We have given our planet the wrong name Planet 'Earth' - it should be Planet 'Water'.
Our solar system, and the universe, are full of 'Earth' planets. There's lots of dirt and rocks out there, but planets covered in liquid water, especially in large oceans are relatively rare. Our special home, 'Planet Water' is truly unique in our solar system with liquid water covering 70% of its surface.
Another key point is that water is absolutely essential for Life as we know it. The life on our planet is carbon based, but without liquid water there would be no life here. 'Water is the Hub of life' on Planet Water and our lives and the future of all life on our planet depends on water.
"Water is the Hub of Life. Water is life's mater and matrix, its mother and medium. Water is a most extraordinary and unique substance! Nearly all its properties are strange, which enabled life to use these properties as building blocks for its vital machinery. Life makes water dance in tune with the solids." Adapted from Albert Szent-Gyorgyi (1972)
There are some key points about the link between water and life
Originally the atmosphere was perhaps 50-70% carbon dioxide and oxygen was essentially absent. Chemical processes pulled the CO2 levels down to about 5% and the plants eventually pulled it down to about 0.04% that it is today. Importantly the plants also build the oxygen levels to the 21% today, otherwise we could not exist. The water cycle in life is completed when animals and plants respire. The energy built into organic molecules is released by special pathways that break the organic structure and uniting H an O into water again. This is how we get the energy to live and do the things we do. The energy of the sun is used to split the H2O molecule into H and O, it is stored in organic molecules - just like in a battery, and our cells can get the energy stored by combining the H and O back into water.
Life is a revolt against natural processes. The dominant feature of inanimate nature is that it naturally moves towards an equilibrium which has maximum disorder (decays to dust), that is to a state of maximum entropy (i.e. maximum disorder) and with little or no of free energy. Life bucks the trend of natural processes in the Universe. The main feature of life is that it tends to build and maintain order and structure. In other words, life acts to decrease its entropy, to fight the forces of decay. Life also acts to increase its free energy. Increasing entropy means tending to a state of complete randomness. Life has order, a pattern, and structure which it must work at to sustain and prevent decay. When we die we quickly decay - from dust to dust. Maintaining this structure and order requires energy, which ultimately comes from plants using solar energy to split the water molecule which is the opposite of entropy. Living organisms work hard to avoid decay by eating, drinking, breathing and breaking down organic molecules combining H with O to form water. Thus a living organism fights to increase its entropy - i.e. produces positive entropy - to avoid decay and death. Living organisms can only stay alive, by constantly consuming or extracting the negative entropy built into the structure of organic molecules by plants. Plants using solar energy to sustain themselves when the sun is shining.
What an organism consumes to stay alive is negative entropy. We are heterotrophs- living organisms that can not make their own food and survive by consuming complex organic substances for nutrition. Thus us heterotrophs devour negative entropy by utilising the potential energy built into the complex structure of organic molecules by the auotrophs, such as plants that use solar energy to create structure in organic molecules such as sugar, that are a type of organic battery. Autotrophs are organisms that can make their own food from inorganic substances, using chemical or solar energy. Certain bacteria, algae and green plants are autotrophs. Plants also burn organic molecules at night to sustain themselves when they cannot get energy from the sun.