Textures and isotopic compositions of carbonaceous materials in A and B-type Stardust tracks: Track 130 (Bidi), track 141 (Coki) and track 80 (Tule)

We analyzed carbonaceous materials in the two main morphological types of Stardust tracks (A, and B). We analyzed 71 particles (∼1-10 μm in size) distributed along these tracks with transmission electron microscopy (TEM) and found carbon associated with 16 of them. The carbonaceous materials occur in five distinct morphologies: graphitic, smooth, dirty, spongy and globular, covering most of the range of morphologies observed in primitive meteorites and interplanetary dust particles. We measured N and C isotopic compositions on 5 of these particles and found that all but one have terrestrial isotopic compositions. The anomalous particle had a moderate 15N enrichment (δ15N = 150 ± 36‰, 2σ) and both globular and spongy morphologies. The carbonaceous materials are not preferentially associated with particles of a particular size but are randomly distributed in all three tracks.