White Mountain Region, Moscow, Russia

Exogeology deals with planetary mountains, which in that branch of science are usually called montes (singular—mons). The highest mountain on earth is the Mount Everest 8,848 m (29,029 ft). The highest known mountain in the Solar System is Olympus Mons on the planet Mars at 21,171 m (69,459 ft).
Definition
There is no universally accepted definition of a mountain. Elevation, volume, relief, steepness, spacing and continuity has been used as criteria for defining a mountain. In the Oxford English Dictionary a mountain is defined as "a natural elevation of the earth surface rising more or less abruptly from the surrounding level and attaining an altitude which, relatively to the adjacent elevation, is impressive or notable."