From where did the water came on Earth?

Origin of Water on Earth

by

Dr. Nitish Priyadarshi

All life on Earth depends on water. Humans use water for many purposes like drinking, irrigation, fisheries, industrial processes, transportation, and waste disposal. Water is also an essential part of the geological cycle. Rain water converts the granitic rocks of the continents to clay, sand and solutes, and transports them to the ocean where they become the raw material of future continents. Approximately 80 percent of the water on the Earth is in the oceans, 19 percent is in the pores of rocks beneath the Earth’s surface, 1 percent in the form of ice, 0.002 percent is in the streams and lakes, and only about 0.0008 percent in the atmosphere.
Considering the central role of water in human affairs, it is remarkable how little we know about it.

The question of the origin of water on Earth, or more accurately put, the question of why there is clearly more water on the Earth than on the other planets of the Solar System, has not been clarified. There are various popular theories as to how the world's oceans were formed over the past 4.6 billion years. Some of the most likely contributing factors to the origin of the Earth’s oceans are as follows:

1. The cooling of the primoridal Earth to the point where the outgassed volatile components were held in an atmosphere of sufficient pressure for the stabilization and retention of liquid water.
Today, the air we breathe is stable mixture of 79 percent nitrogen, 20 percent oxygen, about 1 percent argon (or inert gas), and trace gases like carbon dioxide and water vapour. But our planet’s original atmosphere, several billion year ago, was far different. Earth’s very earliest atmosphere probably was swept into space by the solar wind, a vast stream of particles emitted by the Sun. as Earth slowly cooled, a more enduring atmosphere formed. The molten surface solidified into a crust, and gases that had been dissolved in the molten rock were gradually released, a process called outgassing. Outgassing continues today from hundreds of active volcanoes worldwide, thus, geologists hypothesize the Earth’s original atmosphere was made up of gases similar to those released in volcanic emissions today: water vapor, carbondioxide, nitrogen, and several trace gases.
As the planet continued to cool, the water vapor condensed to form clouds, and great rain commenced. At first, the water evaporated in the hot air before reaching the ground, or quickly boiled away upon contacting the surface, just like water sprayed on a hot grill. This accelerated the cooling of Earth’s crust. When the surface had cooled below water’s boiling point (100 degree c or 212 degree F), torrential rains slowly filled the low areas, forming the oceans.

2. Comets, trans-Neptunian objects or water-rich asteroids (protoplanets) from the outer reaches of the asteroid belt colliding with a pre-historic Earth may have brought water to the world's oceans. That the Earth's water originated purely from comets is implausible, as a result of measurements of the isotope ratios of hydrogen in the three comets Halley, Hyakutake and Hale-Bopp by researchers. According to this research the ratio of deuterium to protium (D/H ratio) of the comets is approximately double that of oceanic water.The Earth is believed to have formed hot and dry, meaning that its current water content must have been delivered after the planet cooled. Possible candidates for supplying this water are colliding comets and asteroids. Because of their large ice comet water has shown that comet water is significantly different from typical ocean water on Earth.
Asteroidal ice may give a better match to Earth's water, but until now, any ice that the asteroids may have once contained was thought to either be long gone or so deeply buried inside large asteroids as to be inaccessible for further analysis.

3. Gradual leakage of water stored in hydrous minerals (actinolite, borax, epsomite, serpentine, tremolite, gypsum etc.) of the Earth’s crust. The heating or metamorphism of minerals containing water results in the extraction of water. These are the water that have been trapped inside rocks for millions or billions of years. Loss of volatile constituents, H2O, CO2, and the like, are the dominant processes which occur when rocks change their pressure-temperature environment and undergo prograde metamorphism through tectonic processes.

4. Magma represents a fiery-liquid silicate melt, containing various elements, oxides and volatile components (fluorine, chlorine, water, carbon dioxide, etc.). Magma can be solidified in the depth of the Earth’s crust under the cover of the overlying rocks and at the surface or near the surface of the Earth. In the former case the process of solidification of magma is slow; it takes the whole of magma enough time to be crystallized. When there is a rapid uplift of the magma on to Earth’s surface its temperature becomes lower, the pressure drops down to normal, and volatile components are separated including water. Release of water to the atmosphere from the cooling of the magma is happening from millions of years.

Reference:

Drever, J.I. 1982. The Geochemistry of Natural Waters. Prentice-Hall, Englewood Cliffs, N.J.

Fyfe, W.S., Price, N.J., and Thompson, A.B., 1978. Fluids in the Earth’s crust. Elsevier Scientific Publishing company, New york.

Milovsky, A.V. and Kononov, O.V. 1985. Mineralogy. Mir Publishers, Moscow.

Tarbuck, E.J. and Lutgens, F.K. Earth Science. Prentice Hall, New Jersey.

http://en.wikipedia.org/wiki/Origin_of_the_world
http://www.ozh2o.com/h2solar.html
http://www.astrobio.net/news/article1905.html
http://scrapetv.com/News/News%20Pages/Science/Images/Asteroid-impact-on-Earth.jpg

Is Earth part of our solar system ?

Is Earth part of our solar system ?

Dr. Nitish Priyadarshi

From early age my mind always boggled at the mysteries of our solar system and the Sun. How they originated, how they are formed and how do they look . All these questions always puzzled me. Ideas about the formation of the Earth and our place in the universe often begin with star gazing. We ask more, and we learn more.
When I started studying geology I came to know that our mother earth is member of the solar system. All the principal theories which have been advanced to explain the origin of the earth, have in common the idea that the planets evolved from the sun. Regarding the origin of earth a number of theories have been put forward but none of them can be said to be perfectly correct.

The planets in our solar system comprises two sets. The inner terrestrial or rocky planets include, from sun out, moonlike Mercury, torrid Venus with its carbon dioxide green house and sulphuric acid clouds, Earth with cool blue seas and multicolored lands, ice capped Mars with long dry rivers and giant extinct volcanoes, and the frigid and commonly carbonaceous asteroids. The outer Jovian or ice-gassy planets are hydrogen-rich Jupiter with sulfurous plus a dozen icy satellites, gassy Saturn with its equally icy satellites and prominent rings, and the three less well known outermost planets.
How then, and when, did so diverse a collection of planets come to be as they are? Over the centuries that humankind has pondered such questions, different hypotheses have been advanced or modified.
It is commonly believed that the earth evolved with other members of the solar system . It means that earth and the other planets revolving round the Sun should have similarities in physical and chemical properties.
But to my great surprise the fact is opposite. When I went through the information about the other planets, I found out that there is a great difference between the earth and the other planets and Sun. There are some similarities between the other planets e.g. Saturn and Jupiter but our earth is totally different either in geology and geochemistry or in composition of gases from other planets.
Recently Pluto has been voted off the island. The distant, ice-covered world is no longer a true planet. According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit.
Pluto has been demoted because it does not dominate its neighborhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons.

If you closely view our solar system you will find that our earth looks totally different from other planets. As if it is a foreign member intruded in solar system or been trapped in between the solar system. Our Earth is full of life and water. Prominent gases are Nitrogen and oxygen. It is active planet. If you put these definitions on other planets the answer is totally opposite. If we consider about the new definition of the planet, other than it orbits the sun and is large enough to have become round due the force of its own gravity and dominate its neighborhood, earth has no other similarity with other planets.

Earth’s ocean and atmosphere have evolved throughout the history of the planet, and continue to change today. Their original source and composition are not yet clearly identified. Compositional characteristics, such as less than solar proportions of the inert gases neon, krypton, and xenon, indicate that our atmosphere did not develop directly from nebular gas.

• Major gases on the Sun, Jupiter, Saturn and Uranus are hydrogen and helium, Mercury has helium and carbon dioxide, Mars atmosphere is composed of carbon dioxide. Whereas Earth has 77% nitrogen and 21% oxygen with traces of carbon dioxide. If earth has been borne from the same source and at same time there must be similarities in composition of the gases, which is not here.
  


• Early speculation proposed that the Moon broke off from the Earth's crust because of centrifugal forces, leaving a basin – presumed to be the Pacific Ocean – behind as a scar. The prevailing hypothesis today is that the Earth–Moon system formed as a result of a giant impact. A Mars-sized body (labelled "Theia") is believed to have hit the proto-Earth, blasting sufficient material into orbit around the proto-Earth to form the Moon through accretion. But Moon is very much different as it has no atmosphere and no magnetic field as compared to earth. Also the density of the Moon is much less than that of the Earth indicating that the Moon has comparatively less Iron and Nickel than the Earth. Although the lunar rocks bear many similarities to rocks common on Earth, they differ on one basic point – they contain no water, no hydrated minerals, and no minerals with the OH group in their crystal structure . In contrast, minerals that are hydrated or contain the OH group are plentiful on Earth. So where did the Moon come from? There is no clear answer to this question, in spite of all explorations and analyses.
  


• There is no geological movements on the other planets as compared to earth were geological movements in the form of plate tectonics is prominent.
  


• Heavy noble gases (xenon, neon, Krypton) are rare on earth as compared to space and the sun.
  


• Even the intensity of the magnetic field from planet to planet varies dramatically. Again I will say if the all the planets have the same origin there must have some similarities in the strength of the magnetic field which is not here.
  


• It is commonly said that Venus is very similar to earth. But it is composed mostly of carbon dioxide compared to Earth which is mostly composed of nitrogen and oxygen with trace of carbon dioxide. Scientists say that there was probably a very much larger amount of carbon dioxide in the earth’s atmosphere when the earth was first formed, but it has since been almost all incorporated into carbonate rocks. Why this phenomenon happened only on Earth and not on Venus. Also Venus has no magnetic field. Venus’ sky is red because carbon dioxide scatters red light. The sun appears bluish because of loss of the red component. There is no liquid water on Venus and therefore no life. The rotation of Venus is slower than its revolution making the rotation of Venus retrograde. As a result, the atmospheric circulation is totally different from that on Earth.
  


• Earth is the only planet which has developed complicated life structure. If Earth is part of the same source from which other planets have originated there should have been life on other planets too which unfortunately is not there. Why is it so? Why only earth was selected for the complicated evolution of life?
  Some of my friends suggested me that Earth's uniqueness and especially its complex life and atmosphere comes from its location in the solar system which is neither too hot (as in Venus) or too cold (as in Mars and beyond). Again I will say if life would have been there on Mars or Venus they would have adapted accordingly to the earlier atmosphere on these planets as it adapted earlier on the Earth. In our Earth too there are extremes of climates from too hot to cold and the life is surviving here.
  


• The earth and other planets and sun each have a somewhat different density suggesting different time and/or temperatures of origin.
  


• Research comparing silicon samples from Earth, meteorites and planetary materials, published in Nature (28th June 2007), provides new evidence that the Earth`s core formed under very different conditions from those that existed on Mars.
• The giant planets Jupiter and Saturn, essentially of solar composition, are the gasiest. Their satellites and the comets are the iciest.
• How it happens that some planets and satellites have retrograde rotations ( rotate clockwise instead of counterclockwise like the others).
  
  It seems that either Earth originated elsewhere and later became the part of the Solar System. If it has been originated from the same source it must be either younger or older to the other planets. If it is younger then we will have to believe the mythical or religious concept on the origin of the earth. The first recorded biblically estimate of the age of the earth (and universe) was made by Saint Augustine in the fourth century A.D. He counted about 6,000 years from biblical genealogies. Johannes Kepler, then professor of mathematics at Graz, calculated the date of creation to have been 3877 B.C., Sunday, 27 April, at 11 A.M. local time.
  
  All the other planets are devoid of any types of life. Can it be possible that earlier life was there in some of these planets like Mars or Venus and due to effect of climate changes or some other factors life ended on these planets and our planet which I assume is younger to them may face the same fate in coming future. If we assume that Earth is older to the other planets then these planets may in future become like earth.
  
  All ideas concerning the origin of the Earth and the solar system have their problems, and new discoveries often add to the demerits to the theories. All the theories regarding origin of Earth and Solar System are belief systems. Neither one can be proven because no one was there to witness the event, and it can not be repeated. Thus, the origin of the solar system continues to be a problem and even the most modern theories contain many points that need verification.