Busemann, H.

Chapman, S.

Franchi, I.A.

Guillermier, C.

Henkel, T.

King, A.

Lee, M.

Lyon, I.C.

Rost, D.

English

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Enlighten – Research publications by members of the University of Glasgow 
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King, A., Henkel, T., Chapman, S., Busemann, H., Rost, D., Guillermier, 
C., Lee, M., Franchi, I.A., and Lyon, I.C. (2011) Amorphous Carbon 
Grains in the Murchison Meteorite. In: 42nd Lunar and Planetary Science 
Conference, March 7–11, 2011, Texas, USA. 
 
 
 
 
 
 
0B0Bhttp://eprints.gla.ac.uk/59738/ 
 
 
 
 
Deposited on: 6 February 2012 
 
 
AMORPHOUS CARBON GRAINS IN THE MURCHISON METEORITE. A. King1,4,5, T. Henkel1, S. Chap-
man1, H. Busemann1, D. Rost1, C. Guillermier2, M.R. Lee3, I.A. Franchi2 and I.C. Lyon1,   1School of Earth, Atmo-
spheric and Environmental Sciences, University of Manchester, Manchester M13 9PL,  2Planetary and Space Sci-
ences Research Institute, The Open University, Milton Keynes, MK7 6AA, 3School of Geographical and Earth Sci-
ences, University of Glasgow, Glasgow, G12 8QQ, 4present address: Department of Geophysical Sciences, Univer-
sity of Chicago, Chicago, IL 60637, 5Chicago Center for Cosmochemistry. (ajking@uchicago.edu)
Introduction:  During a search for presolar graph-
ite  grains  gently  separated  [1]  from  the  Murchison 
(CM2) meteorite, we discovered a set of micron-sized 
amorphous  carbonaceous  grains.  The  presence  of 
amorphous carbon has previously been reported in in-
soluble organic matter (IOM) [2], interplanetary dust 
particles (IDPs) [3] and cometary samples [4], as well 
as carbon flakes, nano-tubes and nano-globules [5,6]. 
However, it is still unclear as to how this amorphous 
carbon  was  formed  and  became incorporated  into  a 
wide range of primitive solar system materials.
Experimental:  Material from three size and dens-
ity aliquots, referred to as B4a, B4b (both containing 
grains 7–20μm and 2.15–2.26gcm-3), and C4a (1–7μm, 
2.15–2.26gcm-3),  were  deposited  onto  separate  Au-
foils. Carbonaceous grains were located on the foils us-
ing a secondary electron microscope (SEM) and energy 
dispersive  X-ray  analysis.  Ten  carbonaceous  grains 
were found in sample B4a,  14 in B4b and 9 in C4a 
(Figure 1).
Figure  1.  SEM  image  of  carbonaceous  grain  B4a-X-1 
(left)  and a  bright-field  TEM  image  of  the  same grain 
confirming its amorphous nature (right). 
TOFSIMS.  Six carbonaceous grains from B4a, and 
all from C4a, were measured for  12C/13C,  14N/15N and 
16O/18O using a time-of-flight secondary ion mass spec-
trometer (TOFSIMS). Carbon and N isotopes were de-
termined  by  measuring  CN-.  Mass  fractionation  was 
corrected by measuring terrestrial graphite.
NanoSIMS.  The 2D/1H, 12C/13C, 14N/15N and 16O/18O 
ratios of all  carbonaceous grains from B4b were ac-
quired using the NanoSIMS 50L at the Open Univer-
sity. In the first round of measurements negative sec-
ondary ions of C, O and CN were collected. During a 
second round of measurements negative 1H and 2D ions 
were collected, along with 12C as a control on grain po-
sition.  Mass  fractionation  was  corrected  using  well 
characterized IOM samples [7]. 
Raman Spectroscopy.   Raman analyses  were per-
formed  after  SIMS  measurements,  except  for  two 
grains that were not analyzed by SIMS. Spectra were 
obtained using a Horiba Scientific LabRAM 300 with a 
632nm He:Ne exciting laser. A 10x objective was used 
and the spot size of the laser was ~140μm with a power 
of ~70mW. Spectra were collected in the spectral range 
800–1800cm-1 in order to measure the D (“disordered”) 
and G (“graphite”) bands at ~1355cm-1 and 1581cm-1 
respectively. For calibration a graphite grain and well 
characterized IOM were also analyzed. 
TEM.   Foils for transmission electron microscopy 
(TEM) were prepared from three carbonaceous grains, 
two of which were milled to a thickness of ~100nm, the 
other ~200nm, using a FIB-SEM. Diffraction-contrast 
images and selected area electron diffraction (SAED) 
patterns  were  obtained  from the  foils  using  an  FEI 
Tecnai T20 TEM with a 200kV electron source.
Results:  Isotopes. The C, N and O isotopic com-
positions  of  nearly all  the  carbonaceous  grains  were 
solar within 1σ errors. Grain B4a-W-1 had a δ15N ratio 
of +1640 ± 430‰. All grains were typically enriched 
in D relative to SMOW, with δD values between +134 
to +333‰, and 1σ errors on average ~110‰. 
Raman. Figure 2 shows typical Raman spectra ob-
tained from graphite and IOM (used as standards, [2]), 
and from two carbonaceous grains.  Most grains (e.g. 
B4a-W-1, but also a grain not sputtered by SIMS) had 
very broad D and G band peak widths (ΓD and ΓG) con-
sistent with the presence of highly disordered carbon. 
In many cases the D and G bands overlapped, a com-
mon feature of amorphous carbon. Figure 3 shows ΓG 
as a function of peak position (ωG) in the grains. The 
ΓG values of the carbonaceous grains were often higher, 
and ωG lower, than those reported in IOM [2], IDPs [8] 
and cometary dust [4]. This suggests that they consist 
of carbon of  a  higher  degree  of disorder  than previ-
ously  observed  in  extra-terrestrial  samples.  Three 
grains had D and G band characteristics comparable to 
those measured in other primitive samples.
TEM.  Figure 1 includes a bright-field TEM image 
of  B4a-X-1.  It  is  featureless,  without  any diffraction 
contrast or internal structure. The SAED pattern con-
tained only very weak rings, with  a major d-spacing of 
~0.11nm. Images and patterns for the other two foils 
were similar, confirming the amorphous nature of the 
grains. We also note that all three grains had angles of 
~135° between outer surfaces suggesting that they had 
crystalline structures prior to amorphization.
2604.pdf42nd Lunar and Planetary Science Conference (2011)
Raman shift (cm-1)
800 1000 1200 1400 1600 1800
In
te
ns
ity
 (a
rb
. u
ni
ts
)
50
100
150
200
250
300
350
400
Raman shift (cm-1)
800 1000 1200 1400 1600 1800
In
te
ns
ity
 (a
rb
. u
ni
ts
)
550
600
650
700
750
800
850
900
950
Raman shift (cm-1)
800 1000 1200 1400 1600 1800
In
te
ns
ity
 (a
rb
. u
ni
ts
)
25000
30000
35000
40000
45000
50000
55000
Raman shift (cm-1)
800 1000 1200 1400 1600 1800
In
te
ns
ity
 (a
rb
. u
ni
ts
)
1000
1100
1200
1300
1400
1500
1600
Terrestrial Graphitie
D
-b
an
d
G
-b
an
d
Allende IOM
B4a-W-1 B4b-7-1
Figure  2.  Raman spectra  from graphite,  Allende  IOM, 
amorphous grain B4a-W-1, and the more ordered B4b-7-
1. Amorphous  carbon  produces  overlapping  D  and  G 
bands.
Discussion:  SIMS effects. Sputtering by high en-
ergy ion beams could have led to amorphization of the 
outer tens of nanometers of the grains. However, Ra-
man spectra  of  a  grain not  analyzed  by SIMS, were 
consistent  with amorphous carbon.  TEM results  also 
indicated that  the SIMS measurements did not cause 
the amorphization as grain cores, not just outer layers, 
were found to be amorphous (see Figure 1).
Origins.  The isotopically normal C, N and O com-
positions of the carbonaceous grains cannot prove cir-
cumstellar  environments  as  their  source.  Organic 
particles or mantles on grains in the ISM or proto-solar 
nebula can contain large (>10,000‰) D and  15N en-
richments from ion-molecule reactions and mass frac-
tionation processes [e.g. 9]. With the exception of B4a-
W-1 extreme D and 15N enrichments were not detected 
in  the  amorphous  carbonaceous  grains.  The  grains’ 
slight D enrichments are comparable to those measured 
in some IDPs [e.g. 10], indicating that they may have 
formed in similar environments. 
Amorphous carbon has previously been linked to 
Fischer-Tropsch reactions and precipitation of element-
al carbon onto metal grains in the early solar system 
[11]. We saw no evidence for metal sub-grains during 
either ESEM analysis or TOFSIMS measurements of 
several  grains  detecting  positive  secondary  ions. 
Amorphous  carbon  has  also  been  produced  through 
arc-discharge [12], although those grains were tens of 
nanometers  in  size,  much  smaller  than  the  carbon-
aceous grains reported here. 
Irradiation  experiments  using soot  or  carbon-ices 
show that under increasing bombardment with H+ and 
He+ ions these materials are converted to amorphous 
carbon  [13,14].  Figure  3  shows  that  Raman  spectra 
from soot irradiated with ion fluences of ~1015 – 1016 
ions cm-2 is very similar to that of the amorphous car-
bonaceous grains and also some IDPs. Such ion doses 
would have been easily achievable in the early solar 
system through the solar wind, which may have been 
up to 1000x stronger than present day conditions [15]. 
Irradiation of the carbonaceous grains in the solar wind 
should have implanted  H+ ions  causing a  dilution in 
any large D enrichment they initially acquired.
ω G (cm
-1)
1530 1540 1550 1560 1570 1580 1590 1600 1610
Γ G
 (c
m
-1
)
0
50
100
150
200
250
Meteoritic IOM
IDPs
Cometary materials
C grains
Irradiated Soot
Ion irradiation
Thermal Metamorphism
B4a-W-1
B4b-7-1
Figure 3. Raman G-band characteristics of carbonaceous 
grains compared to meteoritic IOM [2], IDPs [8], comet-
ary samples [4] and soots irradiated with H+ and He+ ions 
[14]. The ΓG and ωG of the soots evolved as a function of 
ion fluence, by increasing and decreasing respectively.
References:  [1] Tizard J. et al. (2005) Meteoritics  
& Planet.  Sci., 40,  335–342.  [2] Busemann H. et  al. 
(2007)  Meteoritics  &  Planet.  Sci., 42,  1387–1416. 
[3] Wopenka B. (1988) Earth & Planet. Sci. Lett., 88, 
412–425.  [4] Rotundi A. et  al.  (2008)  Meteoritics & 
Planet.  Sci., 43,  367–397.  [5]  Garvie  L.A.J.  and 
Buseck P.R.  (2004)  Earth & Planet.  Sci.  Lett.,  224, 
431–439.  [6]  Nakamura-Messenger  K.  et  al.  (2006) 
Science,  314, 1439–1442. [7] Alexander C.M.O’D. et 
al. (2007)  Geochim.  Et Cosmochim. Acta,  71,  4380–
4403. [8] Busemann H. et al. (2009)  Earth & Planet.  
Sci. Lett., 288, 44–57. [9] Millar T.J. et al. (1989) As-
trophys.  J.,  340,  906–920.  [10] Messenger S. (2000) 
Nature,  404,  968–971.  [11]  Brearley  A.J.  (1990) 
Geochim. Et Cosmochim. Acta, 54, 831–850. [12] Ro-
tundi A. et al. (1998) Astron. & Astrophys., 329, 1087–
1096. [13] Barrata G.A. et al. (2004)  J. Raman Spec-
trosc.,  35,  487–496.  [14]  Brunetto  R.  et  al.  (2009) 
Icarus,  200,  323–337.  [15]  Wood B.E.  et  al.  (2002) 
Astrophys. J., 574, 412–425.
Acknowledgements:   D. Blagburn and B.  Clem-
entson for TOFSIMS maintenance, V. Fawcett for the 
Raman spectrometry, B. Smith and C. How for the FIB 
and TEM with Prof. A. Craven providing access. The 
Science and Technology Facilities Council (STFC) is 
thanked  for  a  studentship  (AK),  research  position 
(TH), Aurora fellowship (HB), and the UKCAN pro-
gramme (DR) and (CG).
2604.pdf42nd Lunar and Planetary Science Conference (2011)


Amorphous Carbon Grains in the Murchison Meteorite

Enlighten

Enlighten – Research publications by members of the University of Glasgow http://eprints.gla.ac.uk       King, A., Henkel, T., Chapman, S., Busemann, H., Rost, D., Guillermier, C., Lee, M., Franchi, I.A., and Lyon, I.C. (2011) Amorphous Carbon Grains in the Murchison Meteorite. In: 42nd Lunar and Planetary Science Conference, March 7–11, 2011, Texas, USA.       0B0Bhttp://eprints.gla.ac.uk/59738/     Deposited on: 6 February 2012   AMORPHOUS CARBON GRAINS IN THE MURCHISON METEORITE. A. King1,4,5, T. Henkel1, S. Chap-man1, H. Busemann1, D. Rost1, C. Guillermier2, M.R. Lee3, I.A. Franchi2 and I.C. Lyon1,   1School of Earth, Atmo-spheric and Environmental Sciences, University of Manchester, Manchester M13 9PL,  2Planetary and Space Sci-ences Research Institute, The Open University, Milton Keynes, MK7 6AA, 3School of Geographical and Earth Sci-ences, University of Glasgow, Glasgow, G12 8QQ, 4present address: Department of Geophysical Sciences, Univer-sity of Chicago, Chicago, IL 60637, 5Chicago Center for Cosmochemistry. (ajking@uchicago.edu)Introduction:  During a search for presolar graph-ite  grains  gently  separated  [1]  from  the  Murchison (CM2) meteorite, we discovered a set of micron-sized amorphous  carbonaceous  grains.  The  presence  of amorphous carbon has previously been reported in in-soluble organic matter (IOM) [2], interplanetary dust particles (IDPs) [3] and cometary samples [4], as well as carbon flakes, nano-tubes and nano-globules [5,6]. However, it is still unclear as to how this amorphous carbon  was  formed  and  became incorporated  into  a wide range of primitive solar system materials.Experimental:  Material from three size and dens-ity aliquots, referred to as B4a, B4b (both containing grains 7–20μm and 2.15–2.26gcm-3), and C4a (1–7μm, 2.15–2.26gcm-3),  were  deposited  onto  separate  Au-foils. Carbonaceous grains were located on the foils us-ing a secondary electron microscope (SEM) and energy dispersive  X-ray  analysis.  Ten  carbonaceous  grains were found in sample B4a,  14 in B4b and 9 in C4a (Figure 1).Figure  1.  SEM  image  of  carbonaceous  grain  B4a-X-1 (left)  and a  bright-field  TEM  image  of  the  same grain confirming its amorphous nature (right). TOFSIMS.  Six carbonaceous grains from B4a, and all from C4a, were measured for  12C/13C,  14N/15N and 16O/18O using a time-of-flight secondary ion mass spec-trometer (TOFSIMS). Carbon and N isotopes were de-termined  by  measuring  CN-.  Mass  fractionation  was corrected by measuring terrestrial graphite.NanoSIMS.  The 2D/1H, 12C/13C, 14N/15N and 16O/18O ratios of all  carbonaceous grains from B4b were ac-quired using the NanoSIMS 50L at the Open Univer-sity. In the first round of measurements negative sec-ondary ions of C, O and CN were collected. During a second round of measurements negative 1H and 2D ions were collected, along with 12C as a control on grain po-sition.  Mass  fractionation  was  corrected  using  well characterized IOM samples [7]. Raman Spectroscopy.   Raman analyses  were per-formed  after  SIMS  measurements,  except  for  two grains that were not analyzed by SIMS. Spectra were obtained using a Horiba Scientific LabRAM 300 with a 632nm He:Ne exciting laser. A 10x objective was used and the spot size of the laser was ~140μm with a power of ~70mW. Spectra were collected in the spectral range 800–1800cm-1 in order to measure the D (“disordered”) and G (“graphite”) bands at ~1355cm-1 and 1581cm-1 respectively. For calibration a graphite grain and well characterized IOM were also analyzed. TEM.   Foils for transmission electron microscopy (TEM) were prepared from three carbonaceous grains, two of which were milled to a thickness of ~100nm, the other ~200nm, using a FIB-SEM. Diffraction-contrast images and selected area electron diffraction (SAED) patterns  were  obtained  from the  foils  using  an  FEI Tecnai T20 TEM with a 200kV electron source.Results:  Isotopes. The C, N and O isotopic com-positions  of  nearly all  the  carbonaceous  grains  were solar within 1σ errors. Grain B4a-W-1 had a δ15N ratio of +1640 ± 430‰. All grains were typically enriched in D relative to SMOW, with δD values between +134 to +333‰, and 1σ errors on average ~110‰. Raman. Figure 2 shows typical Raman spectra ob-tained from graphite and IOM (used as standards, [2]), and from two carbonaceous grains.  Most grains (e.g. B4a-W-1, but also a grain not sputtered by SIMS) had very broad D and G band peak widths (ΓD and ΓG) con-sistent with the presence of highly disordered carbon. In many cases the D and G bands overlapped, a com-mon feature of amorphous carbon. Figure 3 shows ΓG as a function of peak position (ωG) in the grains. The ΓG values of the carbonaceous grains were often higher, and ωG lower, than those reported in IOM [2], IDPs [8] and cometary dust [4]. This suggests that they consist of carbon of  a  higher  degree  of disorder  than previ-ously  observed  in  extra-terrestrial  samples.  Three grains had D and G band characteristics comparable to those measured in other primitive samples.TEM.  Figure 1 includes a bright-field TEM image of  B4a-X-1.  It  is  featureless,  without  any diffraction contrast or internal structure. The SAED pattern con-tained only very weak rings, with  a major d-spacing of ~0.11nm. Images and patterns for the other two foils were similar, confirming the amorphous nature of the grains. We also note that all three grains had angles of ~135° between outer surfaces suggesting that they had crystalline structures prior to amorphization.2604.pdf42nd Lunar and Planetary Science Conference (2011)Raman shift (cm-1)800 1000 1200 1400 1600 1800Intensity (arb. units)50100150200250300350400Raman shift (cm-1)800 1000 1200 1400 1600 1800Intensity (arb. units)550600650700750800850900950Raman shift (cm-1)800 1000 1200 1400 1600 1800Intensity (arb. units)25000300003500040000450005000055000Raman shift (cm-1)800 1000 1200 1400 1600 1800Intensity (arb. units)1000110012001300140015001600Terrestrial GraphitieD-bandG-bandAllende IOMB4a-W-1 B4b-7-1Figure  2.  Raman spectra  from graphite,  Allende  IOM, amorphous grain B4a-W-1, and the more ordered B4b-7-1. Amorphous  carbon  produces  overlapping  D  and  G bands.Discussion:  SIMS effects. Sputtering by high en-ergy ion beams could have led to amorphization of the outer tens of nanometers of the grains. However, Ra-man spectra  of  a  grain not  analyzed  by SIMS, were consistent  with amorphous carbon.  TEM results  also indicated that  the SIMS measurements did not cause the amorphization as grain cores, not just outer layers, were found to be amorphous (see Figure 1).Origins.  The isotopically normal C, N and O com-positions of the carbonaceous grains cannot prove cir-cumstellar  environments  as  their  source.  Organic particles or mantles on grains in the ISM or proto-solar nebula can contain large (>10,000‰) D and  15N en-richments from ion-molecule reactions and mass frac-tionation processes [e.g. 9]. With the exception of B4a-W-1 extreme D and 15N enrichments were not detected in  the  amorphous  carbonaceous  grains.  The  grains’ slight D enrichments are comparable to those measured in some IDPs [e.g. 10], indicating that they may have formed in similar environments. Amorphous carbon has previously been linked to Fischer-Tropsch reactions and precipitation of element-al carbon onto metal grains in the early solar system [11]. We saw no evidence for metal sub-grains during either ESEM analysis or TOFSIMS measurements of several  grains  detecting  positive  secondary  ions. Amorphous  carbon  has  also  been  produced  through arc-discharge [12], although those grains were tens of nanometers  in  size,  much  smaller  than  the  carbon-aceous grains reported here. Irradiation  experiments  using soot  or  carbon-ices show that under increasing bombardment with H+ and He+ ions these materials are converted to amorphous carbon  [13,14].  Figure  3  shows  that  Raman  spectra from soot irradiated with ion fluences of ~1015 – 1016 ions cm-2 is very similar to that of the amorphous car-bonaceous grains and also some IDPs. Such ion doses would have been easily achievable in the early solar system through the solar wind, which may have been up to 1000x stronger than present day conditions [15]. Irradiation of the carbonaceous grains in the solar wind should have implanted  H+ ions  causing a  dilution in any large D enrichment they initially acquired.ω G (cm-1)1530 1540 1550 1560 1570 1580 1590 1600 1610Γ G (cm-1)050100150200250Meteoritic IOMIDPsCometary materialsC grainsIrradiated SootIon irradiationThermal MetamorphismB4a-W-1B4b-7-1Figure 3. Raman G-band characteristics of carbonaceous grains compared to meteoritic IOM [2], IDPs [8], comet-ary samples [4] and soots irradiated with H+ and He+ ions [14]. The ΓG and ωG of the soots evolved as a function of ion fluence, by increasing and decreasing respectively.References:  [1] Tizard J. et al. (2005) Meteoritics  & Planet.  Sci., 40,  335–342.  [2] Busemann H. et  al. (2007)  Meteoritics  &  Planet.  Sci., 42,  1387–1416. [3] Wopenka B. (1988) Earth & Planet. Sci. Lett., 88, 412–425.  [4] Rotundi A. et  al.  (2008)  Meteoritics & Planet.  Sci., 43,  367–397.  [5]  Garvie  L.A.J.  and Buseck P.R.  (2004)  Earth & Planet.  Sci.  Lett.,  224, 431–439.  [6]  Nakamura-Messenger  K.  et  al.  (2006) Science,  314, 1439–1442. [7] Alexander C.M.O’D. et al. (2007)  Geochim.  Et Cosmochim. Acta,  71,  4380–4403. [8] Busemann H. et al. (2009)  Earth & Planet.  Sci. Lett., 288, 44–57. [9] Millar T.J. et al. (1989) As-trophys.  J.,  340,  906–920.  [10] Messenger S. (2000) Nature,  404,  968–971.  [11]  Brearley  A.J.  (1990) Geochim. Et Cosmochim. Acta, 54, 831–850. [12] Ro-tundi A. et al. (1998) Astron. & Astrophys., 329, 1087–1096. [13] Barrata G.A. et al. (2004)  J. Raman Spec-trosc.,  35,  487–496.  [14]  Brunetto  R.  et  al.  (2009) Icarus,  200,  323–337.  [15]  Wood B.E.  et  al.  (2002) Astrophys. J., 574, 412–425.Acknowledgements:   D. Blagburn and B.  Clem-entson for TOFSIMS maintenance, V. Fawcett for the Raman spectrometry, B. Smith and C. How for the FIB and TEM with Prof. A. Craven providing access. The Science and Technology Facilities Council (STFC) is thanked  for  a  studentship  (AK),  research  position (TH), Aurora fellowship (HB), and the UKCAN pro-gramme (DR) and (CG).2604.pdf42nd Lunar and Planetary Science Conference (2011)

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Amorphous Carbon Grains in the Murchison Meteorite

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