This map of Mars indicates locations of new craters that have excavated ice (blue) and those that have not (red). The underlying map is based on the brightness, or albedo, of the Martian surface. Most fresh craters are discovered in the brighter, dusty regions of Mars where dark blast patterns from the impacts can be seen.
The albedo information comes from the Thermal Emission Spectrometer on NASA's Mars Odyssey orbiter. Surface topographical information for the map comes from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor orbiter.