Water is very important to us, since without it, there would be no life on earth. We had scientists lined up to answer this one. One theory that they didn't mention is that water came from comets hitting the early earth. We give you two complete answers, both correct of course.

ANSWER by Mark B.:

Tough question! The origin of water dates back to the formation of the earth, therefore the answer lies in the early history of our atmosphere. I found such a history in the children's reference section of the Carlingwood Library. The World Book Encyclopedia of Science, The Planet Earth volume, under the section The Earths's Atmosphere and Climate, theorizes on the origin of the atmosphere, (which includes water vapour.)

Soon after the Earths formation (about 4.5 billion years ago) the Earth may have resembled present day gas giants (Jupiter, Saturn, Uranus, Neptune), with a thick layer of gases surrounding a very dense core. In the earths past most of this original cosmic atmosphere was lost, possibly having been burnt off during a period of intense solar activity. (this is suspected because only trace amounts cosmic gases, neon, xenon for example are found in today's atmosphere.) Whatever the case was, a second atmosphere developed, coming from the Earth itself. For many millions of years after its formation the Earth's surface was molten, even after a thin crust formed there were incessant volcanoes. During these years of great activity the rocks gave off large quantities of gases, including; nitrogen, ammonia, carbon monoxide, methane, carbon dioxide and water vapour - a mixture given off by volcanoes and fumaroles today. As the Earth cooled and after the surface temperature had fallen below 100°C , (boiling point of water), water vapour in the atmosphere condensed (turned to liquid form) and fell as rain. The rain formed shallow lakes and created streams.

Today's modern atmosphere is 4% water vapour by volume and 3% by weight, still this only 0.001% of the total water supply. The rest is in liquid/ice form on the surface. This water covers 70% of the Earth's surface. Water vapour originates on the earths surface so its concentration decreases with height; it is completely absent beyond 12 kilometres above the Earths surface. Plants and animals also produce water vapour as a natural by-product of the metabolic process.

References: The World Book Encyclopedia of Science. Volume: The Planet Earth
Section: The Earths's Atmosphere and Climate

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Now our second scientist Gord Oderkirk, alias the professor.

{picture from compton's}

Usually, nature makes all the water we need by recycling. Water in streams, rivers, and lakes is used by living things such as animals and plants. Any water that animals drink but do not need ends up being "peed" back out as urine. The water in the urine then evaporates into the air. Water that the plants do not need evaporates through the leaves of the plant. Also, water evaporates from all the bodies of water in the world, including the oceans. All the water in the air collects together to form water droplets. The water droplets collect together to form clouds. When the water droplets get big enough, they fall to the ground as rain and form streams, rivers, and lakes.

Water can be formed in some other ways, as well. For example, water is formed every time gasoline or wood is burned. Of course, you cannot see the water vapour and all sorts of other chemicals are also formed, such as carbon dioxide other pollutants.

It is also possible to "make" water by combining hydrogen and oxygen, H2O, since these are the two chemicals that make up water. This would require a lot of energy, however, and would be very expensive to do.

And I always thought water came from the tap! Thanks for your questions.