Description: Illustration of a deep crater on the surface of the moon. Water from an encounter with an icy comet has collected in the perpetual shade of a deep crater on the surface of the moon, where the temperature is a constant - 380å¼ F. In 1998, the unmanned Lunar Prospector probe discovered evidence for water ice on the surface of the moon. Some scientists believe that as much as 10 to 300 million tons of ice may reside at the moon's North and South poles. The source of the ice is thought to be from one or more comets that struck the moon's surface four billion years ago. (It is thought that Earth's water may have come from comets as well.) Unfortunately, the moon's small size and lack of an atmosphere caused it to lose nearly all of its accumulated water to space. Any water that does remain on the moon would likely be on the poles, hidden in craters and depressions shaded from the Sun.
