The Gamma Ray Spectrometer (GRS) is a significant component of NASA's Mars Surveyor Program. This is an ongoing initiative to explore Mars through scientific instruments aboard orbiters, landers, and rovers. GRS is really a suite of three instruments designed to analyze the chemical composition of the Martian surface. GRS also has the capability of detecting water in shallow subsurface depths. The data provided by GRS will be used to determine the elemental abundances of the major geological regions of Mars. This will include a global map of water deposits, their variation with depth near the surface, and the seasonal changes of the polar ice caps. In addition, GRS will participate in the study of cosmic gamma ray bursts.