His research specialties are spectroscopy and radiometry of planets and small bodies in the Solar System. These small bodies include comets, asteroids, planetary satellites, dwarf planets (e.g., Pluto), and objects in the region beyond Neptune (Kuiper Belt objects and trans-Neptunian bodies). He uses spectroscopic observations made with ground-based and space-based telescopes, as well as interplanetary spacecraft, to identify and study the ices, minerals, and organic materials that compose the surfaces of planets and small bodies. Together with several colleagues, Cruikshank has found many kinds of ice on several small planetary bodies. These include frozen CH4, N2, CO, CO2, and H2O on Neptune’s satellite Triton, CH4, N3, and CO on Pluto, H2O on Pluto’s satellite Charon, H20 ice on many of the moons of Saturn and Uranus, H2O and CH3OH on the Centaur object 5145 Pholus. In studies with the Cassini spacecraft, he and his colleagues have found hydrocarbons on several of Saturn’s satellites.