TOF-SIMS, NANOSIMS, AND TEM ANALYSIS OF INTERPLANETARY DUST PARTICLE SECTIONS. T. Stephan 1, I. Weber 1, and P. Hoppe 2, 1Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Ger-many, stephan@uni-muenster.de, 2Max-Planck-Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany.
Introduction: Before in 2006 the Stardust mission
will bring material from comet Wild 2 under con-trolled conditions to Earth [1], anhydrous IDPs repre-sent probably the only source for cometary matter that
is available for analysis in terrestrial laboratories. Like
meteorites, IDPs have their own individual history that
links them to their respective parent bodies and that
can be revealed with modern analytical techniques. In
most previous studies, only one analytical technique
has been applied to individual particles and averaged
properties from different sub-sets of the IDP collection
were compared. Major technical developments during
recent years provide the opportunity to study individ-ual particles with a great variety of analytical tech-niques.
In continuation of a comprehensive consortium
study of IDPs from stratospheric dust collector U2071
[2], three particles were selected for TOF-SIMS,
NanoSIMS, and TEM analysis. This suite of analytical techniques allows to obtain information on the elemen-tal, isotopic, and mineralogical composition of IDPs on a sub-micrometer scale. Since 1994, when the consor-tium study was initiated, technical improvements in both SIMS variants [3,4], especially in achievable lat-eral resolution and sensitivity have significantly en-hanced the abilities to study these tiny, extremely fine-grained, complex particles.
Samples and Analytical Techniques: The IDPs
selected for this study were U2071J2, U2071C9, and U2071H1h. All particles were previously characterized
at NASA Johnson Space Center by SEM including
bulk chemical analysis with EDS for major elements
(including C) and secondary electron imaging (Fig. 1).
After hexane rinsing to remove silicone oil residues
from particle collection and storage, the IDPs were
embedded in epoxy and ~80 nm thick microtome sec-tions were produced. Sectioning was stopped after slicing approximately one half of the respective IDPs. The residual epoxy stubs were used for TOF-SIMS analysis, whereas the different sections were selected for TEM and NanoSIMS investigation. Unfortunately, no material from U2071H1h was found in the micro-tome sections. Results and Discussion: Element ratios obtained by TOF-SIMS for sample sections are shown in Fig. 2. Individual secondary ion images are given in Figs. 3, 5, and 6. TOF-SIMS three color composite images, where red, green, and blue are assigned to the normal-ized intensities of Mg, Al, and Fe, are displayed in Figs. 4, 5, and 6. In Fig. 4 also a TEM overview image of U2071J2 is given. NanoSIMS results for O isotopes in U2071J2 and U2071C9 are discussed in [5].
10
-110010
110
2
A b u n d a n c e / C I (S i =1)
Fig. 2. Element ratios relative to Si and normalized to CI.
U2071J2. TOF-SIMS and TEM results (Figs. 3 and 4) yield typical sizes much lower than 1 μm for different phases within this heterogeneous IDP. Sev-eral of these grains can be identified as olivine, pyrox-ene, and Fe,Ni-sulfides. Al-rich areas are probably GEMS (glass with embedded metal and sulfides). Since there is no indication for the presence of hydrous minerals, U2071J2 can be classified as an anhydrous
IDP, a class that is often connected to comets. How-ever, NanoSIMS results show no indication of isotopic
anomalies in oxygen or the presence of presolar matter [5]. Most element ratios relative to Si are below 1, an indication for the presence of residual silicone oil. Fig. 1. SEM secondary elec-tron images of three IDPs
from collection surface
U2071. U2071H1h is a piece
of U2071H1 that broke up
during previous particle handling [2].
U2071C9 also shows heterogeneities on a sub-micrometer scale (Fig. 5). Olivine, pyroxene, and some
Al-rich phases (probably feldspar, one also enriched in S) were identified by TOF-SIMS and TEM. Nano-SIMS analyses again show no isotopic anomalies [5].
U2071H1h mainly consists of a single Mg-rich phase (Fig. 6). Onion shell like distributions of OH, F,
and S (Fig. 6) are strong hints for contamination [6]. 1.54E6
23Na +7201.98E624Mg +433 2.39E527Al +168 3.18E528Si +1248.40E439K +43 2.80E540Ca +212 2.11E3
48Ti +42.21E452Cr +13 1.48E4
55Mn +113.46E616O -561OH 1.44E6-273 3.40E619F -4217.40E4
32S -761.40E535Cl -31Mg Al
Fe 56Fe +1103.36E558Ni +97.75E3
Acknowledgements: We thank U. Heitmann for microtome sectioning.
References: [1] Brownlee D. E. et al. (2003) JGR, 108, E8111. [2] Stephan T. et al. (2001) LPS 32, #1267. [3] Stephan T. (2001) Planet. Space Sci., 49, 859–906. [4] Hoppe P. (2002) New Astron. Rev., 46, 589–595. [5] Hoppe P. et al. (2005) LPS 36, #1301. [6] Stephan T. et al. (1994) LPS 25,
1341–1342.
1.10E624Mg +433 1.40E527Al +79 6.23E528Si +3816339K + 1.13E5448Ti + 1.69E3
1.25E452Cr +12 1.21E455Mn +10 3.87E556Fe +18014840Ca + 1.23E57.96E3
58Ni +111.25E616O -390 1.16E6
23Na +414OH 3.53E5-161 2.14E619F -335 5.17E4
32S -262235Cl -
1.44E5
Fig. 5. TOF-SIMS images of U2071C9 (14×14 μm 2
).
2.67E616O -759OH 1.14E6-340 1.05E619F -210 6.10E3
32S -72.28E5
23Na +2561.39E624Mg +463 2.20E427Al +368.97E428Si +518.44E339K +10 1.55E4
40Ca +23
55Mn +75.94E356Fe +407.10E4
Mg Al
Fe
Fig. 3. TOF-SIMS secondary ion images of U2071J2. Field of view is 13×13 μm 2. All images use the same linear color scale normalized to the most intense pixel. Below each image
numbers for maximum and integrated intensities are given.
Mg Al Fe
Fig. 4. TEM overview image (bright field, left) and TOF-SIMS composite image (right) of U2071J2.
Fig. 6. TOF-SIMS images of U2071H1h (7.5×7.5 μm 2).