Ray system they have been identified on Mars in infrared images taken from orbit by "2001 Mars Odyssey"s thermal imager. Rays appear at visible, and in some cases infrared wavelengths, when ejecta are made of material with different reflectivity (i.e., albedo) or thermal properties from the surface on which they are deposited. Typically, visible rays have a higher albedo than the surrounding surface. More rarely an impact will excavate low albedo material, for example basaltic-lava deposits on the lunar maria. Thermal rays, as seen on Mars, are especially apparent at night when slopes and shadows do not influence the infrared energy emitted
Classical albedo features on Mars topographic features on Mars are still based on the classical nomenclature for the feature's location; for instance, the albedo feature 'Ascraeus Lacus' provides the basis of the name of the volcano "Ascraeus Mons" in roughly the same position. In addition, since most Earth-based amateur telescopes are not powerful enough to resolve the topographic surface features of Mars, amateur astronomers still use many of the old feature-names to orient themselves and record their observations. Several Latin words involved here are common nouns. These are generally, but not always, second in the name, but are usually ignored in alphabetizing below: Not listed