Impact crater. Scanning Electron Micrograph (SEM) of a tiny crater in the surface of a window of Space Shuttle Challenger, following mission STS-7 of 18-24 June 1983. The crater is about 640 microns in diameter and 630 microns in depth, surrounded by a spall zone of 2.4 millimetres diameter. The spall zone is an area of microscopic craters made by debris from the initial impact event. The pit contains some titanium oxide, which possibly originated from a flake of paint. Mission STS-7 carried the first US woman into space, Sally Ride, launched two satellites and performed one satellite retrieval. Magnification: x360 at 8x10 inch size; x100 at 5x7cm size.