Editing Polar ice cap (section)

{{short description|High-latitude region of an astronomical body with major parts covered in ice}}
{{about|polar ice caps in general|Earth's ice cap|Arctic ice pack}}
{{redirect|Polar ice|the vodka|Polar Ice (vodka)}}
{{Use dmy dates|date=December 2018}}
[[File:Mars, as seen by the Hubble  Telescope.jpg|thumb|The [[Martian polar ice caps|polar ice caps]] on [[Mars]], with the entire north one visible, as imaged through the [[Hubble Space Telescope]]]]

A '''polar ice cap''' or '''polar cap''' is a high-[[latitude]] region of a [[planet]], [[dwarf planet]], or [[natural satellite]] that is covered in [[ice]].<ref>[http://nsidc.org/cgi-bin/words/letter.pl?P The National Snow and Ice Data Center Glossary] {{webarchive|url=http://arquivo.pt/wayback/20090710225721/http://nsidc.org/cgi-bin/words/letter.pl?P |date=10 July 2009 }}</ref>

There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land, but only that it must be a body of solid phase matter in the [[polar region]]. This causes the term "polar ice cap" to be something of a misnomer, as the term [[ice cap]] itself is applied more narrowly to bodies that are over land, and cover less than 50,000&nbsp;km<sup>2</sup>: larger bodies are referred to as [[ice sheets]].

The composition of the ice will vary. For example, Earth's polar caps are mainly water ice, whereas [[Mars]]'s polar ice caps are a mixture of [[Dry ice|solid carbon dioxide]] and water ice.

Polar ice caps form because high-latitude regions receive less energy in the form of [[solar radiation]] from the Sun than [[equator]]ial regions, resulting in lower surface temperatures.

Earth's polar caps have changed dramatically over the last 12,000 years. [[Season]]al variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the Sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to [[climate]] change.