Morphology and internal structure of Antarctic cosmic dust spherules: Possible links to meteorite fusion crusts

Petrographic and SEM comparison of the outer morphology of different Antarctic spherules with their internal structure helped to distinguish those spherules that resulted from melting of micrometeorites from the ablation products of meteorites. A chain of possible transformations beginning with unmelted micrometeorites was recognized. Such structural transformations could begin from unmelted cosmic dust of olivine aggregates through granular spherules, to vitrophyric spherules with ghost-olivine glassy ovoidal objects, to vitrophyric, and to skeletal spherules. The fusion crusts of meteorites studied, showed that ablation can also produce a variety of spherules. Achondrites could produce glassy smooth, and internally compact holohyaline spherules, whereas chondrites could generate spherules of the rough glazed, dendrite decorated morphological types