Why Water Is Necessary For Life To Exist In The Universe

Earth is the only planet that we know of that currently has life on it in the observable universe. The other planets in our solar system have not shown any indication of life on them based on our understanding of it. Even the hundreds of earth like planets discovered in other star systems have not shown any tell tale signatures of life on them. That is, water must be present in order for life to exist here and probably everywhere else in the universe with one critical criterion, it must exist as a liquid or no activity of life will engender in a dry or even frozen environment. Water plays a critical role in life since in just about every biochemical reaction that takes place in a living organism depends on it to produce all the necessary ingredients to sustain it. There is no other substance or molecule in the universe capable of interacting with as many of the elements in the periodic table as water to produce hundreds or even thousands of chemicals for life to exist.

It Exist Simultaneously in Three States

Let us look at water from a chemical perspective. Water is a relatively simple substance composed of two hydrogen atoms and one oxygen atom, thus the shorthand chemical name H₂O. On earth water, which covers about 71% of the Earth’s surface, exists simultaneously in all three forms as a liquid, a solid (ice) and a gas (water vapors). It is this characteristic of water under the physical conditions on Earth that make the existence of life possible here. If water cannot exist in these three states at the same time on a planet life cannot exist. That means the planet is not in a habitable zone for life. It is the only substance that exists naturally in all three states. Water has been found on many of the planets in our solar system but not in all three states simultaneously.

For example, water vapors have been found on Mercury, Venus, Mars, Jupiter and Saturn but not as a liquid on any of these planets. Also none of these planets are in the so-called “Goldilocks Zone” to be habitable for life. Ice has been found on Mars; the moons of Jupiter and Saturn and even on our own Moon, but again these are all inhabitable places for life. Water has even been detected in interstellar space and on some of the recently discovered exoplanets but the water there probably does not exist in the three states simultaneously to support life. In some cases the atmospheric pressure on some of these planets are so great that water only exist as ice no matter how warm it is on the planet.

It Has A High Specific Heat Capacity

I know some of you are probably wondering how we are able to detect water so far away from Earth. It is simple. Water is a strong absorber of ultraviolet, microwave and infrared (heat) light due to the vibration of the hydrogen-oxygen bonds. This is why food get hot in a microwave oven because the water molecules are absorbing the microwave which causes an increase in the vibration of the atoms, thus producing heat. This physical chemical property of water is another characteristic that makes life possible here. When water is heated it does a very good job of holding that heat because it has the second highest specific heat capacity (the ability to hold heat) of all the substances known. This property gives water the ability to moderate the earth’s climate to make it possible for life here.

Almost Everything Dissolves In It

The property of water that really set it off from the rest of the substances on Earth that makes life possible is its ability to dissolve just about anything such as salts, acids, bases, sugars, and gases. It also dissolves proteins and DNA the main components of organisms on earth. In light of this a new bacteria capable of utilizing Arsenic was recently found, guess where, at the bottom of a lake. The only way that bacterium can use the Arsenic was because it is soluble in water.

Strong Surface Tension

Finally, water has a strong surface tension, the ability to stick to surfaces and be elastic at the same time. This property makes it possible for plants to draw water through its roots and makes it possible for blood to circulate through our body. 

If there is life on other planets out there it probably started the same way life started on Earth in the water. The life forms on other planets probably went through some form of development from something simple to something more complex just as it happened here due to chemical interactions of molecules present in the water. All 118 elements we have discovered in the periodic table also exist everywhere in the universe and they would follow the same physical and chemical laws since all the elements originated from the stars.

The processes of life on earth are controlled by a relative few core elements in the periodic table, namely; Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous and Sulfur (The Big Six or CHNOPS) with trace amounts of other elements. These elements make up the main components of an organism; the nucleic acids in DNA, proteins, and lipids (fatty substances). Most likely organisms in other parts of the universe are probably made up of the same main elements as the organisms are on Earth with a few minor exceptions. For example, the recent discovery of bacteria in Mono Lake in California contains Arsenic instead of Phosphorous as one of their core elements. Obviously, based on these facts, scientists are not expecting to found another organism on some distant planet using Plutonium in their system as one of the core elements to live because it only reacts with a relatively few elements. The resultant compounds do not seems to be of any use biologically.

Now all this bring us to the inescapable conclusion that water must be present in order for chemical reactions to take place for an organism to develop and move forward to a more complex life form. We know all biological processes in organisms on Earth take place in an aqueous environment and the reason that happen because water plays a crucial role in most of these biochemical reactions for processes such as reproduction, cell division, and metabolism to take place. There is no other substance besides water that these reactions can occur in since many biological chemicals are soluble in water. So most likely biological processes in other parts of the universe must also occur in an aqueous environment and the processes out there on other planets must involve the same basic six elements used here. For example, there are not too many gaseous molecules we can breathe in such as oxygen to add to an equation to extract energy in our system and breathe out the by-product as the harmless gas carbon dioxide. Carbon and Oxygen have a unique ability to combine with many elements, especially Hydrogen, in different combinations to cause a lot of these biological reactions in the organism. Another example, photosynthesis will not be possible if the chlorophylls in plants could not combine Carbon, Hydrogen, and Oxygen with a photon of light from the Sun to produce energy and food for plants. There is no other combination of elements in the periodic table that can replicate this very important chemical reaction in plants.

Water is obviously the main ingredient for life to exist here and probably anywhere in the universe, but it must exist in all three forms on a planet in a habitable zone in order for it to work. If the planet is too hot there will be no water in the liquid state for any chemical reactions to take place to support life. The molecules will never come to together to create life and eventually evolve into a more complex organism. Also the organism may not survive the extreme heat since water broils at certain temperature depending on the atmospheric pressure. On the other hand, if the planet is too cold the water would exist as ice. No chemical reactions will occur since the necessary elements will never come together to support life. If you look at this another way, we and other organisms on this planet survives because water has a wide temperature range as a liquid, that is, from 0°C (32°F) to 100°C (212°F). If for some reason the Earth was moved out of the habitable zone to temperatures outside this range we will not survive very long simply because water does not exist in the liquid state outside of this range.

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