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Friday, 23 September 2016
Water is the famous name in the world.do you know about the water in the space.? Just read the passage. Extraterrestrial liquid water (from theLatin words: extra ["outside of, beyond"] and terrestris ["of or belonging to Earth"]) is water in its liquid state that is found beyond Earth. It is a subject of wide interest because it is commonly thought to be one of the key prerequisites forextraterrestrial life.
With oceanic water covering 71% of its surface, Earth is the only planet known to have stable bodies of liquid water on its surface,and liquid water is essential to all known life forms on Earth. The presence of water on the surface of Earth is a product of its atmospheric pressure and a stable orbit in the Sun's circumstellar habitable zone, though the origin of Earth's waterremains unknown.
The main methods currently used for confirmation are absorption spectroscopy and geochemistry. These techniques have proven effective for atmospheric water vapour and ice. However, using current methods ofastronomical spectroscopy it is substantially more difficult to detect liquid water on terrestrial planets, especially in the case of subsurface water. Due to this, astronomers, astrobiologists and planetary scientists use habitable zone, gravitational andtidal theory, models of planetary differentiation and radiometry to determine potential for liquid water. Water observed in volcanic activity can provide more compelling indirect evidence, as can fluvial features and the presence of antifreeze agents, such as salts or ammonia.
Using such methods, many scientists infer that liquid water once covered large areas of Mars and Venus.Water is thought to exist as liquid beneath the surface of some planetary bodies, similar to groundwater on Earth. Water vapour is sometimes considered conclusive evidence for the presence of liquid water, although atmospheric water vapour may be found to exist in many places where liquid water does not. Similar indirect evidence, however, supports the existence of liquids below the surface of several moons and dwarf planets elsewhere in the Solar System.Some are speculated to be largeextraterrestrial "oceans".Liquid water is thought to be common in otherplanetary systems, despite the lack of conclusive evidence, and there is a growing list of extrasolar candidates for liquid water.
Liquid water in the Solar System
As of December 2015, the confirmed liquid water in the Solar System outside Earth is 25-50 times the volume of Earth's water (1.3 billion cubic kilometers).
Water on Mars exists today almost exclusively as ice, with a small amount present in the atmosphere as vapour. Some liquid water may occur transiently on the Martian surface today but only under certain conditions. No large standing bodies of liquid water exist because the atmospheric pressure at the surface averages just 600 pascals(0.087 psi)—about 0.6% of Earth's mean sea level pressure—and because the global average temperature is far too low (210 K (−63 °C)), leading to either rapid evaporation or freezing. On 28 September 2015, NASA announced that they found evidence that the recurring slope lineae are caused by flows ofbrine — hydrated salts.
Scientists' consensus is that a layer of liquid water exists beneath Europa's (moon of Jupiter) surface, and that heat from tidal flexing allows the subsurface ocean to remain liquid. It is estimated that the outer crust of solid ice is approximately 10–30 km (6–19 mi) thick, including a ductile "warm ice" layer, which could mean that the liquid ocean underneath may be about 100 km (60 mi) deep.This leads to a volume of Europa's oceans of 3 × 1018 m3, slightly more than two times the volume of Earth's oceans.
Enceladus, a moon of Saturn, has shown geysers of water, confirmed by the Cassini spacecraft in 2005 and analyzed more deeply in 2008. Gravimetric data in 2010-2011 confirmed a subsurface ocean. While previously believed to be localized, most likely in a portion of the southern hemisphere, evidence revealed in 2015 now suggests the subsurface ocean is global in nature.
In addition to water, these geysers from vents near the south pole contained small amounts of salt, nitrogen, carbon dioxide, and volatile hydrocarbons. The melting of the ocean water and the geysers appear to be driven by tidal fluxfrom Saturn.
A subsurface saline ocean is theorized to exist on Ganymede, a moon ofJupiter, following observation by theHubble Space Telescope in 2015. Patterns in auroral belts and rocking of the magnetic field suggest the presence of an ocean. It is estimated to be 100 km deep with the surface lying below a crust of 150 km of ice.
Ceres appears to be differentiated into arocky core and icy mantle, and may have a remnant internal ocean of liquid water under the layer of ice.The surface is probably a mixture ofwater ice and various hydrated minerals such as carbonates and clay. In January 2014, emissions of water vapor were detected from several regions of Ceres. This was unexpected, because large bodies in the asteroid belt do not typically emit vapor, a hallmark of comets. Ceres also features a mountain called Ahuna Mons that is thought to be a cryovolcanic dome that facilitates the movement of high viscosity cryovolcanic magma consisting of water ice softened by its content of salts.