An ocean is a large planetary body of liquid,a home to all sea creatures and plants.
Oceans exist above the mantle of some differentiated astronomical objects such as planet's surface, dwarf planets and natural satellites.The terms marine and oceanic apply to things relating to oceans.
Earth's global ocean is the largest known surface ocean.Approximately 71% of the planet's surface is covered by saline water that is customarily divided into several principal oceans and smaller seas.
It is the principal component of Earth's hydrosphere which is integral to all known life,forms part of the carbon cycle and influences climate and weather patterns. The total volume is approximately 1.3 billion cubic kilometers with an average depth of 3,790 meters(12,430 ft).
it is habitat of 230,00 species known to science, however much of the ocean's depths remain unexplored and it is estimated that over 2 million marine species may exist. The origin of Earth's oceans is still unknown.
Extraterrestrial oceans may be composed of a wide range of elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the Lakes of Titans though there is evidence for the existence of oceans elsewhere in the Solar system. Early in their geologic histories, Mars and Venus are theorised to like Earth have large water oceans, the Mars Ocean Hypothesis suggests that nearly a third of the surface of Mars was covered by water though Water on Mars is no longer oceanic while a Runaway greenhouse effect may have boiled away the global ocean of Venus.
