Albedo reflectance and bi-hemispherical reflectance (e.g.,). These calculations are based on the bidirectional reflectance distribution function (BRDF), which describes how the reflectance of a given surface depends on the view angle of the observer and the solar angle. BDRF can facilitate translations of observations of reflectance into albedo. Earth's average surface temperature due to its albedo and the greenhouse effect is currently about 15 °C. If Earth were frozen entirely (and hence be more reflective), the average temperature of the planet would drop below −40 °C. If only the continental land masses became covered by glaciers, the mean temperature of the
Albedo feature has fallen somewhat into disuse. It is however still used for Earth-based observing of Mars by amateur astronomers. However, for some Solar System bodies (such as Pluto prior to the New Horizons mission), the best available images show only albedo features. These images were usually taken by the Hubble Space Telescope or by ground-based telescopes using adaptive optics. Cydonia Mensae on Mars is an example of an albedo feature. Albedo feature An albedo feature is a large area on the surface of a planet (or other solar system body) which shows a contrast in brightness or darkness (albedo) with adjacent