A spectrometer is a device used to measure the intensity of light at various wavelengths. It is used in a wide variety of scientific fields, including astronomy, chemistry, geology, and medicine. In the context of planetary science, spectrometers are used to collect information about the composition of celestial objects by analyzing the light they emit or reflect. By measuring the intensity of light at different wavelengths, scientists can identify the presence of specific elements and molecules in the atmosphere or surface of a planet or moon. This information can provide valuable insights into the geological and chemical processes that have shaped these extraterrestrial bodies.