasfoundtobeassociatedwithcalciteintheoxicregionsamplesbytheSAM/EGAinstrument and a phosphoric acid derivative was found in the anoxic region sample using the SAM/MTBSTFA technique. (cid:2)2012ElsevierInc.Allrightsreserved. 1.Background observedbycurrentorbitalspectrometers.TheObservatoirepour laMinéralogie,l’Eau,lesGlacesetl’Activité(OMEGA)onMarsEx- l The objective of this study is to investigate some well- presscollectsdatafrom0.4to5.2 mataspatialresolutionofhun- characterized samples with instrumental techniques that are (or dreds of meters and documented the first conclusive evidence of will be) available on the Mars Science Laboratory (MSL) and phyllosilicates and sulfateson the surface of Mars (Bibring et al., ExoMars-2018 science payload, and visible/near-infrared (VNIR) 2005;Gendrinetal.,2005;Pouletetal.,2005).TheCompactRecon- reflectance spectroscopy in order to support coordination of the naissance Imaging Spectrometer for Mars (CRISM) collects data l data from upcoming surface missions with the mineralogy from0.4to3.9 mat7nmspectralintervalsand18m/pixelspa- tial resolution for (cid:2)12km wide swaths (Murchie et al., 2009b). ⇑ Analyses of CRISM data have revealed multiple types of aqueous Correspondingauthor. systems across Mars (Murchie et al., 2009a). Gale crater, the E-mailaddress:[email protected](J.L.Bishop). 0019-1035/$-seefrontmatter(cid:2)2012ElsevierInc.Allrightsreserved. http://dx.doi.org/10.1016/j.icarus.2012.05.014 Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 2 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx destinationofMSL,containsbothphyllosilicatesandsulfatesthat andicegrainsevenattemperaturesmuchbelowfreezing(Ander- havebeenidentifiedfromorbit(Millikenetal.,2010).Theancient son,1981).Theabundanceofsecondaryminerals(e.g.clays,zeo- mound deposits are considered to be sedimentary (Grotzinger lites and silica) correlates with the water soluble ion et al., 2011) and may have other aqueous minerals such as concentrations and may indicate that chemical alteration of soils carbonates. isoccurringtodayin subxerous regionsoftheDryValleyswhere wateractivityispresent.AmorerecentstudyofsoilsintheBeacon l 1.1.AntarcticDryValleys Valleyobservedaclayfraction(<2 m)below3%inmostsoilswith elevatedlevelsassociatedwithhighersaltcontent(Mahaneyetal., SoilsandsedimentsfromtheAntarcticDryValleys(Fig.1)have 2009),consistentwithvaluesobservedbyGibsonetal.(1983). longbeenunderstudyaspotentialanalogsforsurfaceprocesseson A recent study of doleritic rock (e.g. mafic igneous rock with Mars(Gibsonetal.,1983;McKayetal.,1985;Whartonetal.,1989; grainsizeintermediatebetweenbasaltandgabbro)andsoilsam- Doranetal.,1998).Chemicalweatheringinthecold,aridenviron- ples in Beacon Valley (Salvatore et al., 2010) found evidence of mentoftheDryValleysoccursataslowerratecomparedtoother alterationrinds on rocksurfaces. Elevated alteration levelson N- locationsonEarth,butstillresultsincomplexchemicalweathering facingslopesanddecreasedalterationonS-facingslopesareattrib- and may mimic some past martian environments (Gibson et al., uted to wind scour removal of rinds on S-facing slopes. Another 1983). Three separate zones are described in this extremely dry possibilityisthatmorewateractivityispresentonN-facingslopes, environment: subxerous environments that can support liquid promoting more alteration. Salvatore et al. (2010) found spectral water down to (cid:2)1m, xerous soils that can support liquid water featuresnear1.4,1.9and2.2lminadoleriticsoilthatareconsis- downto(cid:2)50–100cm,andultraxerousregionsthatcannotsupport tentwiththepresenceofAl-phyllosilicates.Theyalsoobservedan l liquidwaterinthesoil(CampbellandClaridge,1987;Gooseffetal., increaseinspectralbrightnessacrossthe0.5–2.5 mregionforal- 2002;Bleckeretal.,2006;Tampparietal.,2012).Xerouszonesare teredsamplescomparedtolessalteredones. themostwidespreadintheDryValleysandoccurininlandregions AnotherinterestingfeatureoftheDryValleysregionisthepres- (CampbellandClaridge,1987;Tampparietal.,2012). enceofice-coveredlakesthatprovideuniquestudyenvironments Geochemical analyses performed on soil samples from a 1m forlifeinextremeaqueoushabitats(McKayetal.,1985;Wharton deeppit inasubxerousregionat WrightValleynearLakeVanda etal.,1989;Doranetal.,1998;Fairénetal.,2010).Organismsexist foundthepermanentlyfrozenzoneatadepthof(cid:2)40cm(Gibson in microbial mats in the lake bottom sediments below both oxic et al., 1983), consistent with other subxerous regions in the Dry and anoxic regions of several perennially ice-covered lakes. Lake Valleys (Campbell and Claridge, 1987; Marchant and Head, Hoare in the Taylor Valley (Fig. 1) features an oxygen-rich (oxic) 2007).TheGibsonetal.(1983)studynotedhighersaltconcentra- zone above (cid:2)27m lake depth and an oxygen-poor (anoxic) zone tions(cid:2)2–4cmbelowthesoilsurfacethanatdepth.Thisisattrib- below(cid:2)27m(Whartonetal.,1987,1993;Andersenetal.,1998). uted to migration of brines with increasing salt precipitation LakeHoarehasreceivedabundantattentionduetothe3–5mthick upward through the soil column (Wentworth et al., 2005). Thin year-roundicecoverandalgalmatsgrowinginbothoxicandan- filmsofliquidwaterarepresentalongtheboundariesofmineral oxic regions of the lake bottom (e.g., Nedell et al., 1987; Squyres etal.,1991;Doranetal.,1994,2002;Spauldingetal.,1997). ThewatertemperatureinLakeHoarevariesfrom0.0to0.8(cid:3)C (SpigelandPriscu,1998),whilethemeanannualairtemperature above the ice is typically (cid:3)18(cid:3)C (Doran et al., 2002b). The pH of Lake Hoare was measured at 7.1 in anoxic regions at 27 and 29m depth and increased gradually upward through the oxic watersto8.8atadepthof3m(Greenetal.,1988).Caprecipitation as calcite is a dominant process in the oxic regions of the lake (Green et al., 1988; Neumann et al., 2001). Hawes and Schwarz (1999)foundthatthisprocessoccurstoagreaterextentat13m or shallower depth. Benthic and planktonic microflora thrive in the Lake Hoare ecosystem despite the low solar radiation flux, near-freezing temperatures, and highly oxygenated environment (Whartonetal.,1983,1987).CalculationsoftheO ,N andArgases 2 2 inthelakewaterandicelayercoveringthelakeshowthat11%of theO inputtoLakeHoareisduetophotosyntheticactivityinthe 2 lakeandthat40–70%ofthisphotosyntheticO isremovedthrough 2 the gas bubbles rising upward through the ice layer (Craig et al., 1992).Theprimarymeansofdepositionoflakebottomsediment in Lake Hoare is transport through the surface ice (Nedell et al., 1987;Squyresetal.,1991). Coordinatedreflectancespectroscopyandgeochemicalanalyses oflakebottomsedimentsfromtheDryValleyshaveenablediden- tificationofmineralsformedinthisenvironmentandcharacteriza- tionofmicrobialactivity(Bishopetal.,1996,2001).Thesestudies analyzed numerous sediments retrieved from oxic and anoxic zones in Lake Hoare. Calcite and organic matter were abundant inoxicregionlakebottomsediments(Bishopetal.,1996).Spectro- scopic parameters were developed to discriminate the organic C and calcite in these sediments, as the features for these groups Fig.1. MapoftheAntarcticDryValleys(a,studylocation)indicatingthelocationof l both occur in the 3.3–3.5 m spectral region. The mineralogy of theTaylorValley(b)andLakeHoare(c).Sedimentcoreswerecollectedfromdive the Lake Hoare sediments is dominated by quartz, feldspar, and holes(DH)2and4.Imagecredits:USGeologicSurvey,GeoEye,DigitalGlobeand Google. Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx 3 pyroxene(Bishopetal.,1996),consistentwiththerocksandsoils theflightunittounnecessarycontaminationordepletingitscon- fromtheDryValleysregion(CampbellandClaridge,1987). sumable resources (Mahaffy et al., 2012). The highest fidelity Reflectance and Mössbauer spectroscopy were coordinated in QMS test stand, known as the SAM breadboard, utilizes a mass order to characterize the Fe-bearing mineralogy in more detail spectrometernearlyidenticaltothatoftheSAMflightmodel,con- (Bishop et al., 2001). This enabled measurement of the relative trolled by a high fidelity RF electronics circuit and CPU that are abundancesofFe2+silicatessuchaspyroxenewithFe3+alteration bothflight unitprototypes.GCbreadboardsinclude severalcom- productssuchasclaysandoxides.Modelingofthe77KMössbauer mercial instruments that utilize columns identical or similar to spectraenabledidentificationoftwoformsofpyroxenepluspyrite those on the SAM flight model, with injection traps of the SAM usingpyroxeneparametersdefinedbyMcCammon(1995).Isoto- design. pic signatures showed that this pyrite was formed biogenically In the case of very fragile (easily degradable by pyrolysis) or fromsulfate(Bishopetal.,2001).VariationsintheCandNisotope refractory molecules, which cannot be analyzed by heating, a patternsintheanoxicsedimentsareconsistentwithactivebiolog- spaceflight-compatible chemical derivatization reaction will also ical cycling and changes in nutrient balances over time, whereas be performed (Rosenbauer et al., 1999). For example,it has been theCandNisotopepatternsintheoxicsedimentsindicatedrela- shown(GlavinandBada,1998)thataminoacidsrequirechemical tivelystableandunchangingconditions(Bishopetal.,2001).The extractionfromthesolidmineralmatrixpriortopyrolysisheating Bishopetal.(2003)studyinvolvedRamanandreflectancespectra to avoid such decomposition. One of the derivatization solvents of coarse sediment grains and additional isotopic measurements. used in SAM, MTBSTFA, can transform less labile polar organic The abundance of pyrite, chlorophyll-like spectral absorptions, compounds,suchasaminoacidsandcarboxylicacids,intovolatile andorganicCwereobservedtocorrelatewellwiththeSisotope tert-butyldimethylsilyl(tBDMS)derivativesthatcanbeseparated compositions in anoxic sediments, and microbial activity was and identifiedby GC/MS. Thisvaluable capability willalso be in- foundtobemuchhigherintheanoxicsedimentsthanintheoxic cluded on the ExoMars MOMA instrument. In addition to the sediments. Raman analyses of sediment grains showed the pres- MTBSTFA derivatization, a single-step extraction and chemical ence of chalcedony together with quartz in some sediments derivatization protocol has been developed for MOMA using the (Edwards et al., 2004). Raman analyses of feldspar grains in that dimethylformamide-dimethylacetal(DMF-DMA)derivatizationre- study found spectra consistent with a range of compositions agent. This technique allows derivatization with conservation of including sanidine, oligoclase, albite, and labradorite, and found enantiomericcentersofthemolecules,enablingthechiralanalysis pyroxenegrainscorrespondingtoorthopyroxeneandclinopyrox- of a wide range of exobiology-relevant refractory organic mole- ene.Selectedmagneticgrainswerefoundtocontaintitanomagne- cules(Freissinetetal.,2010).DMF-DMAderivatizationisalsoin- tite(Bishopetal.,2003;Edwardsetal.,2004). cluded on the COSAC experiment onboard the Rosetta lander, expected to arrive at comet 67P/Churyumov–Gerasimenko in 1.2.MSL–CheMin 2014(Goesmannetal.,2007). CheMinisacombinationX-raydiffraction(XRD)andX-rayfluo- 1.4.MSL–ChemCamLIBS rescence(XRF)instrumentonMSLthatwillprovidemineralogical information about martian soils and rock powders (Blake et al., The Chemistry and Camera (ChemCam) Laser-Induced Break- 2012).CheMinoperatesacrossanangularrangeof5to50(cid:3)2hwith down Spectroscopy (LIBS) instrument on MSL will measure ele- <0.35(cid:3)2hresolutionandwilltypicallyacquiredataoveranintegra- mentalabundancesofrocksatadistanceupto(cid:2)7musinglaser tion time of 10h. The XRD component is equipped with internal pulsesof(cid:2)14mJ(WiensandMaurice,2011).LIBSmeasuresmany chemical and mineralogical standards and 27 reusable sample elementssimultaneouslyandcanremovesurfacecoatingsthrough cells. Techniques for accurate mineralogical identifications and continuedlaserpulsesononesite.LIBSinstrumentshavethecapa- quantitativephaseabundancesforthemartiansampleshavebeen bility to quantify the abundance of important elements in sedi- establishedusinglabandfieldtests.CheMinisdesignedtoachieve ments, such as H (Cremers et al., 2012), C (Martin et al., 2003, arelativeaccuracyof15%andarelativeprecisionof10%. 2010), and S (Dyar et al., 2011) as well as most elements on the periodic chart up to Pb (Clegg et al., 2009; Tucker et al., 2010). 1.3.MSL–SAM Moreover, LIBS has the capability of fingerprinting organic mole- cules(Bricklemyeretal.,2011;Lasherasetal.,2011). TheSampleAnalysisatMars(SAM)instrumentsuite,thelargest sciencepayloadontheMarsScienceLaboratory(MSL)‘‘Curiosity’’ 1.5.ExoMars-2018–MOMA rover,willperformchemicalandisotopicanalysisofvolatilecom- poundsfromatmosphericandsolidsamplestoaddressquestions TheMarsOrganicMoleculeAnalyzer(MOMA,Goetzetal.,2011) pertaining to habitability and geochemical processes on Mars willbepartofthePasteurpayloadonboardtheExoMars-2018ro- (Mahaffy et al., 2012). The SAM analytical components include a verandincludesovensforsingleuse,aGCwithfourdifferentcol- quadrupole mass spectrometer (QMS), two pyrolysis ovens that umn types, a pulsed ultraviolet (UV) laser for solid sample canbeusedtoheateachof74samplecups,sixgaschromatograph desorptionandionization,andamassspectrometer(MS,designed (GC) columns, and a tunable laser spectrometer (TLS). Volatiles as 2D ion trap). MOMA has two fundamentally different opera- maybeintroducedintotheQMSandTLSeitherdirectlyfromthe tional modes: (a) pyrolysis-GC/MS and (b) Laser Desorption and atmosphere or by heating solid samples acquired at the martian Ionization (LDI). The ExoMars-2018 rover will be able to collect surfaceinthepyrolysisovens.Gasesevolvedfromsamplesheated subsurfacesamplesfrommultipledepths(upto2mbelowthesur- in the ovens may be conducted directly to the QMS or passed face).Usingmode(a)agivensubsurfacesamplewillbeheatedina throughoneoftheGCcolumnsfirst.Ninepyrolysiscupsonboard MOMAovenupto(cid:2)1000(cid:3)Candthereleasedvolatileswillbeana- SAM are devoted to ‘‘wet chemistry,’’ in which a derivatization lyzed by the MS only (Evolved Gas Analysis) or by GC/MS. This agent is added to the solid sample before heating to produce a modeissimilartoproceduresusedforSAM,despitesignificantdif- chemicaltransformationoforganiccompoundsinthesamplebe- ferencesindesignandhardware.Usingmode(b)thesample—un- foreanalysis. der ambient Mars conditions—will be interrogated by UV laser Severallaboratoryinstrumentteststandshavebeendeveloped pulses whereby molecular (organic and/or inorganic) fragments toallowmodelingofvariousSAMsubsystemswithoutsubjecting are vaporized and transported via an ion guide into the Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 4 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx low-pressurezoneoftheMS.Inaddition,mode(b)willreturndata per,anoxicregionofthelakeatdivehole4(DH4).SampleH3was with high spatial resolution ((cid:2)400lm, which is the anticipated thesectionofthesedimentcorefrom7to13cmdeep.Locationsof diameterofthelaserbeamatthesample)andmightrevealthedis- thediveholesareshowninFig.1c.Selectedelementalabundances tributionoforganicsamongdifferenttypesof(sand-sized)grains. fromBishopetal.(2001)forthesamplesstudiedhereareshownin Currently flight-like MOMA subsystems exist, but no overall Table 1. Similarly, the isotope patterns and carbon abundances breadboard is currently available. Therefore commercial LDI and measuredpreviously(Bishopetal.,2003)aregiveninTable2for pyrolysis-GC/MSsetupshavebeenusedtoexplorethesynergybe- comparisonwiththecurrentresults. tweenbothMOMAprocedures. 2.2.X-raydiffraction 1.6.ExoMars-2018–Raman X-raydiffraction(XRD)measurements wereperformedonthe particulate Antarctic sediments in the lab using a CheMin-like The Raman instrument planned for ExoMars (Tarcea et al., instrument.Datawerecollectedfrom5to54(cid:3)2handcomparedto 2008; Rull et al., 2011) will identify minerals and organic com- known patterns of laboratory standards. Quantitative analyses of pounds. The Raman Laser Spectrometer (RLS) employs an excita- tional wavelength of 532nm for surface spots (cid:2)50lm across the data were performed using the Rietveld refinement method (Bish and Post, 1993). Crystalline minerals present above 1wt.% (Rull et al., 2011). Raman is useful for mineral identification and cangenerallybeidentifiedtowithin±5%accuracybasedonprevious quantification of relative abundances (e.g. Haskin et al., 1997; analyses(e.g.BishandPost,1993;Hillier,2000;Oladipoetal.,2006). Sharmaetal.,2003,2011;Rulletal.,2004)andhasbeensuccess- fullyappliedtostudiesofsedimentsfromAntarctica(e.g.Edwards 2.3.Reflectancespectroscopy et al., 1997, 2004; Wynn-Williams and Edwards, 2000). Raman spectroscopy can also determine individual mineral composition, Reflectancespectraweremeasuredforparticulatesamplesina suchasthedistinctionbetweenfayaliteandforsteritewithinthe horizontalsampledishusingabi-directionalvisible/near-infrared olivine solid solution (Kolesov and Tanskaya, 1996; Mouri and (VNIR)spectrometerandaNicoletFTIRspectrometeratRELABas Enami,2008)andlowandhighCapyroxenes(e.g.Edwardsetal., inpaststudies(Bishopetal.,2001).Spectraweremeasuredrela- 2004). l tive to Halon from 0.3 to 2.6 m under ambient conditions with 5nm spectral sampling. Infrared reflectance spectra were mea- 2.Methods suredrelativetoaroughgoldsurfaceinabiconicalconfiguration with 2cm(cid:3)1 spectral sampling from 1–25lm in an environment 2.1.Samples purged of H O and CO for 10–12h. Composite, absolute reflec- 2 2 tancespectrawerepreparedbyscalingtheFTIRdatatothebidirec- l Thefrozensedimentcoreswerethawedandsamplesegments tional data near 1.2 m. Spectra over the wavelength range 0.3– l along the cores were separated by color, texture and obvious 4.4 mareincludedinthisstudy. changes in mineralogy and organic components for a previous study (Bishop et al., 2001). The samples were then ground and 2.4.Evolvedgasanalysis l drysievedto<125 mparticlesize.SamplesE2,E3andE4arelake bottomsedimentsfromanoxicregionofLakeHoarecollectedat In evolved gas analysis (EGA) experiments, powdered solid divehole2(DH2).SamplesE2,E3andE4weresedimentssectioned sampleswereheatedinaquartzcupinsideoneofSAM’spyrolysis from0.5to3,3to5and5to16cmdeep,respectively.Notethat ovens,andtheresultinggasesweresampleddirectlybytheQMS sampleE3wasnotoriginallyplannedforthisstudy,butwasadded without passing through a GC column. This is the simplest type fortheSAMGC/MSexperimentsonlyinordertoprovideadditional ofexperimentthatSAMwillperformwithsolidsamples,yielding informationabouttheorganiccompoundsintheoxicregionsedi- clues pertaining to mineralogy and the presence of organics. The mentsasithasextremelyhighabundancesofcalciteandorganics experimentsdescribedherewereperformedwiththeSAMbread- (Tables1and2).SampleH3isalakebottomsedimentfromadee- board,usingthesametemperatureprofile,pressureandgasflow Table1 SelectedmajorelementsandLOI(inwt.%). Sample SiO2 Al2O3 Fe2O3 FeO MgO CaO P2O5 Cl F S LOI E-2 55.4 13.2 0.9 3.2 3.2 12.3 0.14 0.05 0.04 0.03 5.6 E-3 26.4 5.5 1.2 1.0 1.8 32.8 0.17 0.09 0.16 0.11 29.1 E-4 59.4 15.1 1.0 3.7 3.9 7.8 0.15 0.09 0.02 0.04 2.2 H-3 59.7 14.3 0.9 5.5 3.8 4.6 0.18 0.02 0.10 2.02 4.0 Notes:TheelementalabundancesweredeterminedbyXRFwithFe3+andFe2+separatedbyMössbaueranalyses(Bishopetal.,2001);samplesweredriedat105(cid:3)Cpriorto XRFandlossonignition(LOI)wasdeterminedat850(cid:3)C. Table2 AbundanceofcarbonateandorganicsandisotopicratiosofC,NandS. Sample Cin(wt.%) CO2(wt.%) Corg(wt.%) H2O(wt.%) d13C d15N d34SCRS d34SSS Region E-2 1.04 3.81 0.38 1.03 (cid:3)20.4 3.2 Oxiczone E-3 6.33 23.2 1.80 3.61 Oxiczone E-4 0.34 1.24 0.14 0.44 (cid:3)19.5 3.0 0.14 5.91 Oxiczone H-3 0.03 0.11 1.02 1.52 (cid:3)26.3 (cid:3)5.6 (cid:3)21.83 (cid:3)19.23 Anoxiczone Notes:Theinorganic(Cin)andorganic(Corg)carbonabundancesweredeterminedusingaLECORC-412multiphasedeterminator(Bishopetal.,2001);CandNisotope measurementswereperformedbyDumascombustiontechniquesonthebulkorganicmaterialineachsample(Bishopetal.,2001);Sisotopesweremeasuredforthechrome reducedsulfide(CRS)andacidsolublesulfate(SS)componentsusingaFinniganMAT252massspectrometer(Bishopetal.,2003). Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx 5 rateastheflightmodel.DuringanominalEGArun,thepyrolysis 10(cid:3)C/min up to 320(cid:3)C. The DSQII scanned from m/z 45 to 535, oven is heated from ambient temperature to (cid:2)1000(cid:3)C at a con- withm/z535beingtheupperlimitontheSAMinstrument. stantramprate,usually35(cid:3)C/min.Asvolatilesarereleasedfrom The derivatization was performed on another similar GC/MS the sample, they are swept through the gas manifold by helium instrument, interfaced with a CDS5100 pyroprobe using quartz (He)carriergas.Thegasmanifoldincorporatesflowrestrictorsto boatsforsampleinsertion.Eachsamplewasprocessedinthefol- obtain a nominal He pressure of (cid:2)35mbar inside the pyrolysis lowingmanner:25nmolofpyreneand40nmolof3-Fluoro-DL-va- oven. The QMS continuouslysamples the outflowfrom the oven, line were deposited as a solution in the boat, then dried. Pyrene scanning over the m/z range of interest. Different types of com- was the general standard of the experiment used to determine poundsthermallydecomposeatdifferenttemperatures,sothevar- thesuccessoftheGC/MSrun.3-Fluoro-DL-Valinewasastandard iationinQMSsignalwithtemperatureprovidesinformationonthe not expected to be present in the sediments under analysis and sample’scomposition.Integrationofsignalovertimeforparticular wasutilizedtoconfirmthesuccessofthederivatizationreaction. compoundsenablesquantitativeestimatesofchemicalandisoto- 50.7,47.1,50.6and51.8mgofsamplesE2,E3,E4andH3,respec- l picabundance. tively,werecombinedwith50 LofamixtureofN-methyl-N-(ter- tbutyldimethylsilyl)trifluoroacetamide (MTBSTFA)/dimethylform- amide(DMF)(4:1).Thepreparedsamplewasimmediatelyinserted 2.5.Gaschromatography/massspectrometry intothepyroprobeandheatedto300(cid:3)Cfor3minunderHeflowto allow for the one-pot/one-step extraction, derivatization and The GC/MS (gas chromatography/mass spectrometry) experi- transfer (Buch et al., 2009) of the organic molecules to the trap, mental setup includes four subunits: (1) the oven (stepped or aswillbeperformedonSAM.Theratioandquantitiesofchemicals rampedheatingupto(cid:2)1000(cid:3)C),(2)thecoldtrap,whereevolved arethesameasthoseplannedintheSAMderivatizationcups.The volatiles are trapped at temperatures somewhat below 0(cid:3)C, (3) samplewascollectedat50(cid:3)ConaSAM-liketrapcomposedofglass theGCunitwithasetofdifferentcolumnsforresolvingcomplex beads,TenaxTAandCarbosieve,thendesorbedat300(cid:3)Cfor2min. mixturesofevolvedvolatilesintoseparatecomponentsaccording The GC/MS runs were performed under a He carrier flow rate of totheirentrainmentbythemobilephase(usuallyHegas)andtheir 1.5mL/minona30m-longRxi-5capillarycolumnfrom50(cid:3)C(held interactionwiththestationaryphase,and(4)amassspectrometer. 2min)to220(cid:3)Cwitharampof10(cid:3)C/min,thenarampof20(cid:3)C/ The mass spectrometer for SAM is a QMS, while the mass spec- minupto320(cid:3)C.Themassdetectionrangeswerem/z45to435 trometerplannedforMOMAisa2-D(linear)iontrapthatiscur- inthisstudy. rently in the design phase. The initial heating step can be TheothersetupthatwasusedasaproxyfortheMOMAGC/MS enhancedbyreleaseofaso-calledderivatizationagentthattrans- includeda Pyrola 2000 unit connected to a Varian 3800 GC with formspotentialorganicmolecules(e.g.acids)intoamorevolatile Rtx-20 column (30m(cid:4)0.25mm(cid:4)0.15lm) and a Varian 4000 form (e.g. esters). The derivatization reagent, by reacting with ion trap MS with internal ionization. The sample was heated by thelabilehydrogenofthemoleculespresentinthesoil,improves thePyrolato900(cid:3)Cwithin15ms.Volatilesreleasedduringheat- thedetectionintwoways.Firstofall,itwillpreventfragileorgan- ingandseparatedbytheGCcolumncanbedetectedwithinamass icsfrombeingdegradedbytheheatofpyrolysis.Secondly,bycap- rangefrom35toabout500Da.Thelowerendofthatrangeisset ping the refractory and/or polar reactive groups of organic foreliminationofabundantlightmoleculessuchasnitrogen,oxy- molecules that make them challenging to detect by GC/MS, the gen,andwatervapor. derivatization process transforms them into more volatile mole- cules that are more amenable to GC/MS analysis. Both improve- 2.6.Laserdesorptionandionization ments added by the derivatization enable detection of a broader range of organic molecules than pyrolysis alone. Both SAM and Powdered samples E2, E4, and H3 were prepared for Laser MOMAwillapplythederivatizationtechnique,althoughthederiv- Desorption and Ionization (LDI) analysis by suspending 12mg of atizationagentmaynotbeidentical.Herewepresenttwodifferent as-receivedparticulatein200lLof18MXDIwater.A2lLslurry data sets acquired on Lake Hoare sediments: (a) data acquired aliquot was pipetted onto highly-polished ground stainless steel usingaflight-likeconfigurationwithprotocolssimilartothoseof multi-targetplates,thenairdriedleavinganopaquespotapprox- SAM GC/MS, and (b) data using a commercial GC/MS set up that imately4mmindiameter.Sampleplateswereloadedintothetar- is employed as a reference accompanying the MOMA hardware get source of either of two laboratory-grade laser mass development. spectrometers.Organicacidssuchasthoseusedinmatrix-assisted Pyrolysis and derivatization performed in a commercial laserdesorption/ionization(MALDI)werenotaddedtothesample CDS5100pyroprobeandacommercialThermoDSQIIGC/MSused for these experiments, so that the analysis conditions would be anapproachsimilartothatoftheSAMexperiment.Thepyrolysis analogoustothe‘‘dry’’approachusedinMOMA.Laserdesorption was performed in an organic-free quartz tube where 10.0, 10.4, iontrapmassspectrometricanalysiswascarriedoutusingaTher- 10.9and 7.5mg ofpowderedsamplesE2,E3,E4 and H3,respec- mo Scientific MALDI LTQ XL unit equipped with a nitrogen l tively,wereinserted.Thequartztubewaspackedwithglasswool (337nm)commerciallaseroperatedat20–30 Jenergyperpulse l on each side. A blank with no powder was processed under the and focused to a spot of approximately 100 m diameter. The same conditions before each sample to avoid any contamination instrument uses a linear ion trap (LIT) mass analyzer analogous from the previous experiment. The sample was pyrolyzed under to MOMA. Spectra were obtained in full scan positive ion mode Hecarriergasflowfrom250to750(cid:3)Catarateof250(cid:3)C/min,hold- uptoamolecularweightof1500Daandwithanautomaticgain ingthemaximaltemperaturefor2min.Ahydrocarbontrap(Tenax controlalgorithmoptimizingthenumberoflaserpulsesperscan TA), capturing the molecules pyrolyzed downstream, was set at tomaintainsignalsin atractablerange.Supportinglaserdesorp- 50(cid:3)C during pyrolysis. The He flow was then reversed from the tiontime-of-flight(TOF)massspectrometricanalysiswasalsocar- trap to the GC inlet while the trap was heated to 300(cid:3)C for riedoutusingaBrukerAutoflexSpeedMALDITOF/TOFequipped 4min to desorb the organics. GC/MS analysis was achieved on a withafrequency-tripledNd:YAG(355nm)commerciallaseroper- 30-mlengthcapillarycolumnRtx-5mssimilartooneoftheSAM atedatslightlyhigherpulseenergies.TheBrukerinstrumentpro- GCcolumns,usuallyusedforseparationof>C15organics.TheHe videdacross-checkoftheiontrapdata;resultsfromtheLTQXL flowratewas1.5mL/minandthetemperaturerangevariedfrom reportedhereareallconsistentwithTOFanalysis(notfurtherpre- 50 to 320(cid:3)C with a rate of 5(cid:3)C/min from 50 to 220(cid:3)C, then sentedhere)whichwasalsoconductedinpositiveionmode.The Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 6 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx Autoflex was further used to examine the structure of selected Theoxicregionsedimentspectra(E2andE4)arecomparedin compounds through isolation and tandem mass spectrometry Fig. 4 to spectra of calcite, biotite (mica, K[Mg,Fe2+] Al- 3 (MS/MS),acapabilitythatisincludedinMOMA. Si O [OH] ), tremolite and allophane that are likely present 3 10 2 based on the XRD results (Fig. 2) and previous analyses of these samples including spectra at longer wavelengths (Bishop et al., 3.Results 1996, 2001). Biotite spectra exhibit a weak OH stretching over- l l tonebandnear1.4 m,abandat2.259 mduetotheOHstretch- 3.1.X-raydiffraction ingandbendingcombinationforOHconnectedtoAlandeitherFe l or Mg and a band at 2.366 m for the OH combination band for XRDpatternsareshowninFig.2forsamplesE2,E4andH3.Riet- three Fe2+ cations (Bishop et al., 2008). Raman spectra of some veld refinements on these data indicate the presence of several grains matched well with prehnite (Edwards et al., 2004); how- minerals.TheseresultsareconsistentwithpreviousXRDanalyses ever, prehnite spectra in this region have bands at 1.48 and (Bishopetal.,2001), butgivemoreaccuratemineralabundances l 2.35 m that are not observed in the spectra. Amphibole spectra duetotheRietveldrefinements.Theoxicregionsamplesaredom- contain a quartet due to the OH stretching overtone at 1.392– inatedbyquartz,feldsparandpyroxenewithcarbonateandsome l 1.396,1.397–1.402,1.403–1.408,and1.405–1.416 mplusadou- amphibole.MineralsdeterminedforsampleE2inorderofdecreas- blet due to the OH stretching and bending combination tones at ingabundance(withapproximatechemicalformula):albite(feld- l 2.313–2.337 and 2.384–2.403 m depending on where the min- spar, NaAlSi O ), quartz (SiO ), anorthite (feldspar, 3 8 2 eral chemistry falls along the tremolite-actinolite line (Mustard, [Ca,Fe]Al Si O ),diopside(pyroxene,CaMgSi O ),enstatite(pyrox- 2 2 8 2 6 1992). The E2 and E4 spectra include features at 2.25–2.26, ene,[Mg,Fe]SiO3),calcite(carbonate,CaCO3),andtremolite(amphi- 2.30–2.31 and a shoulder near 2.37–2.39lm that are consistent bole, Ca Mg Si O [OH] ). Sample E4 contains albite, quartz, 2 5 8 22 2 withmica(e.g.biotite)andamphibole.Thesebandsshiftslightly anorthite,diopside,enstatite,tremolite,andcalcite.TheXRDresults with mineral chemistry and unique identifications cannot be fortheanoxicregionsampleH3gavealbite,quartz,anorthite,diop- madeusingthesespectraalone.Micaandamphibolespectraalso side,enstatite,andpyrite(sulfide,FeS2).Thepyritedetectedhereis containsharpOHstretchingvibrationsnear2.7–2.8lmthatcould consistentwiththedetectionofthismineralbyMössbauerspec- beconsistentwithsmallfeaturesobservedinthesedimentspec- troscopywithanappliedmagneticfield(Bishopetal.,2001).The tra,althoughtheseareobservedinthespectrumofH3aswellas variable feldspar and pyroxene compositions are consistent with E2 and E4, and the H3 spectrum does not contain other features previousRamananalysesonthesesamples(Edwardsetal.,2004). consistent withmicaor amphibole. AllophanespectraincludeanOHstretchingovertonedoubletat l l 3.2.VNIRReflectanceSpectroscopy 1.37and1.41 m,abroadwatercombinationbandnear1.92 m, l and an OH stretching and bending combination band at 2.19 m TheVNIRreflectancespectraofoxicregionsedimentsE2andE4 (Bishopetal.,2012).Theshapeofthebroadbandsnear1.93and l l exhibitbandsnear1and2 mcharacteristicofpyroxene(Fig.3). 2.20 minspectraofsampleE-2aremoreconsistentwithspectra The band centers for these two samples occur at 0.93 and 1.90– of allophane than Al-smectites that have an asymmetric water 2.0lm, which are consistent with an (cid:2)50/50wt.% mixture of bandat1.91lmandanarrowerbandnear2.2lm.However,the low-Ca and high-Capyroxeneor a pyroxenehavingintermediate bandsareweakandformixturesliketheseitisdifficulttomake composition (Cloutis and Gaffey, 1991; Sunshine and Pieters, auniquemineralassignment.BothAl-smectiteandallophaneare 1993) due to electronic excitationsin Fe-bearingsilicates (Burns, consistent with the spectral features observed for sample E-2 1993). The H3 spectrum has a weaker band near 0.93 and a hint (Figs. 3 and 4); however, allophane is a more likely component l of a band near 2 m as well that are consistent with a mix of based on the positions of the NIR bands, limited chemical alter- pyroxenes.Thepresenceoftwopyroxenesisconsistentwithpre- ationofthesamples,and thefactthatAl-smectiteswerenotob- vious Mössbauer spectroscopy analyses of these samples (Bishop served by XRD in this study or by Raman in an earlier study etal.,2001),Ramananalyses(Edwardsetal.,2004),andthecur- (Edwardsetal.,2004). rentXRDanalyses(Fig. 2).Pyritehasverylowreflectancein this regionandthusthepresenceofpyriteinH3couldberesponsible 3.3.Evolvedgasanalysis forthelowerreflectanceobservedforthissample. l Astrongbandnear2.7–3.1 mispresentinspectraofallthree To demonstrate SAM’s capability to detect organic and inor- samples and is due to H O and OH stretching vibrations in hy- ganic materials of interest from this Mars analog environment, 2 dratedcomponents(e.g.Eisenbergand Kauzmann,1969;Farmer, EGAanalyseswereperformedwiththeLakeHoaresamplesdesig- 1974; Bishop et al., 1994). Smaller features at 2.34, 2.53, 3.36, nated E2, E4, and H3 (Bishop et al., 2001). Sample masses were l 3.48, and 3.98 m are characteristic of calcite (e.g. Bishop et al., 14.6mg, 12.8mg, and 12.2mg, respectively. Fig. 5a–c illustrates l l 1996)intheoxicregionsamples.The3.41 mbandand3.51 m theEGAprofilesfromthesethreesamples.Theresultsrevealnota- shoulderareduetoaliphaticCH stretchingvibrations(e.g.Bruno ble differences in volatile content between sediments E2 and E4, 2 andSvoronos,1989;Gaffeyetal.,1993;Bishopetal.,1996).These from the shallow, oxic part of the lake, and sediment H3, from aremostprominentintheanoxicregionsamples,butnotablealso the lake’s deep, anoxic region. The largest peak for sediment E-2 inthespectrumofE2.ThespectrumoftheanoxicregionH3sam- inFig. 5aappearstobe waterreleased fromhydrousmineralsat plealsoexhibitsadoubletfeatureat0.67and0.70lm.Thisischar- temperatures of (cid:2)250–650(cid:3)C. However, the CO peak released 2 acteristic of spectral features due to chlorophyll-like pigmenting from carbonate minerals between (cid:2)500 and 750(cid:3)C is actually agents (Hoff and Amesz, 1991). Additional weak bands at 1.40, manytimeslargerthanthewaterpeak.Toenabledepictionofall 1.92, 2.20, 2.25, 2.30 are attributed to phyllosilicates (e.g. Bishop compoundsonasingleplot,theCO traceinFig.5ashowstheiso- 2 etal.,2008)and/oramphiboles(Mustard,1992)inspectraofthe topologueatm/z45,withpeakheight(cid:2)2.5(cid:4)105counts/s,instead oxic region samples. Phyllosilicates were not observed by XRD, ofthemajorpeakatm/z44,withapeakheight(cid:2)2.1(cid:4)107counts/ whichsupportsthepresenceofallophane(nanophasealuminosil- s. Minor sulfate abundance is indicated by the small SO peak 2 icate, [Al O ][SiO ] [H O] ) an X-ray amorphous material above (cid:2)800(cid:3)C. Aliphatic hydrocarbons are represented by peaks 2 3 21.3–2 2 2.5–3 (vanderGaastetal.,1985)thathasVNIRspectralpropertiessim- at m/z 27 and 15. The bulk of these compounds are released be- ilartoAl-smectites(Bishopetal.,2012). tween (cid:2)300 and 650(cid:3)C, but there is an additional m/z 15 peak Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx 7 Fig.2. XRDindicatingmineralsobservedinsamplesE2,E4andH3. coincidingwiththatofCO ,believedtoindicatemethanereleased much lower abundance of aromatic hydrocarbons, represented 2 upon thermal degradation of the carbonate mineral matrix. A bym/z78,isseenprimarilybetween(cid:2)400and600(cid:3)C. Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 8 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx Fig.3. VNIRReflectancespectraofAntarcticsedimentsamplesE2,E4andH3from 0.3 to 4.4lm showing features due to pyroxene, carbonate, phyllosilicates, hydrocarbons,andchlorophyll. Fig.5. SAMevolvedgasanalysisresultsforsamples:(a)E-2,(b)E-4,and(c)H-3. Fig.4. VNIRreflectancespectraofAntarcticsedimentsfrom1to2.65lmcompared Numbers in parentheses indicate m/z values for the traces shown. See text for withmineralspectrafrompreviousstudies:calcite(Bishopetal.,2004),biotite discussion. (Bishopetal.,2008),allophane(Bishopetal.,2011),andtremolite(USGSspectral library,http://speclab.cr.usgs.gov/,Clarketal.,2007). peakforE4above800(cid:3)Cissubstantiallylowerthanthatobserved TheEGAprofileofsedimentE4isshowninFig.5b.Thissample forE2. releasedsignificantlylesswaterthanE2,overasmallertempera- Fig. 5c shows EGA results for sediment H3, which differ sub- turerange.TheCO2peakbetween(cid:2)450and800(cid:3)Cagainisrepre- stantially from those of E2 and E4. H3 shows the highest abun- sented by m/z 45, while the major isotopologue at m/z 44 has a dances of water and organic compounds, both aliphatic and peakat(cid:2)4.6(cid:4)106counts/s.Bishopetal.(2001)measuredthecal- aromatic,ofthethreesamples,afindingthatagreeswiththewater cite abundance of E2 as 3.81wt.%and E4 as 1.24wt.%. Assuming and organic carbon abundances reported by Bishop et al. (2001) thattheEGACO2peakinbothsamplesderivessolelyfromcarbon- andincludedinTable2.Thelargestwaterreleaseoccursbetween atedecomposition, normalizationof resultsbasedontherelative (cid:2)150and450(cid:3)C,withasecond,smallerpeakcoincidingwithSO 2 masses of the two samples suggests carbonate content in E2 produced by pyrite degradation at (cid:2)450 and 600(cid:3)C. Aliphatic approximatelyfourtimeshigherthanthatinE4.Inreality,apor- hydrocarbonsevolveprimarilyfrom(cid:2)300to600(cid:3)C,withasmaller tion of the CO2 peak probably represents organic material that peak above (cid:2)700(cid:3)C. The abundance of CO2 released from this hasbeenoxidizedinthepyrolysisoven.Them/z15and27peaks sample is significantly lower than those of the previous two corresponding to aliphatic hydrocarbons in E2 are approximately samples, with the m/z 44 peak at carbonate temperatures at threetimeshigherthanthoseofE4,consistentwithagreatercon- (cid:2)8.5(cid:4)105counts/s.Thisisconsistentwiththe0.03wt.%inorganic tributionoforganicmaterialtotheCO2peakintheformersample. C found in sample H3 attributed to 0.11wt.% CO2 as carbonate Theabundanceofaromatichydrocarbonsisalsonotablylowerin (Bishopetal.,2001). E4.Bothoftheseobservationsareinagreementwiththerelative TheCO traceinFig.5cshowstwoadditionalpeaksattemper- 2 abundances of organic matter reported for these sediments by atureslowerthanthatofcarbonatedecomposition,indicatingoxi- Bishopetal.(2001).AsforE2,sampleE4alsorevealsmethanere- dationoforganiccompoundsinthepyrolysisoven.Thisfigurealso leased simultaneously with carbonate degradation. The sulfate includes the m/z 28 trace, representing primarily CO produced Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx 9 fromoxidationoforganicmaterial.Thelargem/z28peakfrom600 exampleofthis,identifiedthroughoutthechromatogramfromtol- to1000(cid:3)Cisinterpretedtoindicateincompleteoxidationofrefrac- uene (methylbenzene, C7) to docosylbenzene (C28). This could toryorganiccompoundstoCOintheabsenceofsufficientoxygen indicateeitheracomplexchemistryofbuildingblocksuptoasig- toproduceCO .Thecoincidentm/z27peakindicatesthepresence nificant amount of carbon, or degradation of a higher molecular 2 ofaliphatichydrocarbonfragmentsatthesetemperatures.Thereis weightmoleculeintosmallerfragments.Thedegradationcouldoc- noevidenceofmethanereleaseduponthermaldegradationofthe cur naturallyin the sediment or be enhanced by pyrolysisof the carbonatemineralmatrixforsampleH3,perhapsbecauseofvery sample. Other aromatics (furan ring and derivatives) or PAH-like lowcarbonateabundanceforthissample. fluoreneandderivativesarealsopresent. Theotherrepresentativegroupsoforganicmoleculespresentin 3.4.Gaschromatography/massspectrometryinaSAM-similar sampleE2arealkanesandtheircorrespondingalkenes,whichcan- configuration notbeidentifiedbelowC13(tridecane/tridecene),butcanbeeasily identified with additional CH units up to C19 (nonadecane/non- 2 3.4.1.Pyrolysis adecene). Alkane- and alkene-bearing compounds are present in Thepyrolysistechniqueutilizedinthisstudyenablesextraction the latest part of the chromatogram (longer time) but cannot be ofvolatilemoleculesfromasamplebyheatingathightemperature uniquelyidentified.Nitrogenisrevealedprimarilyasnitrilefunc- forashorttimeperiod.However,sinceextendedheatingisneeded tionalgroupsandasindoleanditsderivativesinafewcompounds. to extract more complex molecules, only low to mid-molecular Additional organic compounds are also present (as indicated by weightorganicmoleculescanbedetectedbythistechnique.(Note severalpeaks),buttheycouldnotbeidentifiedbymatchingtheir that SAM has considerable flexibility in its possible heating pro- respectivemassfragmentationpatternstotheNISTspectrallibrary files,constrainedprimarilybytheavailablepower,andthemethod duetolowerabundancesand/orbackgroundpeakinterferences. chosenforthisstudydoesnotreflectlimitationsoftheSAMinstru- Sample E4 displays the same qualitative organic content as ment.) The pyrolysis was performed from 250 to 750(cid:3)C to allow sampleE2,butinalowerabundance.Therearenoadditionalcom- more volatile molecules to be extracted without degradation at poundsinE4thatwerenotidentifiedinE2.However,thereisasig- mild temperature, and more refractory matter to be extracted at nificant quantitative difference between these two samples from highertemperatures.Thisrangeoftemperaturesisconsistentwith theGC/MSspectra.E4,whichisfromadeeperpartofthesediment the EGA results, in which aliphatic hydrocarbons were extracted layerofLakeHoare,showsatleasttwotothreetimeslowerabun- between 300 and 650(cid:3)C and aromatic hydrocarbons between dance of most organic compounds, consistent with organic con- 400and600(cid:3)C. tents measured previously (e.g. Bishop et al., 2001). In contrast, ThechromatogramofsampleE2(Fig.6)displaysalargevariety the simplest aromatic compound, benzene, is present in E4 at and great abundance of organic molecules, which presents some twotimesthelevelfoundinE2.Thismeansthattheratioofben- challengesforidentificationofeachindividualpeakduetocoelu- zene(and/orparentmoleculesdegradingtobenzeneduringpyro- tions(when multiplecompoundsexit thecolumntogether).Sev- lysis) to other organic molecules is 4- to 6-times higher in eral different aromatic and aliphatic compounds were identified sediment E4 than in E2. This higher relative abundance might by their mass fragmentation patterns (some major structures come from degradation of more complex molecules to the most showninFig.6).Thecoreofthearomaticcompoundsarebenzene stableone.Onecaninferthatthesedimentsdepositedinthislayer (1 ring), naphthalene and biphenyl (2 rings), phenylnaphthalene, areolderthantheonesatthesurface,andunderwentconditions phenanthreneandp-terphenyl(3rings)andpyrene(4rings),these that couldhave led to the partial oxidationor degradationof or- lattergroupsreferredtoaspolyaromatichydrocarbons(PAH).All ganicmolecules. ofthesekeycompoundsexceptpyrenealsoexistunderbranched SampleE3issimilartosamplesE2andE4,buthaselevatedlev- forms by adding one or more alkyl, alkene, alcohol or carbonyl elsoforganicsandcalcite(Table2).Itwasaddedtothispartofthe groups.Thereisalsoaseriesofcompoundsproducedbyrepetitive studyfordetailedanalysesoftheorganicmolecules.Themaindif- additions of functional groups to a molecule, thus increasing the ference is the presence of a high level of carboxylic acids, which massinasystematicmanner.Alkyl-benzeneisthemostrelevant werenotdetectedinsamplesE2andE4.Thefourmaincarboxylic Fig.6. Thechromatogramafterpyrolysisof10.0mgofsampleE2,fromtheoxicregionofLakeHoareshowingmassdetectionfromm/z45to535.Themainandmosteasily identifiablepeaksarerepresentedonthechromatogram,themajorityofwhicharePAHsupto4rings.Branchedbenzeneringsareparticularlypresent,aswellasaliphatic hydrocarbons.Fewnitrogen-richcompoundswereobserved. Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014 10 J.L.Bishopetal./Icarusxxx(2012)xxx–xxx acidsaredetectedbytheirmassfragment129,andareidentified Chromatograms were obtained after derivatization of 47.1mg as dodecanoic acid (C12), tetradecanoic acid (C14), hexadecanoic of sample E3 (Fig. 9, top), 51.8mg of sample H3 (Fig. 9, middle) acid(C16)andoctadecanoicacid(C18).Thisrevealsaseriesofcar- and a blank (Fig. 9, bottom). The extractionand derivatizationof boxylicacidswithprogressiveincreasesinmolecularmassequiv- organic molecules was performed as a one-pot/one-step reaction alenttotwoCH groups,whichcanberelatedtolife.Indeed,fatty by heating the mixture to 300(cid:3)C for 3min. In each sample, 2 acids,whicharebiologicalcarboxylicacidsandcanbedegradation 50nmol of standard pyrene and 40nmol of standard 3-Fluoro- productsoflipids,existonlywithanevennumberofcarboninliv- DL-Valine were used. Those were the only molecules present in l ingsystems,duetotheirformationpathway.Simplystrongdetec- the blank before addition of the derivatization reagent (10 L of l tion of fatty acids implies a biological origin of the molecules MTBSTFA/DMF 4:1 for the blank and 50 L of MTBSTFA/DMF 4:1 identifiedinthisoxicregionofLakeHoare. for the Lake Hoare samples). The organics were collected on a As demonstrated by EGA and LDI analysis,sample H3 is quite SAM-like trap (glass beads, Tenax TA and carbosieve) kept at differentfromtheEseriessamplesfromquantitativeandqualita- 50(cid:3)C, then released to the GC by heating the trap to 300(cid:3)C for tive points of view. This result is confirmed by the GC/MS data 2min. The 30-m SAM-like GC column is an Rxi-5. It was heated (Fig. 7). The main compound detected is octathiocane (S8). The from 50 (hold 2min) to 220(cid:3)C at a 10(cid:3)C/min rate, then 220 to detection of hexathiocane (S6) in a lesser amount and of sulfur 320(cid:3)Cata20(cid:3)C/minrate. incorporated into aromatic and aliphatic hydrocarbons is consis- Incomparisontopyrolysisandothertechniques,derivatization tent with the presence of pyrite in this sediment (Fig. 2, Bishop ofsamplesE2,E3andE4displaysimilarqualitativepatterns,with et al., 2001). In this sample, the chromatogram displays signifi- aromatics and aliphatics derivatized. The main challenge for the cantly more nitrogenated compounds than any of the E series, identification of the mass spectra of the well-separated peaks on and amines are detected as well. More alcohols, alkanes and al- the chromatogram is the lack of MTBSTFA-derivatized molecules kenes,andmethylalkylderivativesareobserved,andmoremole- in the NIST library, which requires a singular knowledge of the cules of higher molecular weight and complexity are identifiable derivatized compounds. The molecules identified are of higher (uptom/z400andabove). molecular mass than molecules usually identified through single pyrolysis, either due to the addition of silyl functional group(s) 3.4.2.MTBSTFAderivatization on the molecules, or because of the extraction and preservation Chemicalderivatizationreactionswerealsoperformedthaten- of high molecular weight molecules. A direct detection of amino ableanalysisoffragileorrefractorymolecules(Rosenbaueretal., acidsin thesamplesshows alaninederivatizedinsampleE3and 1999).Aderivatizationsolventtransformslesslabilepolarorganic prolineinsampleE2,atlowconcentration. compounds,suchasaminoacidsandcarboxylicacids,intovolatile SampleH3displaysthesamequalitativepatternuponderivati- tert-butyldimethylsilyl(tBDMS)derivativesthatcanbeseparated zationastheothertechniques(Fig.9),withmorederivatizedcar- andidentifiedbyGC/MS(Fig.8). boxylicacididentified.Themaincomponentofthesedimentafter Fig.7. ThechromatogramafterpyrolysisofsampleH3,fromtheanoxicregionofLakeHoareshowingmassdetectionfromm/z45to535.Onlypeaksthatwerenotalso detectedinsampleE2arerepresentedhere.Sulfurispresent,consistentwiththedetectionofpyritebymineralogicalstudies.Nitrogenisincorporatedintomanymore moleculesthaninE2,notablyasamines.Long-chaincarboxylicacidsareidentified,mostlywithanevennumberofcarbonatoms,whichsuggestsabioticorigin.Onthe contrary,onlyafewlowmolecularweightmoleculesarepresentinsampleE2withoutbeingseeninsampleH3. Fig.8. DerivatizationreactionwithMTBSTFA.Acarboxylicfunctionissilylatedbythereagentwithadditionofasolvent(DMF),whenreactedforafewminutesathigh temperature.Thelabilehydrogenisthusreplaced,andthereactivityoftheformerfunctionisabated. Pleasecitethisarticleinpressas:Bishop,J.L.,etal.CoordinatedanalysesofAntarcticsedimentsasMarsanalogmaterialsusingreflectancespectroscopy andcurrentflight-likeinstrumentsforCheMin,SAMandMOMA.Icarus(2012),http://dx.doi.org/10.1016/j.icarus.2012.05.014