Analysis of in situ carbonaceous matter in the Nakhla SNC meteorite has been carried out using a variety of techniques. Laser raman data shows the carbonaceous matter to be highly complex and static mass spectrometry has shown it to have an isotopic composition of '18 to '20' C

Clemett, S. J.

Gibson Jr., E. K.

McKay, D. S.

Pillinger, C. T.

Rice, T.

Robert, F.

Thomas-Keprta, K. L.

Van Leer, B.

Verchovsky, A. B

Wentworth, S. J.

Wright, I. P.

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsObservation and analysis of in situ carbonaceousmatter in Nakhla: part IIConference or Workshop ItemHow to cite:Gibson Jr., E. K.; Clemett, S. J.; Thomas-Keprta, K. L.; McKay, D. S.; Wentworth, S. J.; Robert, F.; Verchovsky, A.B; Wright, I. P.; Pillinger, C. T.; Rice, T. and Van Leer, B. (2006). Observation and analysis of in situ carbonaceousmatter in Nakhla: part II. In: 37th Lunar and Planetary Science Conference, 13-17 Mar 2006, Houston, Texas, USA.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2039.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukOBSERVATION AND ANALYSIS OF IN SITU CARBONACEOUS MATTER IN NAKLHA:  PART II.  E.K. Gibson, Jr1., S.J. Clemett2, K.L. Thomas-Keprta2, D.S.  McKay1, S.J. Wentworth2, F. Robert3, A.B. Ver-chovsky4, I.P. Wright4, C.T.Pillinger4, T. Rice5 and B. Van Leer5; 1KR, ARES, NASA-JSC, Houston,  TX 77058; 2ESCG, Mail Code JE23, Johnson Space Center, Houston, TX 77058; 3LEME, CNRS-Museum D’Histoire Naturelle, Paris, France; 4PSSRI, The Open University, Milton Keynes,  MK7 6AA, UK, 5FEI Company, Hillsboro, OR 97124 (everett.k.gibson@nasa.gov)   The search for indigenous carbon components on Mars has been a challenge.  The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1].  After the discovery that the SNC meteor-ites were from Mars [2], [3-5] reported C isotopic composi-tional information which suggested a reduced C component present in the martian meteorites.  [6 & 7] reported the pres-ence of reduced C components (i.e., polycyclic aromatic hydrocarbons) associated with the carbonate globules in ALH84001.   Jull et al. [8] noted in Nakhla there was an acid insoluble C component present with more than 75% of its C lacking any 14C, which is modern-day carbon.  This C frac-tion was believed to be either indigenous martian or ancient meteoritic carbon.   Fisk et al. [9, 10] have shown textural evidence along with C-enriched areas within fractures in Nakhla and ALH84001.  To further understand the nature of possible indigenous reduced C components, we have carried out a variety of measurements on martian meteorites.  For this presentation we will discuss only the Nakhla results.  Interior samples from the Nakhla SNC meteorite, recently made available by the British Museum of Natural History, were analyzed.  Petrographic examination [11, McKay et al., this volume] of Nakhla showed evidence of fractures (~0.5 μm wide) filled with dark brown to black dendritic material [Fig. 1] with characteristics similar to those observed by [10].  Iddingsite is also present along fractures in olivine.  Fracture filling and dendritic material was examined by SEM-EDX, TEM-EDX, Focused Electron Beam micros-copy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry.  Observations from the first three techniques are discussed in [11].  Nano-SIMS Ion Microprobe studies of the C-bearing frac-tures, containing the optically dark dendritic material, show direct correlation between C- and CN- abundances.  Ion abundances for epoxy are distinct from those of the dendritic material [Fig. 2].   Laser Raman Spectrometry was utilized to examine the optically dark dendritic material prior to stepped- combus-tion [Fig. 3].  Samples of the epoxy were examined along with the 100 - 150 μm diameter cores.  Individual 3 - 5 μm size regions within the cores were analyzed in the 1000 - 2000 wavenumber (cm-1) region.  Bands observed include: 1868, 1705, 1500, 1450, 1435, 1385, 1350, 1267, 1147, 1076 and 1045 wavenumber (cm-1) [Fig. 3].  This is the first re-port of an apparent complex mixture of carbonaceous com-ponents associated with Nakhla dendritic material and id-dingsite.  Stepped Combustion Static Mass Spectrometry analysis is capable of distinguishing different C- and N-bearing compo-nents present along with their C and N isotopic composi-tions. Analysis of epoxy blanks along with cored samples bearing the opaque carbonaceous-rich materials were ana-lyzed.  Three distinct components were detected in Nakhla.  A low-temperature C component released below 300oC was predominately terrestrial contamination with an isotopic composition of –22 to –24‰. A reduced C-bearing compo-nent with isotopic compositions of -16.1‰ to -18.4‰ to -20.2‰ to -19.4 ‰ was measured for the 400o, 450o, 500o and 550oC temperature intervals, resp.  Possible presence of a pre-terrestrial secondary carbonate with an isotopic composi-tion of >+5‰ was released at T > 550oC, but this phase is also similar to operational blanks.  The isotopic composition of the reduced C-component was identical to values -18 to -20‰ reported by [8] and [12].  However, our C analysis is the first isotopic measurement of directly imaged high mo-lecular weight carbonaceous components in Nakhla.  Previ-ous measurements were from bulk Nahkla samples with no direct observation of the C-bearing phases.  N isotopic com-position associated with the reduced C-component was ~+5‰.   This is the first report correlating fracture-fill material in Nakhla, iddingsite and optically dark dendritic material, with reduced carbonaceous components. The source of these components can be interpreted as produced by different pos-sible processes: (a) C introduced during a carbonaceous-rich impactor on Mars 600,000 to 700,000 years ago [13] -- this impact may have produced the fractures in Nakhla where iddingsite resides; or, (b) these C-bearing components may be products of biogenic activity and introduced by ground-water into the fracture features in Nakhla [14].     References: [1] Biemann K. et al., (1977) J.G.R. 82, 4641-4658. [2] Bo-gard D.D. and P. Johnson (1983) Science 221, 651-654. [3] Carr R.H. et al. (1985). Nature 314, 248-250. [4] Wright I.P. et al. (1989) Nature 340, 220-222. [5] Grady M.M. et al. (1994) Meteor.Planet. Sci. 24, 469. [6] McKay D.S. et al. (1996) Science 273, 924-930. [7] Clemett S.J. et al., Faraday Discuss. 109, 417-436. [8] Jull A.T.J. et al. (2000) GCA 64, 3763-3772. [9] Fisk M.R. et al., (2005) LPSC XXXVI, Abst. 2275. [10] Fisk M.R. et al., (2006) Astrobiology (in press). [11] McKay D.S. et al. (2006) LPSC XXXVII (this volume). [12] Sephton M.A. (2002) Planet. Space Sci. 50, 711-716. [13] Swindle T.D. and E.K. Olson (2004) Meteor. Planet. Sci. 39, 755-766. [14] Romanek C.R. et al., (1998) Meteor. Planet. Sci. 33, 775-784. Lunar and Planetary Science XXXVII (2006) 2039.pdfFig 1. Optical views of Nakhla polished thin sections (above).  Left:  iddingsite veins in olivine. Isotopicanalyses were performed on this region. Right: cpx region containing optically dark, dendriticfeatures (red box) (see complementary abstract by McKay et al., this volume, for chemical composition).  NanoSIMs analyses were performed on this region.Fig 2.  NanoSIMs analyses of epoxy and dendriticvein-filling material (above) showing that both are composed of carbon with distinctly different CN-/C-ratios.  NanoSIMs maps (right)  of dendritic material show  the distribution of C- and CN- ions.  Fig 3 (Left). Laser raman spectra of carbonaceous vein-filling material (red), CPX substrate (green),and epoxy embedding material (blue).  Vein-filling material appears to contain a complex mixture of carbon compounds with isotopic composition C ≈ -18 to -20‰.   Lunar and Planetary Science XXXVII (2006) 2039.pdf

Observation and analysis of in situ carbonaceous matter in Nakhla: part II

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Observation and analysis of in situ carbonaceous matter in Nakhla: part II

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