Recent mineralogical and geochemical studies of interplanetary dust particles (IDPs) provide convincing evidence that they contain materials that formed in the early solar nebula. Some chondritic IDPs contain hydrated phases and may be related to CI and CM carbonaceous chondrites. However, detailed mineralogical data of the hydrated IDPs are extremely limited. We report here the results of transmission electron microscope (TEM) observations of a hydrated IDP containing Fe-, Mg-rich smectite or mica as a major phase. The sheet silicate appears to have formed by alteration of anhydrous silicates. Fassaite, a Ca, Al clinopyroxene, also occurs in this particle, and one of the crystals exhibits solar-flare tracks, clearly indicating that it is extraterrestrial. Fassaite is a major constituent of the Ca-, Al-rich refractory inclusions (CAIs) found in the carbonaceous chondrites. Its presence in this particle, therefore, suggests that there may be a link between hydrated IDPs and carbonaceous chondrites in the early history of the Solar System.
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