albedo

Albedo is a measure of reflectance of a body, i.e., the fraction of incoming light, or any other electromagnetic radiation (EMR), that is reflected. The Earth's albedo varies over the planet and conditions: water versus land, snow cover, cloud cover, city versus country, forest versus desert. The general albedo of a planet or moon can be inferred from calculated incoming versus observed outgoing EMR, and provides clues regarding its material and atmosphere.

Albedo features are regions on a planet or moon with a noticeably higher or lower albedo than their surroundings. Mars and Mercury show such features (as do the Earth and the Moon).

A body's geometric albedo compares the light specifically reflected back toward the source against the amount of light that a disk of the same diameter would reflect back toward the source if it was scattering its reflected light with no preferred direction. Some planet and moon surfaces don't diffuse the light in such a random manner, reflecting a larger portion straight back toward the source, effectively acting as a retroreflector such as those used on bicycles and highway signs. Bodies with this property have a geometric albedo greater than 1.

A body's Bond albedo is essentially the mean albedo over the surface of a body.