We all think that water has always been here on Earth. No, it’s not true. Water was brought to Earth from space before the arrival of living organisms. Planetary scientists now have evidence to conclude that asteroids were the main source of Earth’s water while comets contributed a mere 10 per cent.
Why do we drink water? The answer is we feel thirsty. We are thirsty because we are dehydrated. Dehydration means we are losing more water than we consume. How do we know we are dehydrated? There is a thirst centre in the hypothalamus of our brain that gives the signal.
Water is essential for life because life needs a solvent as a medium in which all the body chemicals dissolve and chemical reactions can take place. There is no liquid better than water.
Water is very important because each molecule of water has a magnetic property ie one end of the molecule behaves like a weak magnetic north pole and the other end as the weak magnetic south pole. Other molecules have the same properties.
We know that opposite poles of magnets attract each other (+/ -). This polarity causes not only the water molecules but molecules of chemicals dissolved in this water to line up in certain ways, determining the shape of the aminoacid molecules that are vital for life.
The 20 aminoacids are the building blocks of proteins used in every cell in our body, making up three fourths of our body.
Another strange property of water is that solid water ie ice floats in water because the solid water is less dense than liquid water. When water freezes its molecules line up to form a very open crystalline structure, in which the molecules are arranged farther apart than they were in liquid water.
In other substances, the molecules are closer together in the solid form and thus it is denser than in the liquid form. During the Ice Age, ice formed a skin on top of the ocean at high latitude, keeping the water underneath at a warmer temperature.
If the ice sank to the bottom of the sea the top layer of the uncovered water would in turn freeze. If the process repeated the whole ocean would have been a large solid ball of ice.
So, as far as we know life needs the presence of liquid water. In terms of solvent power, ammonia is the next best, but it lacks many properties of water and is not essential for life.
Scientists believe that water facilitated the formation of the planet’s first life forms – acting as a medium in which organic compounds could mix with one another (primordial soup) and possibly protecting them from the sun’s radiation.
During the process of evolution from simple one-celled organisms to the most complex plants and animals, water has played a critical role in survival technique.
In humans water acts as a solvent and a delivery mechanism, dissolving essential vitamins and nutrients from food and delivering them to cells. Our bodies also use water to flush out toxins through urine and faeces. It regulates body temperature by sweating and aids our metabolism by the digestive juices secreted internally and by hormones.
Water has also promoted human life in other ways, by providing fish and aquatic vegetables for food. It has helped in the advancement of civilisation, taking people and animals from one part of the world to the other by boat.
Water can exist as vapour to provide humidity. It can be stored in the atmosphere as clouds and be delivered as rain across the planet to help vegetations grow. The vast oceans serve as home for a variety of marine life.
The beautiful Siroi lily in the mountain ranges of Ukhrul or the colourful lotuses in the Loktak Lake at Moirang in Manipur would not have grown without water.
While we know that water is vital for life on this Earth, scientists have wondered if life is at all possible without water but with some other fluid medium, on other planets.
What else is there apart from water? Scientists have come up with ammonia and formaldehyde, being the most eligible liquids. But there are problems with them.
Liquid ammonia only exists at extremely cold temperatures, at which organisms would not have energy (heat) for their metabolism. Formaldehyde on the other hand, remains liquid at a larger range of temperatures than water and is capable of dissolving many organic materials. But scientists have found no evidence that it can support life. Indeed it is poisonous to the present life forms.
However, new research by George Cody along with Conel Alexander and Larry Nittler from Carnegie Institute for Science, USA, suggests that formaldehyde may have helped in the primitive solar system to create the organic compounds present in the universe that gave rise to life.
Another recent study suggests that an alternative life form might be lurking in our solar system. Researchers studying Titan – a ‘moon’ orbiting Saturn, noticed that hydrogen in the moon’s atmosphere was not found on its surface. One explanation for the missing hydrogen is that life forms are consuming it, just as we consume oxygen.
Water makes up 60 percent of our body and it needs replacement everyday. Nobody survives without water for more than a few days but one can survive without food.
Scientists have been debating how much water a person needs everyday. To some extent, it depends on age, size, level of physical exercise and the existing climate.
Recent studies have revealed that there is no set daily requirement of water but the Rule of thumb is that you should drink when you are thirsty (dehydrated). If your urine is white or slightly yellow, it is a good indication that you are hydrated.
However, there have been some calculations since I was a medical student that an average person should drink 1.2 litres of water every day to complement the 2 litres of water we get from food. To put it in another way, one should drink 8 glasses of water every day (each glass = 8oz).
Based on the belief that life will exist where there is water, the search for water on other planetary bodies has taken a giant leap forward in recent months. In November 2011, NASA announced that it had found substantial quantities of water on the Moon. A month later, the Cassini spacecraft obtained data about one of Saturn’s moons, Enceladus, that may confirm the presence of sub-surface liquid water on the Moon.
Until recently, scientists were puzzled that water could survive in liquid or vapour form in the ‘disc of materials’ from which the planets formed (theory of gravitational collapse of giant molecular cloud). They have explained that there is plenty of hydrogen in the “clouds” produced by the Big Bang from which stars formed. Hydrogen combines with all the available oxygen to convert it to water (H20).
In the stratosphere of Earth the ultraviolet radiations from the sun are constantly converting oxygen molecules (O2) into ozone (03), but other chemical reactions convert the ozone to oxygen as fast as it is formed. There is thus a permanent layer of ozone high over our heads, which filters most of the ultraviolet radiation coming to us.
Likewise, within the “cloud of materials” from which planets started to form, there is a similar shielding effect. This allows complex and even more complex molecules to exist from their interactions. They provide a rich source of organic compounds with which planets can be seeded with life.
But the question is how water and complex organic molecules got down to earth after the planet had cooled off sufficiently to stop the water boiling away. Scientists say that they came from small planets, which always contained water, and never got hot enough for the water to vaporise.
When Earth was young, Jupiter is in the right place to have sent to it just enough asteroids rich in water. The earth contains less than 1 per cent water but the debris in the Asteroid belt, which is the region of the solar system, located between the orbits of the planets Mars and Jupiter contains 10 per cent water.
Findings of the proportion of water in meteorite samples that have fallen on earth confirm that Earth acquired its volatile materials from impacts at a late stage of the formation of the planet. The recent discovery of water locked up in moon rocks also confirms the hypothesis.
Because Earth did form along with a large moon, and it did have oceans of liquid water, life could get started on this planet. But we are still waiting for the scientific evidence of how life first came about on Earth and subsequently evolved into the intelligent humans we are now. The evidence will come one day, I am sure.
Nov 28 2011