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Filamentary enstatite crystals are found in interplanetary dust particles of likely cometary origin but are very rare or absent in meteorites. Crystallographic characteristics of filamentary enstatites indicate that they condensed directly from vapor. We measured the O isotopic composition of an enstatite ribbon from a giant cluster interplanetary dust particle to be $\delta^{18}\rm{O}{=25{\pm}55}$, $\delta^{17}\rm{O}{=-19{\pm}129}$, $\Delta^{17}\rm{O}{=-32{\pm}134}$ (2$\sigma$ errors), which is inconsistent at the 2$\sigma$ level with the composition of the Sun inferred from the Genesis solar wind measurements. The particle's O isotopic composition, consistent with the terrestrial composition, implies that it condensed from a gas of non-solar O isotopic composition, possibly as a result of vaporization of disk region enriched in $^{16}$O-depleted solids. The relative scarcity of filamentary enstatite in asteroids compared to comets implies either that this crystal condensed from dust vaporized \textit{in-situ} in the outer Solar System where comets formed, or it condensed in the inner Solar System and was subsequently transported outward to the comet-forming region.

In a consortium analysis of a large particle captured from the coma of comet 81P/Wild 2 by the Stardust spacecraft, we report the discovery of a field of fine-grained material (FGM) in contact with a large sulfide particle. The FGM was partially located in an embayment in the sulfide, so appears to have been largely protected from damage during hypervelocity capture in aerogel. Some of the FGM particles are indistinguishable in their characteristics from common components of chondritic-porous interplanetary dust particles (CP-IDPs), including glass with embedded metals and sulfides (GEMS) and equilibrated aggregates (EAs). The sulfide exhibits surprising Ni-rich lamellae, which may indicate that this particle experienced a long-duration heating event after its formation but before incorporation into Wild 2. We discuss the relationship of the FGM to the sulfide, to other Wild 2 particles and to the history of the Solar nebula.

We analyzed 2 ultra-carbonaceous interplanetary dust particles and 2 cometary Wild 2 particles with infrared spectroscopy. We characterized the carrier of the 3.4 micron band in these samples and compared its profile and the CH2/CH3 ratios to the 3.4 micron band in the diffuse interstellar medium (DISM), in the insoluble organic matter (IOM) from 3 primitive meteorites, in asteroid 24 Themis and in the coma of comet 103P/Hartley 2. We found that the 3.4 micron band in both Wild 2 and IDPs is similar, but different from all the other astrophysical environments that we compared to. The 3.4 micron band in IDPs and Wild 2 particles is dominated by CH2 groups, the peaks are narrower and stronger than in the meteorites, asteroid Themis, and the DISM. Also, the presence of the carbonyl group C=O at 1700 cm-1 (5.8 micron) in most of the spectra of our samples, indicates that these aliphatic chains have O bonded to them, which is quite different from astronomical spectra of the DISM. Based on all these observations we conclude that the origin of the carrier of the 3.4 micron band in IDPs and Wild 2 samples is not interstellar, instead, we suggest that the origin lies in the outermost parts of the solar nebula., Comment: 50 pages, 20 figures, 3 tables