Introduction

Origin of life is one of the greatest challenges of scientists, which still remains as an unresolved mystery. There are different ways of research but the convincing facts are few. Astrobiology deals with the study of life on earth and beyond earth. Researches are in progress to investigate the origin and evolution of life on earth and the possibility of life elsewhere in the universe.

Recently, astrobiologists have discovered a ‘ghost particle‘ from outer space that points to the existence of alien life. The researchers from the University of Sheffield and the University of Buckingham Centre for Astrobiology have discovered this ‘living balloon’ from the stratosphere, at 27 km above the earth’s atmosphere, which was  found and collected by balloons sent for examining space debris. The researchers said that this ‘ghost particle’ is a living balloon which an alien microscopic organism might inflate with lighter than air gasses allowing it to float in the air or the seas of an unknown space environment. It shows that DNA and viruses can travel through space from planet to planet, surviving all severe situations. This discovery may give some clues to our age-long query of where life on earth came from, with a possibility to point our finger to the space. But, the path towards realty is harder, and we have to wait for more explanations and solid proof.

In spite of the existence of millions of stars and their planets in the universe, we know, with our limited knowledge, that earth is the only planet where life, nay intelligent life, exists. But, what are the reasons that distinguish earth from other planets and make it most suitable to harbour life?

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Earth – the Blessed Planet

Unlike other planets, our earth is a beautiful place with its blue oceans, green nature, huge mountains, rivers, lakes, streams, deserts, land masses and above all the vibrating spell of life. Life is found everywhere, from the coldest regions of poles to the hottest zones of the equator, and from the bottom of the deep oceans to the top of the atmosphere. And the life is amazingly diverse consisting about 14 million species.

With 8000 miles in diameter, earth is the fifth largest planet in the solar system. The different seasons in earth occur due to its rotation with its axis tilted at 23.45 degrees with respect to the plane of earth’s orbit. If the angle of tilt had been changed, or if the earth rotated at slower speed, the whole life would have finished by over-heating or over-freezing. Earth travels around the sun through its 292 million mile orbit in 365 days, 5 hour, 48 minutes and 45.51 seconds with an accuracy of thousandth of a second. If it travelled too fast or slightly slower than this speed the whole life would perish.

Atmosphere – the Protector

The atmosphere near the surface consists of nitrogen (78%), oxygen (21%) and other ingredients (1%). The content of gases in the atmosphere, in a non-polluted situation of the humans, is the best suitable for life. Oxygen makes the atmosphere breathable. Plants absorb carbon dioxide during photosynthesis and enhance life by producing oxygen and food. The oxygen molecules in the atmosphere interact with solar radiation and form a protective ozone layer in the upper atmosphere. The ozone layer absorbs harmful ultraviolet radiation from the sun and protects the living beings on earth.

Carbon dioxide content in a non-polluted atmosphere is ideal for life. Too much carbon dioxide, due to air pollution created by our negligence, will be poisonous and too little will cause a freeze death due to inability to trap heat from sun. The atmosphere influences the climate and protects us from the mishap of meteors.

Air near the surface of the earth maintains a suitable temperature that enables life to exist. The temperature on earth never goes from one extreme to the other. Warm air moves upward from the surface of the earth creating wind current that is essential for the ecological balance of the earth. The carbon dioxide and oxygen content are always balanced as per the requirement for a healthy life.

Sun – the Energy Provider

The sun gives us light and life. The sun is the main reason for existing life on earth and if there was no sun, nobody can survive on earth. Even though all planets receive light from sun, only earth utilizes it most effectively. Sun is essential for growth of all living beings including plants. Through photosynthesis trees and plants produce oxygen and food. The sun delivers more than 130 trillion horse power of energy to earth every day. Out of the total solar incoming energy, 23 percent is absorbed by the ozone, water vapour and dust particle in the earth atmosphere and 48 percent is absorbed by the earth surface. The balance 29 percent is reflected back to the clouds. Being located at an ideal distance from the sun, earth receives heat and light at the right amount and right time that support life.

Moon – the Supporter

Unlike the moons of other planets, our moon is sufficiently larger in size compared to the size of earth, which helps to minimize the tilt of earth’s axis. A change in tilt of earth’s axis from its 23.45 degrees will result in extreme season changes that will make life difficult. Moon is at right distance from earth and is of right size; otherwise the tides produced due to moon would have overflown onto low land areas and worn away mountains.

Water – the Lap of Life

Water is the most essential thing without which we cannot think about life. Earth is the only planet we know with huge amount of water. Almost 70 percent of the surface of earth is covered with oceans with an average depth of about 4 kilometers. Water vapor present in the atmosphere is responsible for the weather condition.

Our survival is largely dependent on the oceans of the earth. Water stabilizes the day and night temperature of earth properly. Water absorbs heat from the earth surface and keeps it fairly cool during the day time. At night, the ocean releases heat and keeps the earth surface from getting too cold.

Water can be seen in three different states: frozen as ice, liquid form in oceans, rivers, etc., and vapour form in atmosphere. Water in ice form, will float near the surface, unlike any other liquid, and will get melted during summer due to the heat from the sun and the warm water below it. Floating of ice prevents the water below it from freezing further. On the other hand, if it sunk when frozen, the process will repeat and the whole water will become ice, making the chemical processes behind life impossible. Warmer water above 4 degrees will sink to the bottom and will warm the bottom of the oceans, thus producing ocean currents that keep the ocean water in liquid form.

Habitable Zone

Unlike Mars and Venus, earth is lying within the sun’s habitable zone, meaning it is in an orbital region that can possess liquid water on its surface and support life. If the earth’s orbit had been just a little bit different from its present position, there would have been no life here.

Magnetic Field

Due to earth’s rotation and its molten nickel-iron core, a magnetic field is produced. This magnetic field protects the earth from the storm of charged particles from the Sun; otherwise violent radiations would have wiped off life from earth in its delicate stages.

Conclusion

As per fossil evidence, it is believed that life might have started on earth about 3.5 to 4 billion years ago. But we do not know how the DNA molecules were formed in the beginning. It might have happened by chance by the arrangement of some of the atoms of the elements present in the earth or it might have come to earth from elsewhere, from the infinite realm of universe. We do not know. The favourable conditions on earth might have accelerated the development of life starting from the replication of DNA, natural selection and through the subsequent processes of evolution; and have now evolved to become an intelligent man capable of questioning about the origin of life.

Due to a rare combination of favourable factors, earth has become a unique planet in the solar system to host life of all forms, starting from the single celled micro-organism to the intelligent human being. However, possibilities cannot be ruled out about the existence of intelligent alien life on some other planets, encircling any other stars, having similar or better conditions that favour life. Let us hope that time is not too far off for such an exceptional moment of meeting of two distinct forms of life:…..the human intelligence on one side and the extra-terrestrial intelligence on the other side..?! 

Image Source: http://commons.wikimedia.org/wiki/File:Earth_Eastern_Hemisphere.jpg


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