The Source Of WATER

So guys, today I am back with my  second blog. Today I will try to explain and investigate the potential source of water on our sweet planet Earth. But before I start, I would like to inform you that I may not be writing for a few upcoming weeks due to some personal reasons. So let's get started......

Water... H2O... which is alternatively known as Life. Water is one of the most essential building blocks and sustaining element of life. Without water, life couldn't have been formed. We know that first living organisms, and cellular evolution took place in water. So we all know and even feel today, that WATER is exclusively a valuable gift. But how on earth water came? The question though sounds an easy one, but the answer to it is still ambiguous and unclear!

Timeline of Earth (Source: Wikipedia)

The Earth was formed nearly about 4.54 billion years ago. But the formation of water on earth was not that straight forward. We all were taught in our elementary sciences that water on earth was formed due to the condensation of vaporized H2O due to gradual cooling down of our planet. But this could not have supplied us so much of water that has kept 71% of the crust covered. So this hypothesis primarily faces two significant challenges:

Primitive Earth

1.  The water we had was already there in those proto-planetary  objects those formed our planet. But this assumption cannot be appropriate as Earth is a rocky planet, and since rocky planets are formed from rocky pieces, they must not have water with them. Even if you assume such anomaly, then still those watery rocks which may have formed our earth, they could not contain water because the position was too close to our highly radio active baby Sun, which used to go under Rapid Coronal Mass Ejections (the large flares emitted from Suns's surface), so water would have gone away easily.
2. The earth while being formed, had lesser gravity (due to lesser mass), and tremendous heat, so easily many gases escaped from earth, and water vapor being lighter would have done so. At that time atmosphere was not there to entrap those vapor. So water might not be on earth, or might be in lesser amount than today. That is why Hydrogen and helium are present in lesser quantity.

So facing above challenges, scientists were sure that the water we are using today (and that too had been even used by dinosaurs) must have come from other sources too. The first doubt was The Comets & Asteroids from Asteroid Belt. The main driving force for such thought was the presence of huge water reservoirs in those extraterrestrial objects & during that primitive ages, thousands of asteroids and comets hit earth, so water might have come from them. So, scientists compared the Deuterium (A heavier radioactive isotope of Hydrogen) to Hydrogen ratio of terrestrial water to that of those astronomical entities (by spectroscopical methods and other asteroid and cometary missions viz. Rosetta mission, Dawn mission etc.). The ratio resulted to be lower for terrestrial water when compared Comets, but matched with that of asteroids. 

Now the water present in asteroids are really insufficient in amount to fill the oceans of earth. So, it's evident that asteroids could not have done this alone. Also the rocks brought from Moon during Apollo 13 and Apollo 17 missions, resulted in observations that those rocks have the same Deuterium (D) to Hydrogen (H) ratio as that in Earth, which hinted to same source of watery material. And the D/H ratio of comets were done under the standard observations made from  Halley's Comet, Hyakutake, Hale–Bopp, and 67P/Churyumov–Gerasimenko. But though these are believed to be Kuiper Belt objects, but reality of them are doubtful. 

Interestingly, amount of water those cold Kuiper Belt objects hold, can fill all Earth's oceans for more than 20000 times! And if in reality, Halley and other comets appear to be non Kuiper belt objects, then there is a high probability that most of terrestrial water has come from Kuiper Belt. But how? Those are far away and hardly such objects enter into inner solar system, so how they helped to fill our oceans?

In the answer, Jupiter and other gas giants play a huge role. The orbital positions of Jupiter & Co. (comically writing such name to indicate all gas giants) are weird. They should not be where they are present today, not even with so much mass, cause no such gas-giants are allowed to form at such distance to its host star due to lack of formation elements (the details on this I will discuss in future blogs). So it is believed to be formed at the outer side of the then solar system. But when they grew much bigger to shift the Barycenter (the equilibrium center of gravity, defined for objects in a stellar system) of Solar System, that imbalance led to shift their orbit to where they are now. But their sudden shifting produced a Gravitational turbulence at outer solar system. As a result, thousands of Outer Solar Icy Kuiper Belt objects were plunged into inner solar system. And thus those intruding objects, while hitting Earth, contributed in the formation of oceans on Earth. 

The theory is well fitted with present conditions and observations. And the reality has higher probability to match with it due to facts related to Gas giants involved here are not assumptions rather true. But this also indicates, that other planets, like Venus and Mars and Mercury might have received such water too, but how they lost that, will be discussed in future contents.

So stay tuned, and comment your opinions, you may also write to me to suggest me Topics to write on, mail me at kuntalzatchhindi@gmail.com.

Our Blue Planet