Life - what is it made of?
Water - the key factor

The key constituent to the life process is something to act as a transportation and suspension medium, to allow chemical processes to physically occur.  Liquids and gases are the obvious candidates for this.  Gas though, has the disadvantage that it allows heavier molecules to settle out through the simple effects of gravity. This effectively takes essential life-forming molecules out of play.   We may well have found this on Jupiter, for no organic molecules were detected by the Galileo probe, when it plunged into Jupiter's atmosphere a few years ago.

(ABOVE) Jupiter, with the moon Io passing across its face.
Voyager 2 image.  © NASA

The energy levels - ie wind, that are required to remix settled-out molecules into a solution, are so severe that they are likely to destroy the structure of any potential living entity that might be forming.  Liquid suspensions, too, can suffer the effects of gravity; however the remixing energies, such as convection and evaporation, are gentle.  It is therefore far more likely that life will occur in a liquid environment, or at least in an environment where liquids are relatively abundant.

The most obvious candidate as a liquid medium is water.  It is the universal solvent.   Many substances can go into solution in water and this aids chemical processes in several ways.  It speeds them up, allowing new chemical units to be brought into contact with one another, and it transports away the results of the process - be it life itself, or the waste products from life processes.  Water is ideal for this.  Like carbon, it is universally abundant, and its unique ability in bond-forming allows it to do some very helpful things for life processes.

The reason it is such a good solvent is due to its structure and internal atomic bonding.   As you will know, it is made up of two hydrogen and one oxygen atom.  The hydrogen atoms each have a single electron, while the oxygen has eight electrons.  But the oxygen nucleus exerts a much stronger attraction to electrons than does the hydrogen's.  Even the hydrogen electrons are attracted towards the oxygen end of the molecule.  This causes a charge imbalance within the water molecule.  The oxygen end consequently has a negative bias as the electrons, which carry negative charge, spend most of their time in this area.  The hydrogen end, which is deprived of electrons, consequently possesses positive charge.  Thus, the water molecule is electrically polar in nature.

If a similarly-polar soluble material is now added to the water, any free negative ends of that solute will link weakly with the hydrogen atoms of the water, thus putting the solute into solution.  Those bonds are easily broken too, by evaporation or other processes.  So a ready, two-way reaction can take place, allowing the materials of life to be moved around and worked with.

You will note that silicon-dioxide - sand, unlike carbon-dioxide, is not soluble in water and is largely inert in the presence of most chemicals. 

It does not constitute a good medium in life processes, which is another reason for ruling out silicon as a basis for life.

So what is the best base element for life?

The Importance of Carbon

The cell
Life: What Exactly Is It?- Discussion with Dr Stanley Miller

Life in the Universe

Nasa - Origins Investigation 13 Characterize the traits of the universal common

NASA Research Findings Space Science Workshop 1996

Evolution and the Origins of life

From Primordial Soup to the Prebiotic Beach

Teachers Wormhole



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