Classification of the Johnson Space Center stratospheric dust collection

The NASA Johnson Space Center stratospheric dust collection program has made available to the scientific community a rare set of materials for studies of (1) extraterrestrial materials germane to the early history of the solar system and (2) natural and man-made terrestrial materials in the stratosphere. A review of the first 291 cataloged particles provides a basis for a reliable taxonomy of all stratospheric particles. Data used in this review include particle shape, size, bulk chemistry, and texture. Extraterrestrial materials occur in all three defined categories: spheres, aggregates, and fragments. Approximately 76% of aggregates are of probable extraterrestrial origin. Spheres contain the least amount of extraterrestrial material (∼43%). A number of new groups of stratospheric particles have been identified. These include aluminum and silicate aggregates, aluminum fragments, and aluminum prime spheres and fragments. Limitations to the use of this classification scheme are based primarily upon the lack of additional data to unambiguously define particle origin.