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TOF‐SIMS analysis of cometary matter in Stardust aerogel tracks
Abstract
Abstract— Cometary matter in aerogel samples from the Stardust mission was investigated with TOF-SIMS for its elemental and organic composition. While single grains >1 μm are highly variable in their chemical composition, nanometer-scale material found in the wall of one track has within a factor of 1.22 bulk CI chondritic element ratios relative to Fe for Na, Mg, A1, Ti, Cr, Mn, and Co. Compared to CI, a depletion in Ca by a factor of four and an enrichment in Ni by a factor of two was observed. These results seem to confirm recent reports of a CI-like bulk composition of Wild 2. The analysis of organic compounds in aerogel samples is complicated by the presence of contaminants in the capture medium. However, polycyclic aromatic hydrocarbons that could possibly be attributed to the comet were observed.
... TOF-SIMS has been a technique of choice for studying surface chemistry in the medical, materials science, and more recently cosmochemistry fields. It was chosen for this study for its utility in detecting oxide and hydroxide species with unparalleled detection sensitivity and spatial resolution (i.e., Chusuei et al. 1999;Cizaire et al. 2004;Rost et al. 1999;Stephan 2001;Stephan et al. 2003Stephan et al. , 2008aStephan et al. , 2008bToporski et al. 2002;Zhang et al. 2004). There have been numerous previous investigations that relied on the TOF-SIMS technique for determination of the presence or absence of hydroxyl in phosphates, including fluorapatite. ...
... However, this contamination was removed from the surface prior to analysis by pre-sputtering with an Ar + ion-beam. This technique is a standard technique for removing atomic monolayers of material from sample surfaces prior to analysis (i.e., Stephan 2001;Stephan et al. 2008b). The ion counts for a range of common contaminants on each of the analysis targets were monitored until a baseline number of counts was reached (Fig. 1). ...
... Each measurement consisted of ~50-150 scans, dependent on total ion yield, which corresponded to total measurement times of ~10-20 min. Further details of the TOF-SIMS technique and this TOF-SIMS instrument are given by Stephan (2001) and Stephan et al. (2008b). ...
Fluorapatite grains from Apollo 15 Mare basalt 15058,128 were analyzed by Raman spectroscopy, Raman spectral imaging, time-of-flight
secondary ion mass spectrometry (TOF-SIMS), field emission scanning electron microscopy (FE-SEM), and electron probe microanalysis
(EPMA) in an attempt to detect structurally bound OH− in the fluorapatite. Although OH− could not be definitively detected by Raman spectroscopy because of REE-induced photoluminescence, hydroxyl was detected
in the fluorapatite by TOF-SIMS. The TOF-SIMS technique is qualitative but capable of detecting the presence of hydroxyl even
at trace levels. Electron microprobe data indicate that on average, F and Cl (F+Cl) fill the monovalent anion site in these
fluorapatite grains within the uncertainties of the analyses (about 0.07 ± 0.01 atoms per formula unit). However, some individual
spot analyses have F+Cl deficiencies greater than analytical uncertainties that could represent structural OH−. On the basis of EPMA data, the fluorapatite grain with the largest F+Cl deficiency constrains the upper limit of the OH− content to be no more than 4600 ± 2000 ppm by weight (the equivalent of ~2400 ± 1100 ppm water). The TOF-SIMS detection of
OH− in fluorapatite from Apollo sample 15058,128 represents the first direct confirmation of structurally bound hydroxyl in a
lunar magmatic mineral. This result provides justification for attributing at least some of the missing structural component
in the monovalent anion site of other lunar fluorapatite grains to the presence of OH−. Moreover, this finding supports the presence of dissolved water in lunar magmas and the presence of at least some water
within the lunar interior.
... The particles show clear evidence for melting and mixing with molten aerogel. This is typical of strongly altered particles which are frequently found in dust extracted from Stardust track in aerogel Zolensky et al. 2008b). In the ternary Fe-Mg-S diagrams, the compositions are distributed along a line which joins the Mg corner and the average Fe/S relative composition of the Fe-Ni-S nanophases. ...
... They found an average S/Fe ratio = 0.46, which is very close to CI. Comparable values were also deduced by EDS-TEM measurements on thermally modified material extracted from different tracks by Leroux et al. (2008Leroux et al. ( , 2009. A CI-like composition is also supported by TOF-SIMS analyses (Stephan et al. 2008a(Stephan et al. , 2008b and is also suggested by the distribution of olivine compositions in Wild 2 grains (Zolensky et al. 2008b). ...
... They found an average S/Fe ratio = 0.46, which is very close to CI. Comparable values were also deduced by EDS-TEM measurements on thermally modified material extracted from different tracks by Leroux et al. (2008Leroux et al. ( , 2009. A CI-like composition is also supported by TOF-SIMS analyses (Stephan et al. 2008a(Stephan et al. , 2008b and is also suggested by the distribution of olivine compositions in Wild 2 grains (Zolensky et al. 2008b). ...
Abstract— Four particles extracted from track 80 at different penetration depths have been studied by analytical transmission electron microscopy (ATEM). Regardless of their positions within the track, the samples present a comparable microstructure made of a silica rich glassy matrix embedding a large number of small Fe-Ni-S inclusions and vesicles. This microstructure is typical of strongly thermally modified particles that were heated and melted during the hypervelocity impact into the aerogel. X-ray intensity maps show that the particles were made of Mg-rich silicates (typically 200 nm in diameter) cemented by a fine-grained matrix enriched in iron sulfide. Bulk compositions of the four particles suggest that the captured dust particle was an aggregate of grains with various iron sulfide fraction and that no extending chemical mixing in the bulb occurred during the deceleration. The bulk S/Fe ratios of the four samples are close to CI and far from the chondritic meteorites from the asteroidal belt, suggesting that the studied particles are compatible with chondritic-porous interplanetary dust particles or with material coming from a large heliocentric distance for escaping the S depletion.
... Tomeoka et al. (2008) reported textural zoning in allocation C2027-2-69-1-4 that has (1) a core of Wild 2 olivine and pyroxene minerals, (2) a (partial) rim of Si-O-Al-rich vesicular glass shards with variable amounts of Mg and Fe and with numerous electron-opaque Fe-Ni-S inclusions, and (3) an outer highly porous zone that is (flown) silica aerogel. Similar sharp glass-aerogel contacts are reported by Stephan et al. (2008) and Leroux et al. (2008), who also described transitions from pristine to densified (flown) aerogel and compressed aerogel. The contacts between these transitional forms are generally also sharp. ...
... Melting density-graded aerogel causes elements concentration and homogenization of particulate contaminants in silica melt. Several studies tried to establish contaminant backgrounds in the post-flight aerogel matrix using TOFF-SIMS and Synchrotron X-ray microbe analyses (Flynn et al. 2006; Ishii et al. 2008a; Lanzirotti et al. 2008; Stephan et al. 2008). So far, no chemically homogenous background was reported. ...
... Chlorine in flight aerogel of this allocation is enigmatic, as it was not listed among the elements present in pristine aerogel although chlorine is associated with aerogel in some Stardust samples (Ishii et al. 2008a). The overall patterns of the aerogel background abundances in allocation C2092,2,80,47,6, and in the aerogel backgrounds of allocation C2115,34,21,0; slice 6 (Stephan et al. 2008) and track C2115,19 (Lanzirotti et al. 2008), are similar (Fig. 4). There are differences. ...
Abstract— Flight aerogel in Stardust allocation C2092,2,80,47,6 contains percent level concentrations of Na, Mg, Al, S, Cl, K, Ca, Cr, Mn, Fe, and Ni that have a distinctive Fe- and CI-normalized distribution pattern, which is similar to this pattern for ppb level chemical impurities in pristine aerogel. The elements in this aerogel background were assimilated in non-vesicular and vesicular glass with the numerous nanometer Fe-Ni-S compound inclusions. After correction for the background values, the chemical data show that this piece of comet Wild 2 dust was probably an aggregate of small (<500 nm) amorphous ferromagnesiosilica grains with many tiny Fe,Ni-sulfide inclusions plus small Ca-poor pyroxene grains. This distinctive Fe- and CI-normalized element distribution pattern is found in several Stardust allocations. It appears to be a common feature in glasses of quenched aerogel melts but its exact nature is yet to be established.
... However, during data evaluation it became clear that one sample was relatively enriched in Fe, making it unsuitable as the general standard, whereas the main elemental ratios relative to Mg were all approximately chondritic.The amount of aerogel in each sample can be assessed by assuming a chondritic Si/Mg ratio (0.931;Anders and Grevesse 1989) for the sample, and attributing the excess Si to aerogel. Although Stardust aerogel is known to be contaminated with traces of elements other than Si and O (Tsou et al. 2003), no blank correction was applied, in contrast with the one used in a companion study, where cometary matter was analyzed directly in aerogel tracks (Stephan et al. 2008). There, element ratios in the aerogel blank were found to vary by up to a factor of five, even for samples from the same aerogel cell, and up to a factor of 60, when samples from different cells are compared. ...
... This neither implies that Wild 2 dust is expected to be mineralogically similar to CI chondrites, nor does this introduce a preconception regarding Wild 2 element ratios. Since no reliable blank correction was possible, it has to be noted that the quantitative analysis of some elements may be compromised based on the contamination observed in other Stardust aerogel samples (Stephan et al. 2008). Taking these observations into account, up to 100% of the measured Li and Sc, up to 84% of the V, and up to 63% of the K in the present study can be attributed to the aerogel. ...
... 12. For this correction, the span of trace element abundances observed in three aerogel samples (Stephan et al. 2008) was taken into account. Element data for Cu, Rb, Sr, and Ba are only provided inTable 2, because these trace element data lie clearly above CI and are probably due to contamination. ...
Abstract— Sections of seven cometary fragments extracted from the aerogel collector flown on the Stardust mission to comet 81P/Wild 2 were investigated with TOF-SIMS. These grains showed a rather heterogeneous chemical and mineralogical composition on a submicrometer scale. However, their average chemical composition is close to bulk CI chondritic values, which is consistent with analyses of numerous Stardust samples using various techniques. As a result, the TOF-SIMS analyses support the conclusion that Wild 2 has a CI-like bulk composition. The cometary particles resemble anhydrous chondritic porous interplanetary dust particles, which have previously been suggested to originate from comets. For one of the fragments, polycyclic aromatic hydrocarbons that could possibly be attributed to the comet were observed.
... The internal texture of the partially melted AMMs resembles that of the cometary Wild 2 sample captured in aerogel. comparison of AMMs with Wild 2 samples, we will use previously published Wild 2 data ( McKeegan et al. 2006; Sandford et al. 2006; Zolensky et al. 2006; Cody et al. 2008; Gallien et al. 2008; Glavin et al. 2008; Ishii et al. 2008b Leitner et al. 2008; Leroux et al. 2008b Leroux et al. , 2008c Matrajt et al. 2008; Nakamura et al. 2008a; Nakamura et al. 2008b; Simon et al. 2008; Stephan et al. 2008a Stephan et al. , 2008b Tomeoka et al. 2008; Zolensky et al. 2008).Figure 3 compares the average major and minor element contents of CONCORDIA AMMs with that of comet Wild 2 for samples collected both in aerogel and in crater residues. In an attempt to reduce analytical and sampling limitations, we have compiled and averaged all available compositional data for Wild 2 samples.Figure 3 (top) compares the Fe-and CInormalized compositions of AMMs and Wild 2 samples in aerogel (CI data from Lodders 2003; Wild 2 data from Ishii et al. 2008b; Lanzirotti et al. 2008; Leroux et al. 2008b; Stephan et al. 2008b). ...
... comparison of AMMs with Wild 2 samples, we will use previously published Wild 2 data ( McKeegan et al. 2006; Sandford et al. 2006; Zolensky et al. 2006; Cody et al. 2008; Gallien et al. 2008; Glavin et al. 2008; Ishii et al. 2008b Leitner et al. 2008; Leroux et al. 2008b Leroux et al. , 2008c Matrajt et al. 2008; Nakamura et al. 2008a; Nakamura et al. 2008b; Simon et al. 2008; Stephan et al. 2008a Stephan et al. , 2008b Tomeoka et al. 2008; Zolensky et al. 2008).Figure 3 compares the average major and minor element contents of CONCORDIA AMMs with that of comet Wild 2 for samples collected both in aerogel and in crater residues. In an attempt to reduce analytical and sampling limitations, we have compiled and averaged all available compositional data for Wild 2 samples.Figure 3 (top) compares the Fe-and CInormalized compositions of AMMs and Wild 2 samples in aerogel (CI data from Lodders 2003; Wild 2 data from Ishii et al. 2008b; Lanzirotti et al. 2008; Leroux et al. 2008b; Stephan et al. 2008b). All compositions inFig. ...
... Only a few assemblages showing a porphyritic texture have been found in AMMs up to now (Walter et al. 1995a; Kurat et al. 1996).Fig. 3. Fe-and CI-, and Si and CI-normalized abundances of the average composition of CONCORDIA micrometeorites (black diamonds) compared to the abundances of Wild 2 samples taken from the aerogel (open triangles in top diagram, data from Ishii et al. 2008b; Lanzirotti et al. 2008; Leroux et al. 2008b; Stephan et al. 2008b) and from crater residues (open circles in lower diagram, data from Kearsley et al. 2008; Leitner et al. 2008; Leroux et al. 2008c). To explain the observed low concentration of chondrules in AMMs, it has been proposed that coarse-grained AMMs may be related to fragments of chondrules (Walter et al. 1995a; Genge et al. 2005) (seeFig. ...
Abstract— We discuss the relationship between large cosmic dust that represents the main source of extraterrestrial matter presently accreted by the Earth and samples from comet 81P/Wild 2 returned by the Stardust mission in January 2006. Prior examinations of the Stardust samples have shown that Wild 2 cometary dust particles contain a large diversity of components, formed at various heliocentric distances. These analyses suggest large-scale radial mixing mechanism(s) in the early solar nebula and the existence of a continuum between primitive asteroidal and cometary matter. The recent collection of CONCORDIA Antarctic micrometeorites recovered from ultra-clean snow close to Dome C provides the most unbiased collection of large cosmic dust available for analyses in the laboratory. Many similarities can be found between Antarctic micrometeorites and Wild 2 samples, in terms of chemical, mineralogical, and isotopic compositions, and in the structure and composition of their carbonaceous matter. Cosmic dust in the form of CONCORDIA Antarctic micrometeorites and primitive IDPs are preferred samples to study the asteroid-comet continuum.
... Because of the high speed collection of the samples, the light elements could not be quantified, and volatile elements like S probably were redistributed around the tracks . Other elements show a chondritic composition within a factor of two Ishii et al. 2008;Lanzirotti et al. 2008;Leroux et al. 2008;Stephan 2008;Stephan et al. 2008). The bulk composition of cometary dust as discussed here is displayed in Fig. 3, with the abundances normalized to Fe and to CI. ...
... It could also represent a collection bias of dust from a portion of the coma which was poor in carbon and not representative of the whole comet (Westphal et al. 2017). (Jessberger et al. 1988), 81P/Wild 2 in aerogel Ishii et al. 2008;Lanzirotti et al. 2008;Leroux et al. 2008;Stephan 2008;Stephan et al. 2008), 67P/Churyumov-Gerasimenko (67P/C-G) , for 10 ultracarbonaceous Antarctic micrometeorites (UCAMMs) (Dartois et al. 2018, and unpublished data) and for 115 chondritic anhydrous IDPs (CA-IDPs) (Thomas et al. 1993;Keller et al. 2004;Schramm et al. 1989) (not all elements were measured for all CA-IDPs, see text). Error bars represent the variation range of the elemental compositions among cometary dust particles for the CA-IDPs and UCAMMs samples and for comets 1P/Halley and 81P/Wild2. ...
Cometary dust particles are best preserved remnants of the matter present at the onset of the formation of the Solar System. Space missions, telescopic observations and laboratory analyses advanced the knowledge on the properties of cometary dust. Cometary samples were returned from comet 81P/Wild2 by the Stardust mission. The chondritic (porous) anhydrous interplanetary dust particles and chondritic porous micrometeorites, and the ultracarbonaceous Antarctic micrometeorites (UCAMMs) also show strong evidence for a cometary origin. The composition of cometary dust is generally chondritic, but with high C and N compared with CI. The cometary organic matter is mixed with minor amounts of crystalline and amorphous minerals. The most abundant crystalline minerals are ferromagnesian silicates, refractory minerals and low Ni Fe sulfides are also present. The presence of carbonates in cometary dust is still debated, but a phyllosilicate-like phase was observed in a UCAMM. GEMS phases are usually abundant. Some of the organic matter present in cometary dust particle resembles the insoluble organic matter present in primitive meteorites, but amorphous carbon and exotic (e.g. N-rich) organic phases are also present. The H isotopic composition of the organic matter traces a formation at very low temperatures, in the protosolar cloud or in the outer regions of the protoplanetary disk. The presolar dust concentration in cometary dust can reach about 1%, which is the most elevated value observed in extraterrestrial samples. The differential size distribution of cometary dust in comet trails is well represented by a power-law distribution with a mean power index N typically ranging from -3 to -4. Polarimetric and light scattering studies suggest mixtures of porous agglomerates of sub-micrometer minerals with organic matter. Cometary dust particles have low tensile strength, and low density.
... Besides being almost non-destructive (only the uppermost molecular layer of a studied surface is affected), TOF-SIMS, with its latest technical developments, is one of the rare techniques able to give rich information on the chemical composition and structure of the meteorite organic content in-situ, i.e., within the chondrite mineral matrix and together with a characterization of the mineral contents. TOF-SIMS has previously been used for the analysis of extraterrestrial samples, such as interplanetary dust grains [44], cometary particles from the Stardust mission [45][46][47], as well as meteoritic fragments and tiny inclusions within meteorites [48][49][50][51]. However, previous TOF-SIMS studies of primitive extra-terrestrial matter essentially focused on elements' repartition in minerals (Si + , Mg + , Ca + , Fe + , S − etc.), and a few of them identified some PAHs in the organic phases [52]. ...
... Besides being almost non-destructive (only the uppermost molecular layer of a studied surface is affected), TOF-SIMS, with its latest technical developments, is one of the rare techniques able to give rich information on the chemical composition and structure of the meteorite organic content insitu, i.e. within the chondrite mineral matrix and together with a characterization of the mineral contents. TOF-SIMS has previously been used for the analysis of extraterrestrial samples, such as interplanetary dust grains [44], cometary particles from the Stardust mission [45][46][47], as well as meteoritic fragments and tiny inclusions within meteorites [48][49][50][51]. However, previous TOF-SIMS studies of primitive extra-terrestrial matter essentially focused on elements' repartition in minerals (Si + , Mg + , Ca + , Fe + , S − etc.), and a few of them identified some PAHs in the organic phases [52]. ...
This study is a multi-technique investigation of the Paris carbonaceous chondrite directly applied on two selected 500 × 500 µm² areas of a millimetric fragment, without any chemical extraction. By mapping the partial hydration of the amorphous silicate phase dominating the meteorite sample matrix, infrared spectroscopy gave an interesting glimpse into the way the fluid may have circulated into the sample and partially altered it. The TOF-SIMS in-situ analysis allowed the studying and mapping of the wide diversity of chemical moieties composing the meteorite organic content. The results of the combined techniques show that at the micron scale, the organic matter was always spatially associated with the fine-grained and partially-hydrated amorphous silicates and to the presence of iron in different chemical states. These systematic associations, illustrated in previous studies of other carbonaceous chondrites, were further supported by the identification by TOF-SIMS of cyanide and/or cyanate salts that could be direct remnants of precursor ices that accreted with dust during the parent body formation, and by the detection of different metal-containing large organic ions. Finally, the results obtained emphasized the importance of studying the specific interactions taking place between organic and mineral phases in the chondrite matrix, in order to investigate their role in the evolution story of primitive organic matter in meteorite parent bodies.
... Unfortunately, the relatively poor preservation of micrometer and smaller particles in aerogel ) makes them difficult to interpret. Although the major element composition of small areas on the walls of large aerogel tracks may resemble that of bulk chondritic meteorites Stephan et al. 2008), it is not yet proven whether these are remnants of sub-micrometer scale amorphous dust, or mixed impact residues from several different (possibly even crystalline) components, spattered and partly dissolved into high-temperature silica melt. The chemical composition of these fine patches is therefore not an unequivocal indicator of IS or DMC particle types (Zhukovska et al. 2008) as might be expected to be fractal grain cores in the model of Greenberg et al. (1989). ...
... However, evidence of progressive release of carbon monoxide within cometary comae (Cottin et al. 2004) perhaps reveals the presence of labile polymeric organic matter, which we suggest may have acted as a weak adhesive prior to gradual dissociation by ultra-violet irradiation, loss of vapor, creation of still further internal pore-space and unlocking of sub-grains. Some organic matter clearly survived to be collected by Stardust both in aerogel and on foils (e.g., Sandford et al. 2006;Stephan et al. 2008), and in their study of carbon and nitrogen in Wild 2 particles in aerogel, Gallien et al (2008) conclude that vaporization of surviving organic matter may even have contributed to the expansion of bulbous tracks. and Leitner et al. (2008) report carbonaceous remnants preserved around the edge of a very complicated crater, interpreted as a rare high porosity aggregate. ...
Abstract— New experimental results show that Stardust crater morphology is consistent with interpretation of many larger Wild 2 dust grains being aggregates, albeit most of low porosity and therefore relatively high density. The majority of large Stardust grains (i.e. those carrying most of the cometary dust mass) probably had density of 2.4 g cm−3 (similar to soda-lime glass used in earlier calibration experiments) or greater, and porosity of 25% or less, akin to consolidated carbonaceous chondrite meteorites, and much lower than the 80% suggested for fractal dust aggregates. Although better size calibration is required for interpretation of the very smallest impacting grains, we suggest that aggregates could have dense components dominated by μm-scale and smaller sub-grains. If porosity of the Wild 2 nucleus is high, with similar bulk density to other comets, much of the pore space may be at a scale of tens of micrometers, between coarser, denser grains.
Successful demonstration of aggregate projectile impacts in the laboratory now opens the possibility of experiments to further constrain the conditions for creation of bulbous (Type C) tracks in aerogel, which we have observed in recent shots. We are also using mixed mineral aggregates to document differential survival of pristine composition and crystalline structure in diverse finegrained components of aggregate cometary dust analogues, impacted onto both foil and aerogel under Stardust encounter conditions.
... The aerogel witness coupon material analyzed with TOF-SIMS showed a PAH spectrum similar to that observed in a dissected aerogel keystone containing an actual cometary particle track (Stephan et al. 2008). However, compared to the witness coupon, PAH concentrations are up to a factor of six higher in aerogel associated with the track (Stephan et al. 2008). ...
... The aerogel witness coupon material analyzed with TOF-SIMS showed a PAH spectrum similar to that observed in a dissected aerogel keystone containing an actual cometary particle track (Stephan et al. 2008). However, compared to the witness coupon, PAH concentrations are up to a factor of six higher in aerogel associated with the track (Stephan et al. 2008). Furthermore, this factor of six may be regarded as a lower limit since the Ar + sputter cleaning (see SOM) that was performed on the track sample (but not on the witness coupon material) to diminish surface contamination should also have diminished the PAHs in the sample associated with the track. ...
Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si-CH3 groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.
... One likely source of contamination on the aluminum foils is small fragments of the nearby aerogel. Since the Mg/Si ratio of Stardust aerogel is very low (Tsou et al. 2003; Stephan et al. 2008), we separate the Si-rich deposits and grains into two groups, one with relatively high Mg/Si, and a second with very low Mg/Si, potentially aerogel. Figure 9 shows the abundances of several elements relative to Si for six individual Mg-and Si-rich spots, of which three are displayed in Figs. ...
... Next to Si and Mg, the main constituents are C and O, while other elements contribute only very little to the composition. For comparison, elemental abundances for three aerogel blanks analyzed by Stephan et al. (2008) are displayed in Fig. 9. They show that for all elements abundances relative to Si in aerogel much lower than observed for the Al foil regions. ...
Abstract— Impact residues of cometary particles on aluminum foils from the Stardust mission were investigated with TOF-SIMS for their elemental and organic composition. The residual matter from comet 81P/Wild 2 shows a wide compositional range, from nearly monomineralic grains to polymict aggregates. Despite the comparably small analyzed sample volume, the average element composition of the investigated residues is similar to bulk CI chondritic values. Analysis of organic components in impact residues is complicated, due to fragmentation and alteration of the compounds during the impact process and by the presence of contaminants on the aluminum foils. Nevertheless, polycyclic aromatic hydrocarbons (PAHs) that are unambiguously associated with the impact residues were observed, and thus are most likely of cometary origin.
... In geologic samples, ToF-SIMS has been used to analyze oil-bearing fluid inclusions in hydrothermal fluorite and calcite veins (Siljeström et al., 2010), oil-bearing fluid inclusions within a Proterozoic sandstone (Siljeström et al., 2013), and crude oil and crude oil fractions (Sjövall et al., 2008;Siljeström et al., 2009) and on isolated kerogen (Sjövall et al., 2021). In planetary sciences, ToF-SIMS has been performed on meteorites (Stephan, 2001;Stephan et al., 2003;Noun et al., 2019), including martian meteorites containing organics (Steele et al., 2018), as well as on cometary particles (Stephan et al., 2008). ...
The ability to detect and map lipids, including potential lipid biomarkers, within a sedimentary matrix using mass spectrometry (MS) imaging may be critical to determine whether potential lipids detected in samples returned from Mars are indigenous to Mars or are contaminants. Here, we use gas chromatography-mass spectrometry (GC-MS) and time-of-flight-secondary ion mass spectrometry (ToF-SIMS) datasets collected from an organic-rich, thermally immature Jurassic geologic sample to constrain MS imaging analysis of indigenous lipid biomarkers in geologic samples. GC-MS data show that the extractable fractions are dominated by C27-C30 steranes and sterenes as well as isorenieratene derivatives. ToF-SIMS spectra from organic matter-rich laminae contain a strong, spatially restricted signal for ions m/z 370.3, m/z 372.3, and m/z 386.3, which we assign to C27 sterenes, cholestane (C27), and 4- or 24-methyl steranes (C28), respectively, as well as characteristic fragment ions of isorenieratene derivatives, including m/z 133.1, m/z 171.1, and m/z 237.1. We observed individual steroid spatial heterogeneity at the scale of 10's to 100's of microns. The fine-scale heterogeneity observed implies that indigenous lipid biomarkers concentrated within specific regions may be detectable via ToF-SIMS in samples with even low amounts of organic carbon, including in samples returned from Mars.
... The aerogel keystones surrounding the tracks were extracted from the aerogel blocks and directly used for the detailed analyses or individual particle extraction (Westphal et al. 2004). The time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis of the Stardust sample showed the presence of PAHs that could possibly be attributed to Comet 81P/Wild 2 (Stephan et al. 2008). ...
This paper presents a review of the space exploration for life signature search with a special focus on the fluorescence microscope we developed for the life signature search on Mars and in other sites. Considering where, what, and how to search for life signature is essential. Life signature search exploration can be performed on the Mars surface and underground, on Venus’ cloud, moon, asteroids, icy bodies (e.g., moons of Jupiter and Saturn), and so on. It is a useful strategy to consider the targeted characteristics that may be similar to those of terrestrial microorganisms, which are microorganisms with uniform spherical or rod structures with approximately 1 μm diameter surrounded by a membrane having a metabolic activity and mainly made of carbon-based molecules. These characteristics can be analyzed by using a fluorescence microscope and a combination of fluorescence pigments with specific staining characteristics to distinguish the microorganism characteristics. Section 1 introduces the space exploration for life signature search. Section 2 reviews the scientific instruments and achievements of past and ongoing Mars exploration missions closely related to astrobiology. Section 3 presents the search targets and analysis of astrobiology. Section 4 discusses the extraterrestrial life exploration methods that use a microscope together with other methods (based on mass spectrometry, morphology, detection of growth, movement, and death, etc. for microscopic and macroscopic organism). Section 5 expounds on the life signature detection fluorescence microscope, for which we have manufactured a bread board model and tested for extraterrestrial life exploration.
... The error stated refers to 95% confidence level for the statistical error, 30% assumed systematic error of TOF-SIMS calibration, and takes into account the uncertainty related to the relative sensitivity factors used for quantification (Krüger et al. 2015). For comparison, the Stardust results from comet 81P/Wild cometary particle analysis are shown (Ishii et al. 2008;Lanzirotti et al. 2008;Leroux et al. 2008;Stephan 2008;Stephan et al. 2008;Brownlee 2014). 256.28 u. ...
ABSTRACT
The COmetary Secondary Ion Mass Analyser instrument on board ESA!s Rosetta mission has collected dust
particles in the coma of comet 67P/Churyumov–Gerasimenko. During the early-orbit phase of the Rosetta mission,
particles and particle agglomerates have been imaged and analyzed in the inner coma at distances between 100 km
and 10 km off the cometary nucleus and at more than 3 AU from the Sun. We identi!ed 585 particles of more than
14 !m in size. The particles are collected at low impact speeds and constitute a sample of the dust particles in the
inner coma impacting and fragmenting on the targets. The sizes of the particles range from 14 !m up to submillimeter
sizes and the differential dust "ux size distribution is !tted with a power law exponent of −3.1. After
impact, the larger particles tend to stick together, spread out or consist of single or a group of clumps, and the
"occulent morphology of the fragmented particles is revealed. The elemental composition of the dust particles is
heterogeneous and the particles could contain typical silicates like olivine and pyroxenes, as well as iron sul!des.
The sodium to iron elemental ratio is enriched with regard to abundances in CI carbonaceous chondrites by a factor
from !1.5 to !15. No clear evidence for organic matter has been identi!ed. The composition and morphology of
the collected dust particles appear to be similar to that of interplanetary dust particles.
... The compositions of the grains are almost pure SiO 2, with minor Fe, Al, P, and K (»0.7, 0.5, 0.4, and 0.1 at.%, respectively), suggesting that the amorphous silica is a flash-melted cristobalite grain during the impact. Indeed, the presence of a small amount of cation substitution is frequent in natural cristobalite (Smith & Steele 1984), while the flight aerogel contain impurities at the ppm level (Lanzirotti et al. 2008;Stephan et al. 2008). Furthermore, no vesicles were observed, whereas molten aerogel always exhibits large vesicles (see Leroux et al. 2008b for details). ...
Crystalline silica (SiO2) is recurrently identified at the percent level in the infrared spectra of protoplanetary disks. By contrast, reports of crystalline silica in primitive meteorites are very unusual. This dichotomy illustrates the typical gap existing between astrophysical observations and meteoritical records of the first solids formed around young stars. The cometary samples returned by the Stardust mission in 2006 offer an opportunity to have a closer look at a silicate dust that experienced a very limited reprocessing since the accretion of the dust. Here, we provide the first extended study of silica materials in a large range of Stardust samples. We show that cristobalite is the dominant form. It was detected in 5 out of 25 samples. Crystalline silica is thus a common minor phase in Stardust samples. Furthermore, olivine is generally associated with this cristobalite, which put constraints on possible formation mechanisms. A low-temperature subsolidus solid-solid transformation of an amorphous precursor is most likely. This crystallization route favors the formation of olivine (at the expense of pyroxenes), and crystalline silica is the natural byproduct of this transformation. Conversely, direct condensation and partial melting are not expected to produce the observed mineral assemblages. Silica is preserved in cometary materials because they were less affected by thermal and aqueous alterations than their chondritic counterparts. The common occurrence of crystalline silica therefore makes the cometary material an important bridge between the IR-based mineralogy of distant protoplanetary disks and the mineralogy of the early solar system.
... The preflight, density-graded, underdense aerogel is not 100% pure silica, but contains mostly ppb-level impurities (Tsou et al. 2003). Initial studies of Stardust flight aerogel and glass found elevated aerogel contaminant levels (Lanzirotti et al. 2008; Stephan et al. 2008). It turns out that silica glass extracted from the walls of bulbous parts of type B tracks and the walls of type C tracks shows a distinct distribution pattern for the Fe-and CI-normalized abundances of Na, Mg, Al, S, Cl, K, Ca, Cr, Mn, Fe, and Ni that exactly matches this distribution pattern for these elements found in preflight aerogel (Rietmeijer 2009a). ...
We present the analyses results of two bulk Terminal Particles, C2112,7,171,0,0 and C2112,9,171,0,0, derived from the Jupiter-family comet 81P/Wild 2 returned by the Stardust mission. Each particle embedded in a slab of silica aerogel was pressed in a diamond cell. This preparation, as expected, made it difficult to identify the minerals and organic materials present in these particles. This problem was overcome using a combination of three different analytical techniques, viz. FE-SEM/EDS, IR, and Raman microspectroscopy that allowed identifying the minerals and small amounts of amorphous carbon present in both particles. TP2 and TP3 were dominated by Ca-free and low-Ca, Mg-rich, Mg,Fe-olivine. The presence of melilite in both particles is supported by IR microspectroscopy, but is not confirmed by Raman microspectroscopy, possibly because the amounts are too small to be detected. TP2 and TP3 show similar silicate mineral compositions, but Ni-free and low-Ni, subsulfur (Fe,Ni)S grains are present in TP2 only. TP2 contains indigenous amorphous carbon hot spots; no indigenous carbon was identified in TP3. These nonchondritic particles probably originated in a differentiated body. This work found an unanticipated carbon contamination following the FE-SEM/EDS analyses. It is suggested that organic materials in the embedding silica aerogel are irradiated during FE-SEM/EDS analyses creating a carbon gas that develops a strong fluorescence continuum. The combination of the selected analytical techniques can be used to characterize bulk Wild 2 particles without the need of extraction and removal of the encapsulating aerogel. This approach offers a relatively fast sample preparation procedure, but compressing the samples can cause spurious artifacts, viz. silica contamination. Because of the combination of techniques, we account for these artifacts.
... The particles struck the Stardust aerogel at ∼6.1 km s −1 . At this velocity, some of the impacting material was destroyed, some was altered and some survived unaltered [6,21,37,46,54]. This greatly complicates the interpretation of data obtained from samples extracted from the aerogel. ...
The Stardust mission returned cometary, interplanetary and (probably) interstellar dust in 2006 to Earth that have been analysed in Earth laboratories worldwide. Results of this mission have changed our view and knowledge on the early solar nebula. The Rosetta mission is on its way to land on comet 67P/Churyumov-Gerasimenko and will investigate for the first time in great detail the comet nucleus and its environment starting in 2014. Additional astronomy and planetary space missions will further contribute to our understanding of dust generation, evolution and destruction in interstellar and interplanetary space and provide constraints on solar system formation and processes that led to the origin of life on Earth. One of these missions, SARIM-PLUS, will provide a unique perspective by measuring interplanetary and interstellar dust with high accuracy and sensitivity in our inner solar system between 1 and 2 AU. SARIM-PLUS employs latest in-situ techniques for a full characterisation of individual micrometeoroids (flux, mass, charge, trajectory, composition) and collects and returns these samples to Earth for a detailed analysis. The opportunity to visit again the target comet of the Rosetta mission 67P/Churyumov-Gerasimeenternko, and to investigate its dusty environment six years after Rosetta with complementary methods is unique and strongly enhances and supports the scientific exploration of this target and the entire Rosetta mission. Launch opportunities are in 2020 with a backup window starting early 2026. The comet encounter occurs in September 2021 and the reentry takes place in early 2024. An encounter speed of 6 km/s ensures comparable results to the Stardust mission.
... Among others, Stephan et al. (2008) raised the possibility of a chemical background in flight aerogel perhaps inherited from the contaminants present in the preflight aerogel. The Si-rich glass with >40 Si el% is almost clear of visible electron-opaque Fe-Ni-S compound inclusions. ...
Abstract— Many of the nanometer-scale grains from comet 81P/Wild 2 did not survive hypervelocity capture. Instead, they melted and interacted with silica melt derived from the aerogel used by the Stardust mission. Their petrological properties were completely modified, but their bulk chemistry was preserved in the chemical signatures of mostly vesicular Si-rich glass with its typical Fe-Ni-S compound inclusions. Chondritic aggregate IDP L2011A9 that experienced atmospheric pre-entry thermal modification was selected as an analog to investigate these Wild 2 chemical signatures. The chemical, petrologic, and mineralogical properties of the individual constituents in this aggregate IDP are presented and used to match the chemical signatures of these Wild 2 grains. Mixing of comet material and pure silica, which is used in a diagram that recognizes this mixing behavior, is used to constrain the probable petrologic and minerals that caused the Wild 2 signatures. The Wild 2 nanometer-scale grain signatures in Si-rich glass allocations from three different deceleration tracks resembled mixtures of ultrafine-grained principal components and dense agglomerate-like material, Mg-rich silicates (<500 nm) and Fe,Ni-sulfides (<100 nm), and Si-rich amorphous material. Dust resembling the mixed matrix of common chondritic aggregate IDPs was present in Jupiter-family comet Wild 2.
... Some material is also present all along the track cavities but is found unfortunately largely melted. In this case the composition is frequently close to CI Stephan et al. 2008) and the deduced original grain size is more than one order smaller than the terminal particles. All these observations lead to conclude that dust particles which impacted the aerogel capture medium were weakly bound aggregates constituted by one or several large silicate grains together with a very fine grained matrix. ...
Abstract— We report the examination by transmission electron microscopy (TEM) of four Stardust terminal particles extracted from two neighboring tracks (32 an 69). The particles are made of well-preserved crystalline grains dominated by low-Ca pyroxene ranging from nearly pure enstatite to pigeonite. Some olivine grains are also found, in chemical equilibrium with the surrounding pyroxenes. Various microstructures are observed, as a function of the composition of the grains. They include (100)-twinned pigeonite, clino/ortho domains in enstatite and exsolution in a Ca-rich grain. The microstructures are mostly consistent with a formation by cooling from high-temperature phases, which could be associated to igneous processes. Some dislocations in glide configuration are also present, probably attesting for small intensity shocks. Possible effects of the rapid heating/cooling stage and thermal shock associated to the collect are discussed. It appears that most of the microstructural features reported here are plausibly pristine.
... For the analysis of the chemical composition of captured dust grains, further methods like scanning electron microscopes with energy dispersive spectrometers (SEM-EDS) and SXRF (synchrotron X-ray fluorescence) are available. A SEM-EDS technique was used to investigate the residues of Stardust samples that were captured on Al foil [40, 41], and TOF-SIMS results of isolated particle tracks in aerogel of collected dust were published in [56,656667. Here, most electron beam techniques so far failed due to intense charging of the aerogel. ...
The scientific community has expressed strong interest to re-fly Stardust-like missions with improved instrumentation. We propose a new mission concept, SARIM, that collects interstellar and interplanetary dust particles and returns them to Earth. SARIM is optimised for the collection and discrimination of interstellar dust grains. Improved active dust collectors on-board allow us to perform in-situ determination of individual dust impacts and their impact location. This will provide important constraints for subsequent laboratory analysis.
The SARIM spacecraft will be placed at the L2 libration point of the Sun–Earth system, outside the Earth’s debris belts and inside the solar-wind charging environment. SARIM is three-axes stabilised and collects interstellar grains between July and October when the relative encounter speeds with interstellar dust grains are lowest (4 to 20 km/s). During a 3-year dust collection period several hundred interstellar and several thousand interplanetary grains will be collected by a total sensitive area of 1 m2. At the end of the collection phase seven collector modules are stored and sealed in a MIRKA-type sample return capsule. SARIM will return the capsule containing the stardust to Earth to allow for an extraction and investigation of interstellar samples by latest laboratory technologies.
... Sulfur is found as S-rich rims on opaque inclusions and rare " sulfur hot spots. " Time-of-flight secondary ion mass spectrometry (ToF-SIMS) data for cometary material in C2115,30,21,0 and C2115,34,21,0 show close to Fe-and CI-normalized abundances—for Mg, Al, Cr, and Mn close to the CI abundances, Ca is much lower than CI, and above CI Ni abundances (Stephan et al. 2008). The high Ni abundances are within the range shown inFig. ...
We report the results of high-resolution, analytical and scanning transmission electron microscopy (STEM), including intensive element mapping, of severely thermally modified dust from comet 81P/Wild 2 caught in the silica aerogel capture cells of the Stardust mission. Thermal interactions during capture caused widespread melting of cometary silicates, Fe-Ni-S phases, and the aerogel. The characteristic assemblage of thermally modified material consists of a vesicular, silica-rich glass matrix with abundant Fe-Ni-S droplets, the latter of which exhibit a distinct core-mantle structure with a metallic Fe,Ni core and a iron-sulfide rim. Within the glassy matrix, the elemental distribution is highly heterogeneous. Localized amorphous "dust-rich" patches contain Mg, Al, and Ca in higher abundances and suggest incomplete mixing of silicate progenitors with molten aerogel. In some cases, the element distribution within these patches seems to depict the outlines of ghost mineral assemblages, allowing the reconstruction of the original mineralogy. A few crystalline silicates survived with alteration limited to the grain rims. The Fe- and CI-normalized bulk composition derived from several sections show CI-chondrite relative abundances for Mg, Al, S, Ca, Cr, Mn, Fe, and Ni. The data indicate a 5 to 15% admixture of fine-grained chondritic comet dust with the silica glass matrix. These strongly thermally modified samples could have originated from a finegrained primitive material, loosely bound Wild 2 dust aggregates, which were heated and melted more efficiently than the relatively coarse-grained material of the crystalline particles found elsewhere in many of the same Stardust aerogel tracks (Zolensky et al. 2006).
In this review, we discuss the use of time–of–flight secondary–ion mass spectrometry (TOF–SIMS) technology for analyzing the viscous glue (is called aggregate glue droplets) of spider orb webs and examine the results obtained. Element distribution images of the aggregate glue droplets were observed by TOF–SIMS. A uniform element distribution is seen for suspended pristine aggregate glue droplets, and a differential spreading of aggregate glue components is seen for attached aggregate glue droplets. We also observed TOF–SIMS images of water in aggregate glue droplets, where water was observed to be consistent with the distribution of oozing salt. We also found that the alkali metal in the aggregate glue droplets showed similar characteristics by feeding cesium carbonate to spiders.
Two-color resonant laser ionization sputtered neutral mass spectrometry offers high elemental selectivity. In this study, two-color resonance ionization in sputtered neutral Sr was confirmed by combining a grating type Ti:sapphire laser system and a time-of-flight secondary ion mass spectrometry (TOF-SIMS) system. The authors compared the ionization efficiencies of Sr of the two-color three-photon ionization scheme 1 (first step: 460.862 nm; second step: 767.519 nm) and the two-color two-photon ionization scheme 2 (first step: 460.862 nm; second step: 405.200 nm). The resonant ionization efficiency of the latter was found to be 50 times larger than that of the former. Finally, the authors mapped the microarea distribution of Sr by two-color resonant ionization sputtered neutral mass spectrometry.
The Cometary Secondary Ion Mass Analyzer (COSIMA) onboard ESA's Rosetta orbiter has revealed that dust particles in the coma of Comet 67P/Churyumov-Gerasimenko are aggregates of small grains. We study the morphological, elastic, and electric properties of dust aggregates in the coma of Comet 67P/Churyumov-Gerasimenko using optical microscopic images taken by the COSIMA instrument. Dust aggregates in COSIMA images are well represented as fractals in harmony with morphological data from MIDAS (Micro-Imaging Dust Analysis System) and GIADA (Grain Impact Analyzer and Dust Accumulator) onboard Rosetta. COSIMA's images, together with the data from the other Rosetta's instruments such as MIDAS and GIADA do not contradict the so-called rainout growth of $10~\mu\mathrm{m}$-sized particles in the solar nebula. The elastic and electric properties of dust aggregates measured by COSIMA suggest that the surface chemistry of cometary dust is well represented as carbonaceous matter rather than silicates or ices, consistent with the mass spectra, and that organic matter is to some extent carbonized by solar radiation, as inferred from optical and infrared observations of various comets. Electrostatic lofting of cometary dust by intense electric fields at the terminator of its parent comet is unlikely, unless the surface chemistry of the dust changes from a dielectric to a conductor. Our findings are not in conflict with our current understanding of comet formation and evolution, which begin with the accumulation of condensates in the solar nebula and follow with the formation of a dust mantle in the inner solar system.
The Cometary Secondary Ion Mass Analyzer (COSIMA) onboard ESA’s Rosetta orbiter has revealed that dust particles in the coma of comet 67P/Churyumov-Gerasimenko are aggregates of small grains. We study the morphological, elastic, and electric properties of dust aggregates in the coma of comet 67P/Churyumov-Gerasimenko using optical microscopic images taken by the COSIMA instrument. Dust aggregates in COSIMA images are well represented as fractals in harmony with morphological data from MIDAS (Micro-Imaging Dust Analysis System) and GIADA (Grain Impact Analyzer and Dust Accumulator) onboard Rosetta. COSIMA’s images, together with the data from the other Rosetta’s instruments such as MIDAS and GIADA do not contradict the so-called rainout growth of 10 μm-sized particles in the solar nebula. The elastic and electric properties of dust aggregates measured by COSIMA suggest that the surface chemistry of cometary dust is well represented as carbonaceous matter rather than silicates or ices, consistent with the mass spectra, and that organic matter is to some extent carbonized by solar radiation, as inferred from optical and infrared observations of various comets. Electrostatic lofting of cometary dust by intense electric fields at the terminator of its parent comet is unlikely, unless the surface chemistry of the dust changes from a dielectric to a conductor. Our findings are not in conflict with our current understanding of comet formation and evolution, which begin with the accumulation of condensates in the solar nebula and follow with the formation of a dust mantle in the inner solar system.
Based on a review of recent domestic and international literature, examples of using secondary ion mass spectrometry (SIMS) for the determination of carbon and hydrogen in solving particular problems of geochemistry and space chemistry are presented. Special attention is paid to problems arising in calibration procedures for the quantitative determination of carbon and hydrogen by SIMS. A summary of equipment currently used for SIMS analysis is given. Mass spectral imaging method based on mathematical processing of the recorded secondary ion currents of carbon and hydrogen for visualizing 3D distributions of elements is considered in detail.
Solar System formation models predict that the building-blocks of planetesimals were mm- to cm-sized pebbles, aggregates of ices and non-volatile materials, consistent with the compact particles ejected by comet 67P/Churyumov-Gerasimenko (67P hereafter) and detected by GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the Rosetta spacecraft. Planetesimals were formed by the gentle gravitational accretion of pebbles, so that they have an internal macroporosity of 40%. We measure the average dust bulk density $\rho _D = 795_{-65}^{+840}$ kg m⁻³ that, coupled to the 67P nucleus bulk density, provides the average dust-to-ices mass ratio δ = 8.5. We find that the measured densities of the 67P pebbles are consistent with a mixture of (15 ± 6)% of ices, (5 ± 2)% of Fe-sulfides, (28 ± 5)% of silicates, and (52 ± 12)% of hydrocarbons, in average volume abundances. This composition matches both the solar and CI-chondritic chemical abundances, thus showing that GIADA has sampled the typical non-volatile composition of the pebbles that formed all planetesimals. The GIADA data do not constrain the abundance of amorphous silicates vs. crystalline Mg,Fe-olivines and pyroxenes. We find that the pebbles have a microporosity of (52 ± 8)% (internal volume filling factor ϕP = 0.48 ± 0.08), implying an average porosity for the 67P nucleus of (71 ± 8)%, lower than previously estimated.
Bulk compositions of aggregate meteoroids made of the originally accreted dust with its highly varied in mineral content and chemistry and considerable grain size variations do not have a chondritic bulk composition. Deviations from CI element abundances reflect indigenous variations within and among comet nuclei. These unmodified meteoroids that are heterogeneous in all their properties are fundamentally different from meteoroids with a CI bulk composition that are fine-grained, equigranular materials and chemically and mineralogically homogeneous. Collection and data reduction bias exists but the compositions of individual fast meteors are entirely constrained by the measured main component meteor abundances.
In 2006, NASA's Stardust spacecraft delivered to Earth dust particles collected from the coma of comet 81P/Wild 2, with the goal of furthering the understanding of solar system formation. Stardust cometary samples were collected in a low-density, nanoporous silica aerogel making their study technically challenging. This article demonstrates the identification, exposure, and elemental composition analysis of particles analogous to those collected by NASA's Stardust mission using in-situ SEM techniques. Backscattered electron imaging is shown by experimental observation and Monte Carlo simulation to be suitable for locating particles of a range of sizes relevant to Stardust (down to submicron diameters) embedded within silica aerogel. Selective removal of the silica aerogel encapsulating an embedded particle is performed by cryogenic NF3-mediated electron beam-induced etching. The porous, low-density nature of the aerogel results in an enhanced etch rate compared with solid material, making it an effective, nonmechanical method for the exposure of particles. After exposure, elemental composition of the particle was analyzed by energy-dispersive X-ray spectroscopy using a high spectral resolution microcalorimeter. Signals from fluorine contamination are shown to correspond to nonremoved silica aerogel and only in residual concentrations.
In Stardust tracks C2044,0,38, C2044,0,39, and C2044,0,42 (Brennan et al. 2007) and Stardust track 10 (this work) gold is present in excess of its cosmochemical abundance. Ultra-thin sections of allocation FC6,0,10,0,26 (track 10) show a somewhat wavy, compressed silica aerogel/silica glass interface which challenges exact location identification, i.e., silica glass, compressed silica aerogel, or areas of overlap. In addition to domains of pure silica ranging from SiO2 to SiO3 glass, there is MgO-rich silica glass with a deep metastable composition, MgO = 14 ± 6 wt%, due to assimilation of Wild 2 Mg-silicate matter in silica melt. This magnesiosilica composition formed when temperatures during hypervelocity capture reached >2000 °C followed by ultrafast quenching of the magnesiosilica melt when it came into contact with compressed aerogel at ~155 °C. The compressed silica aerogel in track 10 has a continuous Au background as result of the melting point depression of gold particles <5 nm that showed liquid-like behavior. Larger gold particles are scattered found throughout the silica aerogel matrix and in aggregates up to ~50 nm in size. No gold is found in MgO-rich silica glass. Gold in track 10 is present at the silica aerogel/silica glass interface. In the other tracks gold was likely near-surface contamination possibly from an autoclave used in processing of these particular aerogel tiles. So far gold contamination is documented in these four different tracks. Whether they are the only tiles with gold present in excess of its cosmochemical abundance or whether more tiles will show excess gold abundances is unknown.
This chapter focuses on time-of-flight secondary ion mass spectrometry (TOF-SIMS), where the ion beam is pulsed, and extensions that involve postionization of sputtered neutrals. It introduces the basic principles of TOF-SIMS and discusses recent applications in inorganic chemistry. Variations of the technique that make it useful for organic analysis are described and recent applications reviewed. Developments of the technique, in particular those employing laser postionization (resonant and nonresonant) of sputtered neutrals, are described and recent results discussed, including resonance ionization mass spectrometry of noble gases.
The bulbous Stardust track #80 (C2092,3,80,0,0) is a huge cavity. Allocations C2092,2,80,46,1 nearest the entry hole and C2092,2,80,47,6 about 0.8 mm beneath the entry hole provide evidence of highly chaotic conditions during capture. They are dominated by nonvesicular low-Mg silica glass instead of highly vesicular glass found deeper into this track which is consistent with the escape of magnesiosilica vapors generated from the smallest comet grains. The survival of delicate (Mg,Al,Ca)-bearing silica glass structures is unique to the entry hole. Both allocations show a dearth of surviving comet dust except for a small enstatite, a low-Ca hypersthene grain, and a Ti-oxide fragment. Finding scattered TiO2 fragments in the silica glass could support, but not prove, TiO2 grain fragmentation during hypervelocity capture. The here reported dearth in mineral species is in marked contrast to the wealth of surviving silicate and oxide minerals deeper into the bulb. Both allocations show Fe-Ni-S nanograins dispersed throughout the low-Mg silica glass matrix. It is noted that neither comet Halley nor Wild 2 had a CI bulk composition for the smallest grains. Using the analogs of interplanetary dust particles (IDPs) and cluster IDPs it is argued that a CI chondritic composition requires the mixing of nonchondritic components in the appropriate proportions. So far, the fine-grained Wild 2 dust is biased toward nonchondritic ferromagnesiosilica materials and lacking contributions of nonchondritic components with Mg-Fe-Ni-S[Si-O] compositions. To be specific, “Where are the GEMS”? The GEMS look-alike found in this study suggests that evidence of GEMS in comet Wild 2 may still be found in the Stardust glass.
Comet samples returned to Earth by the NASA Stardust mission have provided a surprising glimpse into the nature of early Solar System materials and an epiphany on the origin of the initial rocky materials that once filled the cold regions of the solar nebula. The findings show that the cold regions of the early Solar System were not isolated and were not a refuge where interstellar materials could commonly survive. Wild 2, the sampled comet, appears to be a typical active Jupiter family comet, and yet most of its sampled micron and larger grains are familiar high-temperature meteoritic materials, such as chondrule fragments, that were transported to cold nebular regions. The rocky components in primitive asteroids and comets may differ because asteroid formation was dominated by local materials, whereas comets formed from mixed materials, many of which were transported from very distant locations.
The oxidation state of transition metal elements is an indicator of the
environmental conditions during formation and history of
extraterrestrial materials. We studied the iron valence state of
fine-grained material from a bulbous track extracted from the Stardust
cometary collector. It likely originated from primitive material of the
comet Wild 2. We used synchrotron-based Scanning Transmission X-ray
Microscopy (STXM) to collect Fe L3-XANES spectra at a spatial
resolution of about 20 nm. Maps of Fe valence state were combined with
the elemental maps recorded by energy dispersive X-ray spectroscopy
(EDS) with a transmission electron microscope (TEM), on the same areas
and with a comparable electron probe size (5–20 nm). As for most
Stardust fine-grained material, the samples are severely damaged by the
hypervelocity impact in the aerogel collector blocks. They show of a
wide range of oxidation state at a micrometer scale, from Fe metal to
Fe3+. This heterogeneity of oxidation state can be due to the
extreme conditions of the collection. Two major parameters can favor
changes in redox state. The first is the high temperature regime, known
to be highly heterogeneous and to have locally reached extreme values
(up to 2000 K). The second is the local chemical environment. It may
contain elements that could favor a reduction or oxidation reaction
within the flash-heated Wild 2 fragments. Comparison of maps by STXM and
EDS shows evidence for several correlation trends between element
concentrations and the iron valence state. These observations, together
with the study of a melted rim of a larger particle, suggest that the
redox state was not completely redistributed within the impact melts.
These local signatures are compatible with precursors that could have
been close to primitive matrix material of chondrites or to chondritic
interplanetary dust particles. On average, the fine-grained material
from Wild 2 displays a molar fraction (Fe2+oxide +
Fe3+oxide)/(total Fe) equal to 0.80 ± 0.10.
It appears more oxidized than the average value measured for the comet,
when done on larger particles (Westphal et al., 2009). This fine-grained
material from Wild 2 does not seem to have sampled reducing environments
in the solar nebulae in contrast with the larger particles of Wild 2.
This observation confirms the high degree of diversity of materials in
Wild 2 and is in good agreement with the dual distribution of high
temperature minerals and matrices in carbonaceous chondrites.
We report the presence of preserved primitive fine-grained material containing an enstatite whisker with the crystallographic characteristics of a primary condensate in a sample of the Jupiter-family comet Wild 2, returned to earth by NASAʼs Stardust mission. The preserved primitive material is composed of silica-rich amorphous material embedded with iron sulfides and silicates. It is in close association with a type II chondrule-like object in the track C2052,2,74 (Ogliore et al., 2012). The close association of a chondrule and a primary condensate shows they must have formed in different environments and probably met in the comet-forming region. The first observation of an enstatite whisker with properties indicating primary condensation in a comet is a new link between comets and Chondritic Porous IDPs (CP-IDPs).
The grains returned by NASA's Stardust mission from comet 81P/Wild 2
represent a valuable sample set that is significantly advancing our
understanding of small solar system bodies. However, the grains were
captured via impact at ˜6.1 km s-1 and have experienced
pressures and temperatures that caused alteration. To ensure correct
interpretations of comet 81P/Wild 2 mineralogy, and therefore
preaccretional or parent body processes, an understanding of the effects
of capture is required. Using a two-stage light-gas gun, we recreated
Stardust encounter conditions and generated a series of impact analogs
for a range of minerals of cometary relevance into flight spare Al
foils. Through analyses of both preimpact projectiles and postimpact
analogs by transmission electron microscopy, we explore the impact
processes occurring during capture and distinguish between those
materials inherent to the impactor and those that are the product of
capture. We review existing and present additional data on olivine,
diopside, pyrrhotite, and pentlandite. We find that surviving
crystalline material is observed in most single grain impactor residues.
However, none is found in that of a relatively monodisperse aggregate. A
variety of impact-generated components are observed in all samples. Al
incorporation into melt-derived phases allows differentiation between
melt and shock-induced phases. In single grain impactor residues,
impact-generated phases largely retain original (nonvolatile) major
element ratios. We conclude that both surviving and impact-generated
phases in residues of single grain impactors provide valuable
information regarding the mineralogy of the impacting grain whilst
further studies are required to fully understand aggregate impacts and
the role of subgrain interactions during impact.
The deceleration tracks in the Stardust aerogel display a wide range of
morphologies, which reveal a large diversity of incoming particles from
comet 81P/Wild 2. If the large and dense mineral grains survived the
extreme conditions of hypervelocity capture, this was not the case for
the fine-grained material that is found strongly damaged within the
aerogel. Due to their low mechanical strength, these assemblages were
disaggregated, dispersed, and flash melted in the aerogel in walls of
bulbous deceleration tracks. Their petrologic and mineralogical
properties are found significantly modified by the flash heating of the
capture. Originating from a quenched melt mixture of comet material and
aerogel, the representative microstructure consists of silica-rich
glassy clumps containing Fe-Ni-S inclusions, vesicles and "dust-rich"
patches, the latter being remnants of individual silicate components of
the impacting aggregate. The average composition of these melted
particle fragments is close to the chondritic CI composition. They might
originate from ultrafine-grained primitive components comparable to
those found in chondritic porous IDPs. Capture effects in aerogel and
associated sample biases are discussed in terms of size, chemical and
mineralogical properties of the grains. These properties are essential
for the grain survival in the extremely hot environment of hypervelocity
impact capture in aerogel, and thus for inferring the correct properties
of Wild 2 material.
Secondary Ion Mass Spectrometry (SIMS) enables surface chemical analysis of nano-scaled objects and chemical imaging of nano-scaled details of natural or artificial objects. This review presents the state of the art in nanoscale SIMS analysis. At first a short introduction into recent instrumentation for high resolution SIMS imaging and the limiting factors of lateral resolution is given. The next section covers the chemical analysis of nanoparticles. Recent applications of nanoscale imaging SIMS in geology, cosmochemistry, materials research, cellular biology, ecology and medical research are summarized and illustrated by examples.
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a technique designed to analyze the composition and spatial distribution of molecules and chemical structures on surfaces. These capabilities have generated much interest in its use in geobiology, in particular for the characterization of organic biomarkers (molecular biosignatures) at the microscopic level. We here discuss the strengths, weaknesses, and potential of ToF-SIMS for biomarker analyses with a focus on applications in geobiology, including biogeochemistry, organic geochemistry, geomicrobiology, and paleobiology. After describing the analytical principles of ToF-SIMS, we discuss issues of biomarker spectral formation and interpretation. Then, key applications of ToF-SIMS to soft (microbial matter, cells), hard (microbial mineral precipitates), and liquid (petroleum) samples relevant in geobiology are reviewed. Finally, we examine the potential of ToF-SIMS in biomarker research and the current limitations and obstacles for which furthe...
Abstract– We have experimentally produced nanophase sulfide compounds and magnetite embedded in Si-rich amorphous materials by flash-cooling of a gas stream. Similar assemblages are ubiquitous, and often dominant components of samples of impact-processed silica aerogel tiles and submicron grains from comet 81P/Wild 2 were retrieved by NASA’s Stardust mission. Although the texture and compositions of nanosulfide compounds have been reproduced experimentally, the mechanisms of formation of these minerals and their relationship with the surrounding amorphous materials have not been established. In this study, we present evidence that both of these materials may not only be produced through cooling of a superheated liquid but they may have also been formed simultaneously by flash-cooling and subsequent deposition of a gas dominated by Fe-S-SiO-O2. In a dust generator at the Goddard Space Flight Center, samples are produced by direct gas-phase condensation from gaseous precursors followed by deposition, which effectively isolates the effects of gas-phase reactions from the effects of melting and condensation. High-resolution transmission electron microscopy images and energy-dispersive spectroscopy analysis show that these experiments replicate key features of materials from type B and type C Stardust tracks, including textures, distribution of inclusions, nanophase size, and compositional diversity. We argue that gas-phase reactions may have played a significant role in the capture environment for nanophase materials. Our results are consistent with a potential progenitor assemblage of micron and submicron-sized sulfides and submicron silica-bearing phases, which are commonly observed in chondritic interplanetary dust particles and in the matrices of the most pristine chondritic meteorites.
Abstract— In January 2006, the Stardust mission successfully returned dust samples from the tail of comet 81P/Wild 2 in two principal collection media, low-density silica aerogel and Al foil. While hypervelocity impacts at the Stardust encounter velocity of 6.1 km/s into Al foils are generally highly disruptive for natural, silicate-dominated impactors, previous studies have shown that many craters retain sufficient residue to allow a determination of the elemental and isotopic compositions of the original projectile. We have used two NanoSIMS ion microprobes to perform C, N, and O isotope imaging measurements on four large (59–295 μm in diameter) and on 47 small (0.32–1.9 μm in diameter) Al-foil impact craters as part of the Stardust preliminary examination (PE). Most analyzed residues in and around these craters are isotopically normal (solar) in their C, N, and O isotopic compositions. However, the debris in one large crater shows an average 15N enrichment of ˜450‰, which is similar to the bulk composition of some isotopically primitive interplanetary dust particles (IDPs) and to components of some primitive meteorites. A 250 nm grain in another large crater has an 17O enrichment with ˜2.65 times the solar 17O/16O ratio. Such an O isotopic composition is typical for circumstellar oxide or silicate grains from red giant or asymptotic giant branch stars. The discovery of this circumstellar grain clearly establishes that there is authentic stardust in the cometary samples returned by the Stardust mission. However, the low apparent abundance of circumstellar grains in Wild 2 samples and the preponderance of isotopically normal material indicates that the cometary matter is a diverse assemblage of presolar and solar system materials.
One of the prime objectives in the analysis of cometary dust collected by the Stardust space mission is to determine the elemental
composition of comet 81P/Wild 2. For this analysis, samples captured by two sampling media, silica aerogel and Al foil, were
available. While aerogel was qualified to sample the dust almost intact, particles impinging on Al foils produced hypervelocity
impact craters with residual cometary matter. Both sample types delivered valuable information on the cometary inventory,
even though a slight loss of volatiles was observed for impact residues on Al foils. Altogether an elemental composition close
to solar elemental abundances was observed, indicating that the early solar system was chemically rather homogeneous from
the innermost regions close to the sun to the outer edge of the solar system, the presumed region of cometary origin.
Bulk compositions of aggregate meteoroids made of the originally accreted dust with its highly varied in mineral content and
chemistry and considerable grain size variations do not have a chondritic bulk composition. Deviations from CI element abundances
reflect indigenous variations within and among comet nuclei. These unmodified meteoroids that are heterogeneous in all their
properties are fundamentally different from meteoroids with a CI bulk composition that are fine-grained, equigranular materials
and chemically and mineralogically homogeneous. Collection and data reduction bias exists but the compositions of individual
fast meteors are entirely constrained by the measured main component meteor abundances.
The NASA Stardust mission has provided for laboratory study an extensive data set of cometary dust of known provenance (from comet 81P/Wild 2) yielding detailed insights into the composition of the comet. Combined with the results of data from other missions to short-period Jupiter family comets (JFC), this has greatly deepened the understanding of such objects. If depressions on the surface of comet 81P/Wild 2 are all taken as evidence of impact cratering, their number suggests a long occupancy in the outer region of the Solar System. The dust from comet 81P/Wild 2 has been shown to be heavily deficient in pre-Solar grains and rich in materials formed at high temperatures in the inner Solar System. Although it is too early to know if this is typical of JFC, it does argue for rapid and thorough mixing of materials in the disk on timescales related to comet formation, and may also suggest outward migration of small icy bodies after their formation. Thus, instead of providing mainly new knowledge of the pre-Solar materials expected to be rich in comets, Stardust and comet 81P/Wild 2 have instead focussed attention on large-scale transport processes during the critical period when cometary parent bodies were forming in the early Solar System.
The nature of cometary organics is of great interest, both because these materials are thought to represent a reservoir of the original carbon-containing materials from which everything else in our solar system was made and because these materials may have played key roles in the origin of life on Earth. Because these organic materials are the products of a series of universal chemical processes expected to operate in the interstellar media and star-formation regions of all galaxies, the nature of cometary organics also provides information on the composition of organics in other planetary systems and, by extension, provides insights into the possible abundance of life elsewhere in the universe. Our current understanding of cometary organics represents a synthesis of information from telescopic and spacecraft observations of individual comets, the study of meteoritic materials, laboratory simulations, and, now, the study of samples collected directly from a comet, Comet P81/Wild 2.
The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.
We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed ( approximately 180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition.
Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class
of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics.
Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary
dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar
heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained,
a diverse suite of organic compounds is present and identifiable within the returned samples.
Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.
The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study.
The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment
of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are
much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to
have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system
included mixing on the grandest scales.
Tracks from ~0.5 µm particles, shot at ~20 km/s into aerogel to simulate Stardust's interstellar dust collection, were analyzed with TOF-SIMS. Particle residues distributed heterogeneously along the tracks can be localized and identified by TOF-SIMS.
Stardust, launched in 1999, is the first mission designed to bring samples from a known, recently deflected comet, 81P/Wild 2, on 2 January 2004 and is also the first to capture newly discovered contemporary interstellar dust streaming through our solar system. The Stardust aerogel collector accomplishes Stardust's primary science and will be returned to Earth with its captured samples on 15 January 2006 in a reentry capsule. Wild 2 samples will be captured at 6.12 km/s and represent well-preserved relics of the outer regions of our solar nebula and fundamental building blocks of our planetary system. Interstellar grains captured at velocities of less than 10 km/s are expected to survive intact and represent the main repositories of condensable elements that permeate the galaxy. These solid cometary and interstellar samples will be captured in two back-to-back sample collection trays filled with variable-density aerogel. There are 132 silica aerogel capture cells of 3 cm and 1 cm thickness for the cometary and the interstellar sides, respectively. The aerogel capture cells were wedged into the sample collection trays and wrapped on all four sides with 100-μm-thick pure aluminum foil to facilitate aerogel cell removal. The total exposed Wild 2 surface area is 1039 cm2 of aerogel and 153 cm2 of aluminum foil. Results from a preliminary examination for the Wild 2 samples will be reported within 9 months of sample return and for the interstellar samples a year later. After preliminary examination the samples will be transferred to the NASA Office of the Curator and made available to the general science community.
We compiled a table of all major, minor, and trace-element abundances in
89 interplanetary dust particles (IDPs) that includes data obtained with
proton-induced x-ray emission (PIXE), synchroton x-ray fluorescence
(SXRF), and secondary ion mass spectrometry (SIMS). For the first time,
the reliability of the trace-element abundances in IDPs is tested by
various crosschecks. We also report on the results of cluster analyses
that we performed on IDP compositions. Because of the incompleteness of
the data set, we included only the elements Cr, Mn, Ni, Cu, and Zn,
normalized to Fe and CI chondrite abundances, that are determined in 73
IDPs. The data arrange themselves in four rather poorly defined groups
that we discuss in relation to CI chondrites following the assumption
that on the average CI abundances are most probable. The largest group
(chondritic), with 44 members, has close to CI abundances for many
refractory and moderately refractory elements (Na, Al, Si, P, K, Sc, Ti,
V, Cr, Co, Ge, Sr). It is slightly depleted in Fe and more in Ca and S,
while the volatile elements (Cl, Cu, Zn, Ga, Se, Rb) are enriched by
=1.7 × CI and Br by 21 × CI. The low-Zn group, with 12
members, is very similar to the chondritic group except for its
Zn-depletion, stronger Ca-depletion and Fe-enrichment. The low-Ni group,
with 11 members, has Ni/Fe = 0.03 × CI and almost CI-like Ca, but
its extraterrestrial origin is not established. The last group (6
members) contains non-systematic particles of unknown origin. We found
that Fe is inhomogeneously distributed on a micron scale. Furthermore,
the abundances of elements that are measured near their limits of
detection are easily overestimated. These biases involved, the
incomplete data set and possible contaminating processes prevent us from
obtaining information on the specific origin(s) of IDPs from elemental
abundances.
Powdered Allende projectiles were fired into silica aerogel at 6.1 km/sec in order to evaluate particle retrieval and analysis techniques for samples from the Stardust mission. Since particles may disintegrate and ablate along the penetration paths in a high-porosity aerogel, TOF-SIMS analysis may be a suitable method to determine the distribution of such materials along the tracks as well as potential compositional modifications. Therefore, two ~350 µm-sized tracks, residing at the surface of a keystone specimen that was flattened between two silicon chips, were analyzed. TOF-SIMS allows for a detailed study of the chemical composition of particles that survived the impact mostly intact and of fine-grained material from disintegrated projectiles. In the investigated keystone, material from light gas gun debris dominated. Besides the two tracks, a continuous, 40-µm-thick surface layer of implanted material—probably gun residue—was found. One of the two analyzed tracks is compositionally distinct from this surface layer and is likely to contain residual material of an Allende projectile. The analyses clearly demonstrate that tracks, resulting from impactors in the 5–10 µm size range, can be successfully analyzed with TOF-SIMS.
— Infrared spectroscopy maps of some tracks made by cometary dust from 81P/Wild 2 impacting Stardust aerogel reveal an interesting distribution of organic material. Out of six examined tracks, three show presence of volatile organic components possibly injected into the aerogel during particle impacts. When particle tracks contained volatile organic material, they were found to be -CH2-rich, while the aerogel is dominated by the -CH3-rich contaminant. It is clear that the population of cometary particles impacting the Stardust aerogel collectors also includes grains that contained little or none of this organic component. This observation is consistent with the highly heterogeneous nature of collected grains, as seen by a multitude of other analytical techniques.
Abstract— Impact residues of cometary particles on aluminum foils from the Stardust mission were investigated with TOF-SIMS for their elemental and organic composition. The residual matter from comet 81P/Wild 2 shows a wide compositional range, from nearly monomineralic grains to polymict aggregates. Despite the comparably small analyzed sample volume, the average element composition of the investigated residues is similar to bulk CI chondritic values. Analysis of organic components in impact residues is complicated, due to fragmentation and alteration of the compounds during the impact process and by the presence of contaminants on the aluminum foils. Nevertheless, polycyclic aromatic hydrocarbons (PAHs) that are unambiguously associated with the impact residues were observed, and thus are most likely of cometary origin.
New abundance tables have been compiled for Cl chondrites and the solar photosphere and corona, based on a critical review of the literature to mid-1988. The meteorite data are generally accurate to ± 5–10%. Significant discrepancies between Sun and meteorites occur only for Fe, Mn, Ge, Pb, and W; other well-determined elements agree to ±9% on the average. There is no evidence for group fractionations in Cl chondrites of cosmochemically similar elements (refractories, siderophiles, volatiles, etc.), but a selective fractionation of Fe cannot be ruled out. Abundances of odd-A nuclides between A = 65 and 209 show a generally smooth trend, with elemental abundances conforming to the slope defined by isotopic abundances. Significant irregularities occur in the NdSmEu region, however, suggesting that the abundance curve is dependably smooth only down to the ∼20% level.
Stardust, the 4th Discovery mission launched in February 1999, will collect coma samples from the recently deflected comet 81P/Wild 2 on 2 January 2004 and return them to Earth on 15 January 2006 for detailed laboratory analyses. Stardust will be the first mission to bring samples back to Earth from a known comet and also the first to bring back contemporary interstellar particles recently discovered. These samples should provide important insights into the nature and amount of dust released by comets, the roles of comets in planetary systems, clues to the importance of comets in producing dust in our zodiacal cloud as well as circumstellar dust around other stars, and the links between collected meteoritic samples with a known cometary body. Samples are collected in newly invented continuous gradient density silica aerogel. Stardust is facilitated by a magnificent trajectory designed to accomplish a complex and ambitious flyby sample return mission within the Discovery program restrictions. The remaining science payload, which provides important context for the captured samples, includes a time-of-flight spectrometer measuring the chemical and isotopic composition of dust grains; a polyvinylidene fluoride dust flux monitor determining dust flux profiles; a CCD camera for imaging Wild 2 coma and its nucleus; a shared X band transponder providing two-way Doppler shifts to estimate limits to Wild 2 mass and integrated dust fluence; and tracking of the spacecraft's attitude sensing for the detection of large particle impacts. The graphite composite spacecraft brings the collected sample back to Earth by a direct reentry in a capsule.
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was introduced into cosmochemistry about a decade ago. Major advantages of TOF-SIMS compared to other ion microprobe techniques are (a) parallel detection of all secondary ions with one polarity in a single measurement both polarities in subsequent analyses, (b) high lateral resolution, (c) sufficient mass resolution for separation of major mass interferences, and (d) little sample destruction. This combination makes TOF-SIMS highly suitable for the analysis especially of small samples, like interplanetary and presolar dust grains, as well as tiny inclusions within meteorites. Limitations of this technique are mainly referring to isotopic measurements and quantification. The possibility to measure molecular and atomic ion species simultaneously extends the applications of TOF-SIMS to the investigation of indigenous hydrocarbons in extraterrestrial material, which might have been essential for the formation of life. The present work gives an overview of TOF-SIMS in cosmochemistry, technical aspects as well as applications, principles of data evaluation and various results.
Stardust, the 4th Discovery mission launched in February 1999, will
collect coma samples from the recently deflected comet 81P/Wild 2 on 2
January 2004 and return them to Earth on 15 January 2006 for detailed
laboratory analyses. Stardust will be the first mission to bring samples
back to Earth from a known comet and also the first to bring back
contemporary interstellar particles recently discovered. These samples
should provide important insights into the nature and amount of dust
released by comets, the roles of comets in planetary systems, clues to
the importance of comets in producing dust in our zodiacal cloud as well
as circumstellar dust around other stars, and the links between
collected meteoritic samples with a known cometary body. Samples are
collected in newly invented continuous gradient density silica aerogel.
Stardust is facilitated by a magnificent trajectory designed to
accomplish a complex and ambitious flyby sample return mission within
the Discovery program restrictions. The remaining science payload, which
provides important context for the captured samples, includes a
time-of-flight spectrometer measuring the chemical and isotopic
composition of dust grains; a polyvinylidene fluoride dust flux monitor
determining dust flux profiles; a CCD camera for imaging Wild 2 coma and
its nucleus; a shared X band transponder providing two-way Doppler
shifts to estimate limits to Wild 2 mass and integrated dust fluence;
and tracking of the spacecraft's attitude sensing for the detection of
large particle impacts. The graphite composite spacecraft brings the
collected sample back to Earth by a direct reentry in a capsule.
Results are presented on an element-composition study conducted on 200 interplanetary dust particles (IDPs) collected with NASA's U2 and RB 47 aircraft at altitudes near 20 km. These IDPs could be classified into two major morphological types, i.e., the 'porous' and the 'smooth' particle types, which showed significant compositional differences. Namely, elemental abundances found in porous particles are closely matching those of the CI chondrites, while the smooth particle group displayed systematic Ca and Mg depletions and contained stoichiometric 'excess' oxygen, consistent with the presence of hydrous phases. This fact, together with the occurrence of carbonates, magnetite framboids, and layer silicates, provides evidence that at least a significant number of the smooth-type IDPs were processed by aqueous activity. It is hypothesized that extensive aqueous activity only occurs in asteroids (as opposed to comets) and that the smooth class of IDPs is of an asteroidal origin.
In January 2006, the Stardust mission will return the first samples from a solid solar-system body since Apollo, and the first samples of contemporary interstellar dust ever collected. Although sophisticated laboratory instruments exist for the analysis of Stardust samples, techniques for the recovery of particles and particle residues from aerogel collectors remain primitive. Here we describe our recent progress in developing techniques for extracting small volumes of aerogel, which we have called ``keystones,'' which completely contain particle impacts but minimize the damage to the surrounding aerogel collector. These keystones can be fixed to custom-designed micromachined silicon fixtures (so-called ``microforklifts''). In this configuration the samples are self-supporting, which can be advantageous in situations in which interference from a supporting substrate is undesirable. The keystones may also be extracted and placed onto a substrate without a fixture. We have also demonstrated the capability of homologously crushing these unmounted keystones for analysis techniques which demand flat samples.
- L Lemelle
- L Le
- A Lanzirotti
- F Langenhorst
- A N Krot
- L P Keller
- A T Kearsley
- D Joswiak
- D Jacob
- H Ishii
- R Harvey
- K Hagiya
- L Grossman
- J N Grossman
- G A Graham
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- Gillet Ph
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- A L Butterworth
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- J C Bridges
- S Brennan
- A Brearley
Lemelle L., Le L., Lanzirotti A., Langenhorst F., Krot A. N.,
Keller L. P., Kearsley A. T., Joswiak D., Jacob D., Ishii H.,
Harvey R., Hagiya K., Grossman L., Grossman J. N., Graham
G. A., Gounelle M., Gillet Ph., Genge M. J., Flynn G., Ferroir T.,
Fallon S., Ebel D. S., Dai Z. R., Cordier P., Clark B., Chi M.,
Butterworth A. L., Brownlee D. E., Bridges J. C., Brennan S.,
Brearley A., Bradley J. P., Bleuet P., Bland P. A., and Bastien R.
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Sandford S. A., Aléon J., Alexander C. M. O'D., Araki T., Bajt S.,
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J. R., Burchell M. J., Busemann H., Butterworth A., Clemett
S. J., Cody G., Colangeli L., Cooper G., d'Hendecourt L.,
Djouadi Z., Dworkin J. P., Ferrini G., Fleckenstein H., Flynn
G. J., Franchi I. A., Fries M., Gilles M. K., Glavin D. P.,
Gounelle M., Grossemy F., Jacobsen C., Keller L. P., Kilcoyne
A. L. D., Leitner J., Matrajt G., Meibom A., Mennella V.,
Mostefaoui S., Nittler L. R., Palumbo M. E., Papanastassiou
D. A., Robert F., Rotundi A., Snead C. J., Spencer M. K.,
Stadermann F. J., Steele A., Stephan T., Tsou P., Tyliszczak T.,
Westphal A. J., Wirick S., Wopenka B., Yabuta H., Zare R. N.,
and Zolensky M. E. 2006. Organics captured from comet 81P/
Wild 2 by the Stardust spacecraft. Science 314:1720-1724.
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- G Nakamura
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- T Newville
- M Papanastassiou
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- D Schwandt
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- T H Sheffield-Parker
- J Simionovici
- A Sitnitsky
- I Snead
- C J Stadermann
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- T Stroud
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- Y Sutton
- S R Taylor
- S Teslich
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- D Tsou
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- A Uesugi
T., Khodja H., Lanzirotti A., Leitner J., Lemelle L., Leroux H.,
Luening K., MacPherson G. J., Marhas K. K., Marcus M. A.,
Matrajt G., Nakamura T., Nakamura-Messenger K., Nakano T.,
Newville M., Papanastassiou D. A., Pianetta P., Rao W.,
Riekel C., Rietmeijer F. J. M., Rost D., Schwandt C. S., See T.
H., Sheffield-Parker J., Simionovici A., Sitnitsky I., Snead C. J.,
Stadermann F. J., Stephan T., Stroud R. M., Susini J., Suzuki Y.,
Sutton S. R., Taylor S., Teslich N., Troadec D., Tsou P.,
Tsuchiyama A., Uesugi K., Vekemans B., Vicenzi E. P.,
Vincze L., Westphal A. J., Wozniakiewicz P., Zinner E., and
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- J Gilmour
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- S Jones
- D Joswiak
- A Jurewicz
- A T Kearsley
- L P Keller
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- M.-C Liu
- K Luening
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- G Macpherson
- M A Marcus
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- G Matrajt
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- A Meibom
- V Mennella
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- S Mostefaoui
- T Nakamura
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- S A Sandford
- C S Schwandt
- T H See
- D Schlutter
- J Sheffield-Parker
- A Simionovici
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- I Sitnitsky
- C J Snead
- M K Spencer
- F J Stadermann
- A Steele
- T Stephan
- R Stroud
- J Susini
- S R Sutton
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- S Taylor
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Flynn G., Franchi I. A., Fries M., Gainsforth Z., Gallien J.-P.,
Genge M., Gilles M. K., Gillet Ph., Gilmour J., Glavin D. P.,
Gounelle M., Grady M. M., Graham G. A., Grant P. G., Green
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