This page is about the bodies of water designated as oceans. For other uses of the word, see Ocean (disambiguation).
Almost three quarters (71%) of the surface of the Earth is covered by ocean. This global, interconnected body of salt water
is divided by the continents and larger archipelagos into five oceans as follows:
Southern Ocean — by some reckonings the Southern Ocean is not an ocean in its own right, and is divided among the Atlantic, Indian and Pacific oceans.
The boundaries between the oceans are set by the International Hydrographic Organization; e.g., the Southern Ocean extends from the coast of Antarctica to 60 degrees south latitude. Smaller regions of the oceans are known as seas, gulfs, straits, etc.
See sea water for a detailed discussion of ocean water composition, most notably its salinity.
Study of Earth's oceans is called oceanography. Travel on the surface of the ocean through the use of boats dates back to prehistoric times, but only in modern times has extensive underwater travel become possible.
The deepest point in the ocean is the Mariana Trench located in the Pacific Ocean near the Northern Mariana Islands. It has a maximum depth of 10,924 m (35,838 ft). It was fully surveyed in 1951 by the British navy vessel, "Challenger II" which gave its name to the deepest part of the trench, the "Challenger Deep".
There is currently much debate over whether Mars once had an ocean of water, and over what happened to it if it did; recent findings by the Mars Exploration Rover mission indicate that it had some long-term standing water in at least one location, but its extent is not known.
Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than an "ocean". The distribution of these liquid regions will hopefully be better known after the arrival of the Cassini-Huygens Mission, which will drop its Huygens probe onto Titan in January 2005.
