Ice planet

This article is about the type of planet smaller than giant planets. For the film, see Ice Planet (film). For the type of giant planet, see ice giant.

An ice planet is a type of hypothetical exoplanet with an icy surface of volatiles such as water, ammonia, and methane. Ice planets consist of a global cryosphere. They are bigger versions of the minor planets of the Solar System, which includes the icy moons Europa, Enceladus, and Triton, the dwarf planets Pluto and Eris, and many other icy small Solar System bodies such as comets.

Characteristics and habitability

Ice planets usually appear nearly white with geometric albedos of more than 0.9. An ice planet's surface can be composed of water, methane, ammonia, carbon dioxide (known as "dry ice"), carbon monoxide, and other volatiles, depending on its surface temperature. Ice planets would have surface temperatures below 260 K if composed primarily of water, below 180 K if primarily composed of CO2 and ammonia, and below 80 K if composed primarily of methane.

On the surface, ice planets are hostile to life forms like those living on Earth because they are very cold. Many ice worlds likely have subsurface oceans, warmed by internal heat or tidal forces from another nearby body. Liquid subsurface water would provide habitable conditions for life, including fish, plankton, and microorganisms. Subsurface plants cannot exist because there is no light for photosynthesis. Microorganisms can produce nutrients using specific chemicals (chemosynthesis). Some planets, if conditions are right, may have significant atmospheres and surface liquids like Saturn's moon Titan, which could be habitable for exotic forms of life.

Pluto and candidates

OGLE-2005-BLG-390Lb is likely an ice planet

Although there are many icy objects in the Solar System, there are no known ice planets (though Pluto was considered an ice planet until its reclassification in 2006).[1] There are several extrasolar ice planet candidates, including OGLE-2005-BLG-390Lb, OGLE-2013-BLG-0341L b and MOA-2007-BLG-192Lb.

See also

References

  1. ↑ Stern, Alan; Mitton, Jacqueline (2005). "Pluto and Charon : ice worlds on the ragged edge of the solar system". Weinheim: Wiley-VCH. Retrieved July 13, 2013.
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