Joint analysis of visible and infrared images

Analysis of data combining daytime visible reflected, daytime IR emitted, and nighttime IR emitted images allows us to isolate the physical effects of topography, albedo, and thermal inertia. To a good approximation, these physical influences interact linearly so that maps showing topographic shading, albedo, and relative thermal inertia can be produced by simple algebraic manipulation of the co-registered images. The shading map resembles an airbrush, shaded relief portrayal of the surface, and can be used as the input for quantitative reconstruction of topography by photoclinometry (shape-fromshading). We demonstrate the method with imagery from the NASA 2001 Mars Odyssey Thermal Emission Imaging System (THEMIS), a dataset that could support mapping most of Mars in this way at 100 m resolution.