Water

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Water is a ubiquitous chemical substance, composed of hydrogen and oxygen, that is essential for the survival of many known forms of life. In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth's surface. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within biological bodies and manufactured products. Other water is trapped in ice caps, glaciers, aquifers, or in lakes, sometimes providing fresh water for life on land.

Water moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea. Over land, evaporation and transpiration contribute to the precipitation over land.

Clean, fresh drinking water is essential to human and other lifeforms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world. There is a clear correlation between access to safe water and GDP per capita. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70 percent of freshwater is consumed by agriculture.

For more information about Water, read the full article at Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.

News tagged with liquid water

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More Evidence for a Revolutionary Theory of Water

Physics / General Physics

Jun 30, 2008 | 4.4 / 5 (149) | 14

The traditional picture of how liquid water behaves on a molecular level is wrong, according to new experimental evidence collected by a collaboration of researchers from the Department of Energy's Stanford ...

Jupiter's Moon Europa Has Enough Oxygen For Life

Space & Earth / Earth Sciences

Oct 16, 2009 | 4.8 / 5 (95) | 42

New research suggests that there is plenty of oxygen available in the subsurface ocean of Europa to support oxygen-based metabolic processes for life similar to that on Earth. In fact, there may be enough ...

Reconnaissance Orbiter Reveals Details of a Wetter Mars

Space & Earth / Space Exploration

Oct 28, 2008 | 4.3 / 5 (39) | 18

(PhysOrg.com) -- NASA's Mars Reconnaissance Orbiter has observed a new category of minerals spread across large regions of Mars. This discovery suggests that liquid water remained on the planet's surface a ...

Why Does Water Expand When it Cools? A New Explanation

Physics / Condensed Matter

Jul 17, 2009 | 4.2 / 5 (39) | 16

(PhysOrg.com) -- Most of us, when we take our first science classes, learn that when things cool down, they shrink. (When they heat up, we learn, they usually expand.) However, water seems to be the exception ...

Liquid saltwater is likely present on Mars, new analysis shows

Space & Earth / Space Exploration

Mar 17, 2009 | 4.7 / 5 (18) | 6

(PhysOrg.com) -- Salty, liquid water has been detected on a leg of the Mars Phoenix Lander and therefore could be present at other locations on the planet, according to analysis by a group of mission scientists ...

Evidence for ocean on Enceladus: Tiny Saturn Moon Could Be Targeted in Search for Extraterrestrial Life

Space & Earth / Space Exploration

Jul 22, 2009 | 4.6 / 5 (16) | 8

(PhysOrg.com) -- Plumes spewing from a tiny moon of Saturn - a moon roughly the width of Arizona - are filled with molecules that suggest that the moon, Enceladus, is likely another place in the solar system ...

Will Kepler find habitable moons?

Space & Earth / Astronomy

Sep 03, 2009 | 5 / 5 (14) | 5

(PhysOrg.com) -- Since the launch of the NASA Kepler Mission earlier this year, astronomers have been keenly awaiting the first detection of an Earth-like planet around another star. Now, in an echo of science ...

Scientists Develop New Method to Find Alien Oceans, Earth-like Planets (w/Videos)

Space & Earth / Astronomy

May 26, 2009 | 4.9 / 5 (14) | 3

(PhysOrg.com) -- Since the early 1990s astronomers have discovered more than 300 planets orbiting stars other than our sun, nearly all of them gas giants like Jupiter. Powerful space telescopes, such as the ...

Valley networks on Mars formed during long period of episodic flooding

Space & Earth / Space Exploration

Sep 08, 2008 | 4.6 / 5 (14) | 1

(PhysOrg.com) -- A new study suggests that ancient features on the surface of Mars called valley networks were carved by recurrent floods during a long period when the martian climate may have been much like ...

Scientists Observe Liquid Water Below Freezing

Chemistry / Materials Science

Jun 24, 2009 | 4.2 / 5 (14) | 8

(PhysOrg.com) -- Below 0 °C, water turns to ice. But beyond that, or below about -75 °C, the ice may turn back into liquid water. While scientists have previously predicted this phase transition with computer ...

A Tale of Planetary Woe (w/ Video)

Space & Earth / Space Exploration

Nov 11, 2009 | 4.2 / 5 (11) | 5

Once upon a time — roughly four billion years ago — Mars was warm and wet, much like Earth. Liquid water flowed on the Martian surface in long rivers that emptied into shallow seas. A thick atmosphere blanketed ...

'Cold' Mars Could Have Harbored Liquid Water

Space & Earth / Space Exploration

Jun 01, 2009 | 4.3 / 5 (9) | 7

(PhysOrg.com) -- A new NASA study provides further evidence that Martian minerals dissolved in water could have kept that water from freezing, even on a cold, early Mars.

Kepler and the Search for Life in Our Galaxy

Space & Earth / Astronomy

Sep 15, 2009 | 4.3 / 5 (9) | 1

(PhysOrg.com) -- There are so many stars in our galaxy that even if planets with complex life (animals and plants) are rare - say one for every billion stars - there could still be dozens here in the Milky ...

Model Suggests Origins of Mars Gullies

Space & Earth / Earth Sciences

Feb 09, 2009 | 4.6 / 5 (8) | 4

University of Arkansas researchers have used chemistry and geology to create a model that may explain the mystery of how modern-day gullies form on the surface of Mars.