Abstract: Reflectance spectroscopy is a powerful tool for remote sensing study of the terrestrial planets in solar system. From thermal infrared to far-ultraviolet, reflectance spectroscopy has been widely used to study the mineralogy of Mars and the Moon and thus to understand their surface processes and evolution histories. In this talk, two spectrometers for Mars, ESA's Mars Express OMEGA and NASA's MRO CRISM, used to identify ancient records of environmental change on Mars because of its sensitivity to minerals that represent water–rock interaction will be introduced. The methods on how to use DISORT radiative transfer model to do atmospheric corrections of the spectra from the two spectrometers and how to perform spectral unmixing analysis on atmospherically corrected reflectance spectra will be presented. Two areas on Mars were investigated using the methods we developed, and the inferred aqueous history on Mars will be discussed. Finally, a far-UV spectrograph named the Lyman Alpha Mapping Project (LAMP) onboard NASA's Lunar Reconnaissance Orbiter (LRO) will be introduced. The major scientific discoveries in the study of the Moon by the LAMP instrument will be briefly reviewed, and the initial results from photometrical modeling of the Moon in far-UV wavelengths will be also presented.