How and where was water first created?
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Herman D鈥橦ondt Sydney, New South Wales, Australia
Water was first created in deep space, after hydrogen and oxygen first formed. All hydrogen atoms were created about 380,000 years after the big bang. Oxygen was created much later in the nuclear furnaces of stars, towards the end of their life cycles.
Stellar lives begin by converting hydrogen into helium. Then, as the hydrogen starts to run out, helium is converted into progressively heavier elements, including oxygen, all the way up to iron. Later, these elements are ejected from the stars.
In smaller stars, elements are released when the star goes through its red giant stage. In very heavy stars, this happens when the star explodes as a supernova.
When atoms of elements collide into each other in space, they can form compounds, such as water. To make water, one atom of hydrogen and one oxygen atom combine to form a hydroxyl ion. The hydroxyl ion can combine with a second hydrogen atom, forming a stable molecule that doesn鈥檛 react further. This takes a very long time, as atoms are highly spread out in space.
Currently, there are two ideas explaining how water eventually reached our planet. The first is that, when Earth formed as a red-hot fireball, it managed to hold on to some of the water that was present in the cloud of gas and dust that formed the solar system. The second says that most of the water was delivered after Earth cooled down and the planet was bombarded with asteroids and comets, the latter of which are sometimes called 鈥渄irty ice balls鈥�.
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Eric Kvaalen Les Essarts-le-Roi, France
Water first formed after oxygen appeared in the universe, and oxygen is created along with certain other elements by stars after they finish burning hydrogen. This would have been a couple hundred million years after the universe was born.
The earliest evidence of water in our universe is a cloud containing water vapour that is 12 billion light years away. In other words, water existed 1.8 billion years after the big bang
While water initially manifested in space as a vapour, it can also form small ice crystals out in space. Liquid water would only have existed after the creation of planets that had the right temperature and pressure.
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Mike Follows Sutton Coldfield, West Midlands, UK
suggests that water may have been first created less than 1 billion years after the big bang. , which were nurseries for the second generation of stars.
The big bang created hydrogen, helium and a tiny bit of lithium and beryllium. Heavier elements, including oxygen, are forged inside stars and would have been much less abundant when the universe was only about 7 per cent of its current age. The relative scarcity of oxygen would have limited the speed of the chemical reactions that produced water, though the high density and temperature of the molecular gas clouds in which the reactions were taking place would have helped.
Most of the water in the universe is now created by reactions on the surface of interstellar grains of dust. In the early universe, there will have been much less dust in the interstellar medium because fewer dust-producing supernova explosions had occurred by then. In the absence of dust, a reaction between a hydrogen atom and an oxygen atom produces a hydroxyl molecule, which then reacts with another hydrogen atom to produce water.
We have yet to discover a better solvent than water for biochemical reactions, and the fact that it has probably been present throughout the universe for almost 13 billion years significantly increases the possibility of extraterrestrial life.
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