Interlude: An ode to H₂O
Be water, my friend.
❝ Yes, water can flow and it can crash.❞
Water is a chemical compound with the chemical formula H₂O: a water molecule contains two hydrogen atoms connected to one oxygen atom by covalent bonds.
Water – like all matter – can exist as a liquid, a solid (ice) and a gas (water vapor or steam). Water also exists in a liquid crystalline state near hydrophilic surfaces [1,2].
"On Earth, 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds… and precipitation.
Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products."
– Wikipedia | Water
– http://www.flickr.com/photos/mommamia/2217623384
– http://www.flickr.com/photos/thk1304/8231240454
– https://en.wikipedia.org/wiki/Mammatus_cloud
"The surface of the earth is approximately 70.9% water and 29.1% land."
– CIA | The World Factbook
Water is vital for all known forms of life.
Water on Earth moves continually through the hydrological cycle of evaporation and transpiration, condensation, precipitation, and runoff, usually reaching the sea.
Some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A report suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.
❝ But it can become much more than a teapot or a bottle or a cup.❞
Much of the water found in the universe is a byproduct of star formation.
When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow eventually impacts on surrounding gas, the shock waves that are created compress and heat the gas: the water we see is formed in these warm, dense conditions.
On 22 July 2011 a report described the discovery of a gigantic cloud of water vapor containing "140 trillion times more water than all of Earth's oceans combined" around a quasar located 12 billion light years from Earth. According to the researchers, the "discovery shows that water has been prevalent in the universe for nearly its entire existence".[3,4]
Water vapor is present in
Atmosphere of Mercury: 3.4%
Atmosphere of Venus: 0.002%
Earth's atmosphere: ~0.40% over full atmosphere, typically 1–4% at surface
Atmosphere of Mars: 0.03%
Atmosphere of Jupiter: 0.0004%
Atmosphere of Saturn – in ices only
Enceladus (moon of Saturn): 91%
exoplanets known as HD 189733 b[23] and HD 209458 b.
Liquid water is present on
Earth: 71% of surface
Europa: 100 km deep subsurface ocean
Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus.
Water ice is present on
Earth – mainly as ice sheets
polar ice caps on Mars
Moon
Titan
Europa
Saturn's rings
Enceladus
Pluto and Charon
Comets and comet source populations (Kuiper belt and Oort cloud objects).
❝ Water can become a knife, gouging great valleys into the face of the Earth.❞
Water is important in many geological processes:
Groundwater is present in most rocks, and the pressure of this groundwater affects patterns of faulting.
Water in the Earth's mantle is responsible for the melt that produces volcanoes at subduction zones.
On the surface of the Earth, water is important in weathering processes such as erosion.
Water and, to a lesser but still significant extent, ice, are also responsible for a large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks, which make up the geologic record of Earth history.
❝ Water can also be a builder, each drop carefully depositing a microscopic layer of calcium carbonate upon another, creating stalactites and stalagmites over millennia.❞
Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology. And then there's speleology.
❝ Water sustains all life and life as we know it could not be without water.❞
This rings perhaps most true for the troglobites, which are among the things that speleologists study.
– By brian.gratwicke
Water has many distinct properties that are critical for the proliferation of life: it carries out this role by allowing organic compounds to react in ways that ultimately allow replication of genetic information.
The earliest life forms appeared in water…
Nearly all fish live exclusively in water, and there are many types of marine mammals. Some kinds of animals, such as amphibians, spend portions of their lives in water and portions on land.
Since invertebrate life evolved in an aquatic habitat, most invertebrates have little or no specialised adaptations for respiration (breathing) in water. Invertebrates do, however, exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes (see insect and mollusc siphons) and gills (Carcinus).
However, aquatic vertebrates must obtain oxygen to survive, and they do so in various ways: fish have gills instead of lungs (although some species of fish, such as the lungfish, have both); marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Some amphibians are able to absorb oxygen through their skin.
Plants grow in the water and are the basis for some underwater ecosystems; plankton is generally the foundation of the ocean food chain.
Water is fundamental to photosynthesis and respiration.
Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO₂ (absorbed from air or water) to form glucose and release oxygen.
All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO₂ in the process (cellular respiration).
Water is vital both as a solvent in which many cellular solutes dissolve and as an essential part of many metabolic processes within the organism.
Metabolism is the sum total of anabolism and catabolism: in anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information); in catabolism, water is used to break down bonds (releasing energy) in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes).
Without water, these particular processes – and life as we know it – could not exist.
Water is also central to acid-base neutrality, which has important implications in both organic and inorganic chemistry.
An acid – in other words, a hydrogen ion (also written H+, a single proton) donor – can be neutralized by a base – a proton acceptor such as hydroxide ion (OH−) – to form water.
Water is considered to be neutral, having a pH (the negative log of the hydrogen ion concentration) of 7: acids have pH values less than 7; while bases have values greater than 7.
❝ So be water, my friend.❞
By Andrea Fallas, PhD
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