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Most water in Earth's atmosphere and crust comes from saline seawater, while fresh water accounts for nearly 1% of the total. The vast bulk of the water on Earth is saline or salt water, with an average salinity of 35‰ (or 3.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land.
[9] Fresh water resources are unevenly distributed in terms of space and time and can go from floods to water shortages within months in the same area. In 1998, 76% of the total population had a specific water availability of less than 5.0 thousand m 3 per year per capita.
Groundwater is fresh water located in the subsurface pore space of soil and rocks.It is also water that is flowing within aquifers below the water table.Sometimes it is useful to make a distinction between groundwater that is closely associated with surface water, and deep groundwater in an aquifer (called "fossil water" if it infiltrated into the ground millennia ago [8]).
NASA says its scientists found that water on Jupiter-family Comet 67P/Churyumov–Gerasimenko, the first comet to be orbited and landed upon by robotic spacecraft from Earth, had a similar ...
Fresh water is the water resource that is of the most and immediate use to humans. Fresh water is not always potable water, that is, water safe to drink by humans. Much of the earth's fresh water (on the surface and groundwater) is to a substantial degree unsuitable for human consumption without treatment.
Astronomers used the Hubble Space Telescope to make a landmark discovery of water vapor in the atmosphere of a planet just twice Earth’s diameter in size.
In 2007, such a disk was found in the habitable zone of MWC 480. [79] In 2008, such a disk was found around the star AA Tauri. [80] In 2009, a similar disk was discovered around the young star HD 142527. [81] In 2013, a water-rich debris disk around GD 61 accompanied by a confirmed rocky object consisting of magnesium, silicon, iron, and oxygen.
Two 4.5 billion-year-old meteorites found on Earth that contained liquid water alongside a wide diversity of deuterium-poor organic compounds further support this. [44] Earth's current deuterium to hydrogen ratio also matches ancient eucrite chondrites, which originate from the asteroid Vesta in the outer asteroid belt. [ 45 ]