Albedo feature(glossary entry)
This is one of 18 different categories of lunar features recognized in the current system of IAU nomenclature. Albedo is a technical term related to non-topographic variations in surface properties which give rise to variations in the reflectance of planetary surfaces. The boundaries of features in this category are defined by changes in the darkness of the surface material as opposed to the variations in relief (surface height) that characterize all the other categories.
- Although there are many albedo features on the Moon, there is only one officially named feature in this category: Reiner Gamma.
- A preliminary draft of the IAU Planetary Gazetteer mentioned in its Introduction (page v) that "Most Lunar albedo features have been given formal names. The exception is Reiner Gamma, an enigmatic feature. The next version of the gazetteer will include all albedo names..." However, no additional lunar albedo feature names were listed in later versions.
- The maps of the System of Lunar Craters included a number of brightness "spots", most of which were given Roman letters (most often "Z"), indistinguishable from those used for craters. Most of these, indeed, prove to be bright-rayed craters too small to be resolved in the Earth-based photos on which the maps were based.
- The large mosaic of images obtained by the Clementine spacecraft is often referred to as an "albedo map" of the Moon because the images were obtained with the Sun near the longitude of the features being photographed; however it is an albedo map only near the Moon's equator and does not represent the albedo features seen from Earth as accurately as an Earth-based image of the Full Moon.