Polar ice caps are referred to a high-latitude expanse of a planet or moon that has been sheeted in ice. To be defined as polar ice caps there are no set prerequisites as per the size or composition for a body of ice, even the geological pre-condition to be over the land surface does not exist. However, the only condition that requires to be fulfilled is that it should be body of solid phase matter located in the polar region. Ice cap itself is applicable judiciously as such bodies are ought to be placed over land, and have a surface area of lesser than 50,000 sq. km. the bodies larger would be considered as ice sheets.
It is to be noted that composition of the ice is subject to variation. For instance, the polar caps on Earth are composed of water ice whereas on Mars polar ice caps are a mixture of water ice as well as solid phase carbon dioxide.
The formation of polar ice caps is primarily owing to the fact that the high-latitude areas get less force of solar radiation from the sun as compared to the equatorial regions. Seasonal differences of the ice caps would occur in compliance with the varied absorption of solar energy while the planet or moon revolves around the sun. In addition to this, as per the geologic time scale, the rise or reduction in the size of ice caps may take place owing to the climatic disparity.