A Spherule from the Earth's Moon

Explanation: How did this spherule come to be on the Moon? When a meteorite strikes the Moon , the energy of the impact melts some of the splattering rock , a fraction of which might cool into tiny glass beads . Many of these glass beads were present in lunar soil samples returned to Earth by the Apollo missions . Pictured above is one such glass spherule that measures only a quarter of a millimeter across. This spherule is particularly interesting because it has been victim to an even smaller impact. A miniature crater is visible on the upper left, surrounded by a fragmented area caused by the shockwaves of the small impact. By dating many of these impacts , astronomers can estimate the history of cratering on our Moon.