Geometric albedo node of their orbit, and hence lie on the ecliptic. In practice, measurements at small nonzero phase angles are used to derive the parameters which characterize the directional reflectance properties for the body (Hapke parameters). The reflectance function described by these can then be extrapolated to zero phase angle to obtain an estimate of the geometric albedo. For very bright, solid, airless objects such as Saturn's moons Enceladus and Tethys, whose total reflectance (Bond albedo) is close to one, a strong opposition effect combines with the high Bond albedo to give them a geometric albedo above unity (1.4 in the
Cerberus (Martian albedo feature) showing no large craters with diameters 500 m superimposed on Western Cerberus Plains lavas indicate the same surface is younger than 49 Ma. Cerberus (Martian albedo feature) Cerberus is a large "dark spot" (an albedo feature) located on Mars and named after the mythical dog Cerberus. The arcuate markings in the upper right are in the Amazonis plains and may be sand drifts. The Elysium volcano, a yellow area north of Cerberus, has several channels radiating from its flanks. The three bright spots, upper left, are volcanoes partially veiled by thin clouds. High resolution images show the bulk of the