What are the ways water got or formed on Earth?

Scientists have been thinking about this question for a while but still do not know the answer. I am researching this topic because it is fascinating and cool to research. I will also learn a lot. It is also important to research because then people will know how water got on exoplanets. I want to see how some planets have water. I also have some experience on this topic because I know why water is important for life.

I will research using different reliable websites and books. My parents and teachers will also help me and give me tips.

How I classify what a reliable website is: The first thing I do is make sure that I do not use Wikipedia for my research. This is because people can edit and put whatever they want on the website. The second thing I check if a reliable website is reliable is the layout of the website. If it is messy and includes too many ads, I will not use the website in my research. I will also check the About Us. Then, if they meet all the criteria I will use the website.

Research:

 

What is water:

Water is a molecule composed of hydrogen and oxygen. Water is chemically called H2O. This means there are two hydrogen molecules (H2) and one oxygen molecule (O). Water is an extraordinary molecule because all life needs it. However, where did water come from? There are a few theories on how water got on Earth.

A water molecule.

 

 

Why does life need water:

Life needs water because water helps dissolve important nutrients and move them to your cells. It can dissolve more compounds than any other liquid. This means it is a universal solvent. It is like this because the hydrogen side of water is a positive electrical charge and the oxygen side is a negative charge. This means that positive or negative atoms can still be attracted atoms with a charge (some atoms called neutral atoms don’t have charges). It also helps remove toxins from your body.
 

 

 

Spectroscopy:

Scientists know how water is on other planets by using a technique called spectroscopy. Spectroscopy works by seeing what wavelengths molecules absorb. A wavelength is the distance between a crest and the next nearest one. The next step in spectroscopy is to see if there is a strong absorption of that specific wavelength.E.g.: To see if water is on an exoplanet, we check if there is a strong absorption of infrared wavelengths; which water absorbs.

A wave.

 

On a light scale; water absorbs microwave well.

 

 

Habitable Zone:
Another reason why we have water on Earth is because we are in the habitable zone. If we were in the back of the solar system and watery asteroids crashed into the planet, the water would just freeze and would be useless. If the watery asteroids crashed into Mercury, it would melt and not help life. We are in a special spot in the solar system where water is a liquid, which is useful for life. We also are in a special type of habitable zone. The CHZ is a continuously habitable zone. It is a place where water can exist for long periods.

A diagram of a habitable zone.

 

Theia:
Theia was the planetoid that crashed into the Earth to form the moon. The pieces that got off the planetoid formed the moon. When it crashed, it could have given the Earth some of its water if it had some. There is another piece of evidence too. The composition of the mantle and the crust come from the outer solar system. People know this because they check it with where the element molybdenum came from.

The molybdenum from the mantle came from the collision with Theia. The results also showed that the elements came from the outer solar system. This means Theia came from there. Everything that comes from the Kuiper belt has ice on it. When Theia crashed into the Earth, the ice could have melted and given Earth water.

An artist's impression of Theia.

 

Planetesimals:
Another way water could have gotten on Earth is from planetesimals. Planetesimals are water-rich objects. These objects could have been asteroids or comets. They could have been made in the outer solar nebula of the early solar system where there was a lot of water ice. Then they could have crashed into the Earth. The heat of the crash would have melted the ice resulting in water.

 

 

Comets:
The possibility of comets bringing water to us was later ruled out because they had a different amount of deuterium than the oceans. Scientists now say that comets did not bring water to the Earth because of this. There is a small exception though. Water from certain types of comets DO have the same amount of deuterium as the Earth’s ocean. These comets would have to travel very far to get to Earth. Even if they could get here, simulations show that these comets would only have made up 6% of Earth’s water.

 

A comet (Comet Hale-Bopp)
 

 

Asteroids:
There have been at least 190 asteroid/comet impacts that have hit the Earth. The scientists found this number by scanning all the craters in the world. There is very likely to be more because the Earth’s surface is changing all the time and the craters would have disappeared. All or most of them could have carried water to the Earth. There also could have been smaller asteroids that could have given water to the Earth.
The evidence for the asteroid theory is that the amount of deuterium in our water is the same as the asteroids.

A carbonaceous chondrite meteorite.

 

Stars:
A way water could have been made is from stars. Inside stars, a reaction called nucleosynthesis of nuclear fusion happens. This means making heavier elements from lighter ones. The two elements needed for water, hydrogen and oxygen are made in nucleosynthesis. When the stars explode, they release all the elements. When the oxygen and hydrogen react, they can become water or hydrogen peroxide. Hydrogen peroxide is the thing you have in your first aid kit to disinfect wounds. It can become oxygen and water if it is heated because it is very unstable.

Nucleosynthesis.

 

A hydrogen peroxide molecule. It is made of hydrogen & oxygen. The H2O could have broken off and left the oxygen, the two most important elements needed for life.

 

How water from stars gets to the Earth:
The water that came from the star would get to Earth through asteroids. The water could have gone to the asteroid and taken a ride on it. Another way water molecules could have gotten to the Earth is by floating through space. The molecules could have bombarded the Earth and given it water. This is different from asteroids and comets because they also deliver water much more slowly. The water molecules would have to do this for billions of years to get some water. This is comets because comets are balls of snow.

 

Volcanic Outgassing:
One way water could have gotten out of the Earth is that the rocks that made up the Earth might have had water in them. The water might have gone up by volcanoes along with the magma. The water vapor could have gone into the atmosphere condensing then raining down as rain.
 

The 4 main theories of how water got on Earth:

1. The first way is that the planetoid Theia which crashed into the Earth and made the moon had water on it. When it crashed into the Earth, it gave some or most of its water to the Earth.

2. The second way water could have gotten on Earth is that water rich objects, planetesimals, crashed into the Earth in its early history and gave it water. The comets or asteroids had ice on them. When they crashed into the Earth, it melted all the ice and it became water.

3. The third way water could have gotten on Earth is that the rocks that made up the Earth had water on them. Volcanoes took that water out from the ground and they outgassed any of it as water vapor. It then went into the air and rained dow as liquid water.

4. A theory that I found was that when stars exploded, they gave away new elements to the universe. One of them was oxygen. The oxygen could have combined with hydrogen, one of the most abundant elements in the universe, to make H₂O, and water. These elements were present in the solar cloud where the solar system was formed.  The water could have gone on asteroids and the asteroids collided with the Earth or the water molecules could have crashed into the Earth by themself, giving the Earth some water.

In conclusion, stars, volcanic outgassing, planetesimals, and Theia might have given us water, or any combination of them might have given the Earth water. My hypothesis was included in the results and I still think that it is the most likely way water could have gotten on the Earth because there were many asteroid bombardments in Earth’s history. I also think this is the theory because we know a lot about it and a lot of the evidence is pointing toward this theory.

 

This topic was very fun to research. I learned many new things doing this.

Books & websites

 

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I would like to thank Aayan Abdullah for helping me format the slides, Mr.Z for giving me tips, Khoa Nguyen (My father) for teaching me APA citations and checking my work for grammar mistakes, Van Nguyen (My mother) for making sure I had enough information, and Neal Bhuller for support