Albedo their reflectivities. Fresh 'black' ice exhibits Fresnel reflection. Snow on top of this sea ice increases the albedo to 0.9. Cloud albedo has substantial influence over atmospheric temperatures. Different types of clouds exhibit different reflectivity, theoretically ranging in albedo from a minimum of near 0 to a maximum approaching 0.8. "On any given day, about half of Earth is covered by clouds, which reflect more sunlight than land and water. Clouds keep Earth cool by reflecting sunlight, but they can also serve as blankets to trap warmth." Albedo and climate in some areas are affected by artificial clouds, such as
Martian surface little light at the blue end of the spectrum but much at red and higher wavelengths. This is why Mars has the familiar reddish-orange color to the naked eye. But detailed observations reveal a subtle range of colors on Mars' surface. Color variations provide clues to the composition of surface materials. The bright areas are reddish-ochre in color, and the dark areas appear dark gray. A third type of area, intermediate in color and albedo, is also present and thought to represent regions containing a mixture of the material from the bright and dark areas. The dark gray areas can