Albedo planet would drop to about 0 °C. In contrast, if the entire Earth was covered by water — a so-called aquaplanet — the average temperature on the planet would rise to almost 27 °C. For land surfaces, it has been shown that the albedo at a particular solar zenith angle "θ" can be approximated by the proportionate sum of two terms: the directional-hemispherical reflectance at that solar zenith angle, formula_1, and the bi-hemispherical reflectance, formula_2, with formula_3 being the proportion of direct radiation from a given solar angle, and formula_4 being the proportion of diffuse illumination. Hence, the actual albedo
Martian surface Rocky materials do not vary much in density and specific heat, so variations in thermal inertia are mainly due to variations in thermal conductivity. Solid rock surfaces, such as outcroppings, have high thermal conductivities and inertias. Dust and small granular material in the regolith have low thermal inertias because the void spaces between grains restrict thermal conductivity to the contact point between grains. Thermal inertia values for most of the Martian surface are inversely related to albedo. Thus, high albedo areas have low thermal inertias indicating surfaces that are covered with dust and other fine granular material. The dark gray,