New analyses of indigenous secondary material in the martian meteorite Nakhla reveal amorphous carbon-rich veins and dendrites. The texture and chemistry of this material resembles that of biogenically altered sub-ocean basaltic glasses

Clemett, S. J.

Gibson, E. K., Jr.

McKay, D. S.

Pillinger, C. T.

Rice, T.

Robert, F.

Thomas-Kerpta, K. L.

VanLeer, B.

Verchovsky, A. B.

Wentworth, S. J.

Wright, I. P.

English

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 meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the martian meteorites. [6 & 7] reported the presence 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 C-14, which is modern-day carbon. This C fraction 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 (approx.0.5 micron 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 microscopy, Laser Raman Spectroscopy, Nano-SIMS Ion Micro-probe, and Stepped-Combustion Static Mass Spectrometry

NASA Technical Reports Server

OBSERVATION 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. 
https://ntrs.nasa.gov/search.jsp?R=20080026354 2019-08-30T04:45:05+00:00Z
Fig 1. Optical views of Nakhla polished thin sections (above).  Left:  iddingsite veins in olivine. Isotopic
analyses were performed on this region. Right: cpx region containing optically dark, dendritic
features (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 dendritic
vein-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‰.   
Gibson et al.: Carbonaceous matter in Nakhla


Observation and Analysis of In Situ Carbonaceous Matter in Naklha

Thomas-Keprta, K. L.

Gibson Jr., E. K.

Van Leer, B.

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 IConference or Workshop ItemHow to cite:McKay, D. S.; Clemett, S. J.; Thomas-Keprta, K. L.; Wentworth, S. J.; Gibson Jr., E. K.; Robert, F.; Verchovsky, A.B.; Pillinger, C. T.; Rice, T. and Van Leer, B. (2006). Observation and analysis of in situ carbonaceous matter inNakhla: Part I. 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/2251.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 NAKHLA:  PART I.  D.S. McKay1, S.J. Clemett2, K.L. Thomas-Keprta2, S.J. Wentworth2, E.K. Gibson, Jr1, F. Robert3, A.B. Ver-chovsky4, C.T.Pillinger,4  T. Rice5, B. Van Leer5; 1Astrobiology Group, KA/ARES, NASA-JSC, Houston,  TX 77058;2 Astrobiology Group, ESCG, JE23, Johnson Space Center, Houston, TX 77058; 3Museum D’Histoire Naturelle, Paris, France; 4PSSRI, The Open University, Milton Keynes,  MK7 6AA, UK; 5FEI Company, Hillsboro, OR 97124.  Introduction:  We have made new surveys of thin sections of the martian meteorite Nakhla by petrographic microscope, laser Raman spectroscopy, NanoSims Ion Microprobe, and stepped combustion static mass spectroscopy.  We have also applied a computer technique that produces three-dimensional anaglyphs from a series of down-through-focus images in a standard petrographic thin section.  Here and in a companion abstract [1] we describe for the first time a new phase rich in carbon and also containing nitrogen. Nakhla thin sections always display secondary alteration consisting of corrosion of some minerals followed by partial or com-plete filling by indigenous secondary phases [2,3]. While olivine shows the greatest degree of corrosion and replace-ment, pyroxene and minor minerals such as apatitie and feld-spar also exhibit corrosion and replacement.  This new phase is closely associated with the iddingsite previously described as a major secondary replacement mineral in Nakhla [2,3].  Results:  Here, and in a companion paper [1] we report for the first time the presence of a carbon-rich indigenous phase in cracks and pores in Nakhla.  The analyzed carbonaceous material occurs as vein fillings (Figs. 1-4) in at least 3 dis-tinct, but related, morphologies.  Most prominent is “mas-sive” vein filling, which  completely occupies narrow veins ranging in width from  micrometers down to a fraction of a micrometer. The second type of occurrence is usually at-tached to the massive vein filling and consists of dendritic-like projections and tiny tubes usually attached on one side to the massive carbonaceous phase (Figs. 1-2).  These tubes are sometimes found in hollowed-out corrosion cavities where they appear to line the walls.  However, in 3d views, they are intimately interfingered with the host silicate near walls of cavities and cracks, and are not simply a coating; they appear to partially penetrate the silicate at the sub-nanometer level (Fig. 1c).  The third occurrence consists of small (0.2-2 μm), mostly circular blebs of nearly opaque material. While this material closely resembles the analyzed carbonaceous veins and is spatially associated with it, we do not have direct analysis to confirm whether it is identical in composition. EDX analysis of a vein segment extracted from a thin section by FIB preparation is shown in Figs. 3 and 4. These data clearly show that the vein is rich in C with minor amounts of Cl and S; Si may be from adjacent pyroxene.  The analyzed vein was taken from a region containing the dendritic material as well as the massive vein (Fig. 2), so the displayed composition likely includes the dendritic material as well. Discussion: This carbonaceous material cannot be the epoxy used in thin section preparation.  As shown in detail in [1], both NanoSIMS and laser Raman spectroscopy show distinct differences between the carbon/nitrogen ratio of the epoxy and of the carbonaceous vein; the laser Raman spectra of the vein is totally unlike that of the epoxy.  In addition, [1] argue that the carbon isotopes strongly support an interpretation that this carbon is indigenous to Mars and is very unlikely to be a terrestrial contaminant.  The carbon in this vein may be from infalling meteorites on Mars; recent work on carbona-ceous chondrites show the presence of nano-sized carbona-ceous particles containing both nitrogen and sulfur [4] but the close resemblance to the carbon found in subocean basal-tic glass alteration veins [5-7] provides a plausible basis for a hypothesis that the Nakhla carbonaceous material is bio-genic.  We propose in this alternative hypothesis that organic acids from microbes (possibly in a polysaccharide biofilm) produced the corrosion [8], and the remains of the biofilm and the included microbes provide a kerogen-like carbona-ceous material that fills the veins, provides the dendrites, fills the tiny tubes, and produces the small blebs.  Additional support for a biogenic hypothesis comes from recent analysis of known microfossils in Proterozoic Bitter Springs chert by NanoSIMS that show a close association between fossil morphology and carbon, nitrogen, and sulfur abundances [9]. References: [1] Gibson et al. (2006) this vol.; [2] Gooding et al. (1991) Meteoritics 26, 135-143; [3] Wentworth et al. (2006) Icarus 174, 383-395; [4] Garvie & Buseck (2004) EPSL 224, 431-439; [5] Fisk et al. (2006) AST  (in press); [6] Fisk et al (1998) Science 281, 978-980; [7] Thorseth et al. (1995) Chem. Geol.  126, 137-146; [8] Benzerara et al. (2005) PNAS  102, 979-982; [9] Oehler et al. (2006), this vol  Fig. 1. Optical views of polished section of Nakhla (right and left). Region in red box (right) is described in a com-plementary paper [1]. Region in blue box, (dark, dendritic) is morphologically identical to that located in the red box.  A section of this region was extracted using FIB and ana-lyzed using TEM and described herein. FIB section of vein-filled crack (lower left) imaged by FESEM.    Lunar and Planetary Science XXXVII (2006) 2251.pdfFigures 2 (left) & 3 (below): TEM studies of dendritic vein filling.  Element line scans (left) and EDX spectra (below) show that the vein-filling material is C-rich and contains minor S, Cl, P, and Si (Cu is from TEM grid; Ga and Pt from FIB section preparation).  Nakhla cpxspectrum is shown for comparison. TEM diffraction (not shown here) demonstrates that this C-rich phase is amorphous.Nakhla cpxNakhla vein-filllingFigure 4: Anaglyph (stereo) optical images of Nakhla; all scale bars = 10 μm.4A (left): Vein filled with carbonaceous material toward vein top, with dendriticbranches at a deeper level.4B (right): Blebs connected to more massive vein fillings.4C (bottom): Intricate 3D network of dendritic and tube-shaped forms connected to more massive vein fillings (far left and far right).Lunar and Planetary Science XXXVII (2006) 2251.pdf

Observation and analysis of in situ carbonaceous matter in Nakhla: Part I

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

Verchovsky, A. B

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 I

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