Abstract
Introduction. Samples of rock, mineral, and glass fragments returned by Apollo 11 and 12 contain a variety of microcraters which were formed by the impacts of small projectiles. The craters are especially prominent in some of the small glass spherules and related forms.Crater types. It is possible to classify these microcraters on the basis of morphology as seen by the scanning electron microscope. Type I microcraters (Figure 1) show the following characteristics:A. A glassy central area is present which has been melted by the impact. This glass is primarily material from the target but may also contain melted projectile material. The central area is normally very smooth and may or may not have a smooth raised lip.
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