page_title: Ocean
section_title: Extrasolar
hierarchical_section_title: Ocean / Extraterrestrial oceans / Extrasolar
caption_attribution_description: English: Extrasolar planet Upsilon Andromedae d lies in the habitable zone and if it has moons large enough, they may be able to support liquid water, as the image shows. On the horizon of this hypothetical earth-like moon can be seen Upsilon Andromedae d, possibly a class II planet (Sudarsky classification): since it is too warm to form ammonia clouds, the visible top ones are mostly made up of water vapor, white in colour instead of the characteristic yellow-reddish clouds of Jupiter and Saturn, and with some bluish hue due to the rayleigh scatterig.
context_page_description: An ocean is a body of 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, and Arctic Oceans. The phrases "the ocean" or "the sea" used without specification refer to the interconnected body of salt water covering the majority of the Earth's surface. As a general term, "the ocean" is mostly interchangeable with "the sea" in American English, but not in British English. Strictly speaking, a sea is a body of water partly or fully enclosed by land.
  Saline seawater covers approximately 361,000,000 km² and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of Earth's surface and 90% of the Earth's biosphere. The ocean contains 97% of Earth's water, and oceanographers have stated that less than 20% of the World Ocean has been mapped. The total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters.
context_section_description: Some planets and natural satellites outside the Solar System are likely to have oceans, including possible water ocean planets similar to Earth in the habitable zone or "liquid-water belt". The detection of oceans, even through the spectroscopy method, however is likely extremely difficult and inconclusive.
  Theoretical models have been used to predict with high probability that GJ 1214 b, detected by transit, is composed of exotic form of ice VII, making up 75% of its mass,
  making it an ocean planet.
  Other possible candidates are merely speculated based on their mass and position in the habitable zone include planet though little is actually known of their composition. Some scientists speculate Kepler-22b may be an "ocean-like" planet. Models have been proposed for Gliese 581 d that could include surface oceans. Gliese 436 b is speculated to have an ocean of "hot ice". Exomoons orbiting planets, particularly gas giants within their parent star's habitable zone may theoretically have surface oceans.
  Terrestrial planets will acquire water during their accretion, some of which will be buried in the magma ocean but most of it will go into a steam atmosphere, and when the atmosphere cools it will collapse on to the surface forming an ocean. There will also be outgassing of water from the mantle as the magma solidifies—this will happen even for planets with a low percentage of their mass composed of water, so "super-Earth exoplanets may be expected to commonly produce water oceans within tens to hundreds of millions of years of their last major accretionary impact."
caption: Rendering of a hypothetical large extrasolar moon with surface liquid-water oceans
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "96", "Image YResolution": "96", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS3 Windows", "Image DateTime": "2011:02:12 19:25:00", "Image ExifOffset": "164", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "302", "Thumbnail JPEGInterchangeFormatLength": "5778", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "735", "EXIF ExifImageLength": "474"}