Geometric albedo For Earth-bound observers this occurs when the body in question is at opposition and on the ecliptic. The visual geometric albedo refers to the geometric albedo quantity when accounting for only electromagnetic radiation in the visible spectrum. The surface materials (regoliths) of airless bodies (in fact, the majority of bodies in the Solar System) are strongly non-Lambertian and exhibit the opposition effect, which is a strong tendency to reflect light straight back to its source, rather than scattering light diffusely. The geometric albedo of these bodies can be difficult to determine because of this, as their reflectance is strongly peaked
Classical albedo features on Mars used to describe geographical features on the planet. Early telescopic astronomers, observing Mars from a great distance through primitive instruments (though they were advanced for their day), were limited to studying albedo contrasts on the surface of the planet. These lighter and darker patches rarely correspond to topographic features and in many cases obscure them. The origins of the albedo contrasts were a mystery. The lighter patches at the poles were correctly believed to be a frozen substance, either water or carbon dioxide, but the nature of the dark patches seen against the general reddish tint of Mars was uncertain