Ocean Ocean An ocean () is a body of saline water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word "ocean" is often used interchangeably with "sea" in American English. Strictly speaking, a "sea" is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land, though "the sea" refers also to the oceans. Saline water covers approximately and is customarily divided into
NASA Earth Science chemistry, ocean and land ecosystems. It was a NASA scientist, Dr. James Hansen, who first alerted the world to the dangers of global warming due to greenhouse gases emitted by human burning of fossil fuels. Earth Science research also provides the foundations of understanding for the search for extraterrestrial life through the NASA Astrobiology Institute (NAI), in which the focus is often on the extreme conditions for life to survive. NASA Earth Science NASA Earth Science, formerly called the NASA Earth Science Enterprise (ESE), formerly called Mission To Planet Earth (MTPE), is a NASA research program "to develop a scientific