The concentrations of C and N in cometary particles are of interest in characterizing the regions where comets formed. One aim of this work is to analyze enough Stardust particles to draw meaningful statistical conclusions about their inventories of C and N. Toward that end we report recent studies of Stardust particles and related materials

Burchell, M. J.

Flynn, G. J.

Herzog, G. F.

Keller, L. P.

Khodja, H.

Lindsay, F.

Nakamura-Messenger, K.

Park, J.

Raepsaet, C.

Smith, T.

Taylor, S.

Westphal, A.

NASA Technical Reports Server

 CHARACTERIZATION OF 81P/WILD 2 PARTICLES C2067,1,111,6.0 and C2067,1,111,8.0.  T. Smith1, H. 
Khodja1, C. Raepsaet1, M. J. Burchell2, G. J. Flynn3, G. F. Herzog4, J. Park4, F. Lindsay4, K. Nakamura-Messenger5, 
L. P. Keller5, S. Taylor6, and A. Westphal7  1 Laboratoire d’Etude des Eléments Légers, UMR 3299 CEA-CNRS-
IRAMIS, Gif-sur-Yvette, France (thomas.smith@cea.fr), 2 U. Kent, Canterbury, Kent, CT2 7NH, UK 3 SUNY-
Plattsburgh, Plattsburgh NY 12901-2681, 4 Rutgers U., Piscataway, NJ 08854-8087, 5 ARES, NASA Johnson Space 
Center, Houston, TX 77058, 6 CRREL, 72 Lyme Road, Hanover, NH 03755, 7 SSL, U. California, Berkeley, 94720. 
Introduction: The concentrations of C and N in 
cometary particles are of interest in characterizing the 
regions where comets formed. One aim of this work is 
to analyze enough Stardust particles to draw 
meaningful statistical conclusions about their 
inventories of C and N. Toward that end we report 
recent studies of Stardust particles and related 
materials.  
Experimental methods: Table 1 lists the samples 
studied and the analyses done. Three particles 
C2067.1.111.6.0, 7.0, and 8.0 (henceforth C6.0, C7.0 
and C8.0) were extracted from aerogel and placed on 
diamond plates for FTIR analyses. Following the FTIR 
analyses, the particles were embedded in sulfur, and 
partly microtomed into several slices roughly ~70 nm 
thick, and then floated these slices onto molybdenum 
TEM grids with Si/SiO membrane backings and 
supplied by ESPI. The backings provided physical 
support for the particles and were thought to be thin 
enough not to add too much to the Si and O already 
present in the samples. Additional sections were placed 
on carbon film substrates for TEM analyses. After 
microtomy, the sulfur was sublimed and the remaining 
portions of the particles were pressed into high-purity 
indium foil for nuclear reaction analyses (NRA). To 
reduce NRA backgrounds, each TEM grid was 
mounted across the mouth of a small well drilled into 
an Al disk and lined with In foil. 
Reports that C and N survive in craters that Stardust 
particles made in Al on the spacecraft [1-2] encouraged 
us to attempt quantitative nuclear reaction analyses of 
residues of the amino acid glycine (NH2CH2COOH) 
shot into Al plates ~102 µm thick.  
Finally, [3] reported that analyses of reagent-grade 
KOCN and NaOCN by the NRA method when 
calibrated with SiO2 gave oxygen fractions ~25% 
higher than expected [3]. They speculated that the 
nuclear cross section adopted for the reaction 
16O(d,p0)17O in reducing the data might have been 
responsible for the difference. To test this hypothesis, 
we varied the proton-detection angle from 170°, the 
one at which we and [3] made measurements, to 
164.25°, the angle at which the 16O(d,p0)17O nuclear 
cross section had been measured. 
Results: Stardust fragments - Figure 1 shows 
SEM/EDAX images taken of C6.0 and C8.0 without 
carbon coating. The fragments are ~10 µm across. 
Signals from Si and O derived from aerogel and the 
background from the indium foil dominate the EDX 
spectra of both particles. We saw small signals due to 
C, Mg, and Fe for C6.0 and due to Mg, S, and Fe for 
C8.0.  
FTIR – Spectra for C6.0, C7.0 and C8.0 were 
obtained with the extracted particles placed on 
diamond substrates. The spectra are dominated by Si-O 
stretching features that are consistent with aerogel 
mixed with amorphous Mg-silicate. C6.0 shows weak 
features in the 3.4-µm region that are consistent with 
aliphatic C-H in hydrocarbons; these features are also 
present in the spectra from C7.0, but are weaker; we 
see no aliphatic C-H in particle C8.0. More quantitative 
analysis is difficult for whole particles as variable 
sample thickness complicates the interpretation of band 
depth ratios. 
TEM - TEM imaging and chemical mapping data 
for C6.0 and C8.0 show that both particles are mixtures 
of compressed aerogel and melt glass. Elemental maps 
have no C-rich hotspots. Vesicular melt glass that is 
compositionally heterogeneous with respect to Mg/Si 
ratio dominates in C6.0. The melt glass contains 
abundant nanophase Fe metal and sulfide inclusions. 
Some of the sulfide inclusions are Ni-rich. Particle 
C8.0 also contains abundandant vesicular melt glass 
Table 1.   
Sample Form Analyses 
C2067.1.111.6.0 in In NRA, EDX, 
FTIR, TEM 
C2067.1.111.6.12 TEM-Mo  
C2067.1.111.8.0 in In NRA, EDX, 
FTIR, TEM 
C2067.1.111.8.4 TEM-Mo  
C2067.1.111.7.1 TEM-Mo NRA 
C2067.1.111.7.8 TEM-Mo  
KOCN shot into aerogel keystone NRA 
Glycine shot into Al Al NRA 
 
 
Figure 1. SEM images of C6.0 and C8.0 
https://ntrs.nasa.gov/search.jsp?R=20120003307 2019-08-30T19:24:53+00:00Z
 with heterogeneous Mg/Si ratios and nanophase Fe 
metal inclusions; Fe-sulfide grains are rare.  
Nuclear reaction analyses – In order to improve 
data-reduction methods, we first re-analyzed several 
well-characterized samples under the same 
experimental conditions used previously. From the 
results, the detector solid angle was estimated to be 110 
msr, a value consistent with an independent Monte-
Carlo evaluation. When comparing experimental 
spectra with simulations based on known compositions, 
we observed good agreement for C and N with vitreous 
carbon, KOCN and K3Fe(CN)6 targets. Some 
discrepancies on O appear with SiO2, Al2O3 and 
glycine. For quartz and alumina, changing the detection 
angle from 170° to 164.25°, improved the agreement, 
at least for the high energy part of the spectrum. In 
particular, the simulated-to-experimental, integrated 
count ratio increased from 0.95 at 170° to 0.99 at 
164.25°, which we consider satisfactory. For glycine, 
we speculate that the observed differences could be 
explained by large losses of H and CO due to the 
interactions with the incoming beam. 
The areal densities and their Poisson errors for Si, 
O, C and N of several samples are given in Table 2. To 
correct for instrumental blanks and possible mounting 
blanks, map data (e.g., Figure 2) were divided in two 
parts, one containing the sample itself, and the 
second all the rest. Comparisons were made 
between the number of counts for each 
element in the “sample zone” and in the “blank 
zone”. The difference gives the effective 
number of counts to be simulated using 
SIMNRA program [4].  
Oxygen and silicon dominate the elemental 
compositions of Stardust particles C6.0, C6.12 
and C7.0, as in C23 and C41 in [3] and C21 in 
[5]. The Si/O atom ratio for particle C6.0 is 
close to the expected value of 0.5 for silica. 
For particle C8.0 the ratio is 0.39 which is 
about 20% lower than silica ratio. The 
observed Si/O ratios are consistent with the 
presence of aerogel mixed with some cometary 
material and affirm the SEM and FTIR 
measurements. Removal of the aerogel blank 
from the Stardust signal is calculated using the 
same procedure as described in [3] and [5]. It appears 
that for particle C8.0, most of the C concentration 
derives from aerogel. Nitrogen abundances are low for 
samples C6.0, C8.0 and C6.12, as in C2103 and C2065 
in [5]. In Stardust TEM C2067.1.111.7.1, the atom 
fraction of nitrogen is higher and represents 10.7%. 
The calculated C/N ratios increase from 3.3 in 
particles C6.1 and C7.12 to 43.6 in C6.0 whereas 
previous data obtained by [3] varied from 11 to 51 and 
from 8 to 14 in [6]. As a comparison, the C/N ratios are 
about 12.6 for CI chondrites and 20 for comets [3]. 
Great lability for N than for C [3] during impact with 
aerogel may have caused preferentially a loss of N on 
capture. If so, our calculated C/N ratios would be 
higher than those of the cometary particles before 
impact.  
Glycine craters – Glycine samples were shot into 
aluminum foils at 6.34 km/s so as to simulate the 
conditions occurring during Wild 2 particle capture. 
Information on dust velocity and density can be 
derived from these experiments [7]. We were able to 
process the data on one of the three examined samples, 
G150310. Results are given in Table 2. The C/N and 
O/C ratios are respectively 7.1 and 3.2 instead of 2.0 
expected from stoichiometry. These results indicate 
loss of light elements, even larger than for the glycine 
reference, probably due to the impact itself.  
References: [1] Stadermann F. J. et al. (2008) 
M&PS, 43, 299-313. [2] Kearsley A.T. et al. (2010) 
LPSC, 41, abstract #1971. [3] Gallien J-P. et al. (2008) 
M&PS, 43, 335-351. [4] Mayer M. (1997) Report IPP 
9/113. [5] Khodja H. et al. (2009) LPSC, 40, abstract 
#1746. [6] Cody G. et al. (2008) M&PS, 4, 353-365. 
[7] Kearsley A.T. et al. (2008) M&PS, 43, 41-73. 
Table 2.  Atomic areal density (1015 atom/cm2) by NRA. 
  Si O C N 
C6.0 
a 1139-26 15.7-0.8 25.2-4.7 59-12 
b 1317 2815 905 13 
c 0 182±2 558±6 13±3 
C8.0 
a 1473-96 23.4-1.8 9.86-5.97 44-32 
b 1024 2613 101 2 
c 0 565±5 0 2±2 
C7.1 
a 124-137 4.81-1.96 17.1-4.3 601-9 
b 86 599 478 140 
c 0 428±17 456±7 140±7 
C6.12 
a 179-156 2.40-1.10 5.92-4.30 77-12 
b 36 273 59 15 
c 0 201±13 50±4 15±3 
G150310 a  19.8-0.9 22.8-9.03 397-81 b 0 5004±107 1544±27 218±20 
a) Counts –background; O and C (×103). b) Areal density (×1015 at/cm2). 
c) Areal density less aerogel contribution (×1015 at/cm2).  
 
C O Si 
 
Figure 2. Stardust particle C6.0. Sample outlined in 
green  


Characterization of 81P/Wild 2 Particles C2067,1,111,6.0 and C2067,1,111,8.0

Characterization of 81P/Wild 2 Particles C2067,1,111,6.0 and C2067,1,111,8.0

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