The Origin of Water on Earth

the role of water in the life of the earth

Water is a vital element that is the key to life on earth. Without water, there would be no sea, rain, plants, or even humans. However, the big question that has long made scientists curious is: where does the water on our planet come from? Given that the earth was formed about 4.5 billion years ago in very hot conditions, the existence of large amounts of water as it is now becomes an interesting mystery to reveal.

Currently, about 71% of the earth’s surface is covered in water. Scientists believe that water does not come from only one source, but the result of a combination of various processes—both from within the Earth itself and from outer space—which occurred during the early days of the formation of the planet. Let’s completely forget about the origin of the existence of water on earth!

Challenges in the Early Solar System

At the beginning of the formation of the solar system, the temperature in the area near the sun, including where the earth was formed, was very high. Under such conditions, the ice could not survive. If there is water vapor, it will most likely evaporate and release into space. Earth-forming materials, called planetesimals, are formed in relatively dry environments. However, the analysis of the isotope of hydrogen in modern seawater shows that the water-forming elements may have existed since the early stages of planet formation, although in limited quantities.

Internal source: water from within the earth

It is possible that some of the water on Earth comes from within the planet itself. In the early days, the earth had a magma ocean with a temperature of more than 4,000 Kelvin. Under high pressure conditions, hydrogen can dissolve in magma. This hydrogen then reacts with oxygen in the minerals to form water. The enstatite chondrite meteorite—which is similar in composition to the Earth’s mantle—contains enough hydrogen to produce water up to three times the current volume of the ocean if it is released.

In addition, the minerals in the mantle, such as ringwoodite and wadsleyite are capable of storing hydrogen and oxygen. Through geological activities such as convection and volcanic eruptions, water from within the earth is slowly released into the surface in a process called Outgassing.

Asteroid Rain: Introduction to Water from Space

Apart from the inside, water is also thought to come from outer space, especially through asteroid collisions. About 4 billion years ago, there was a period known as the Late Heavy Bombardment, where many asteroids hit Earth. Carbon-rich asteroids from the outer asteroid belt contain large amounts of water ice. Interestingly, the composition of the isotope of hydrogen (the ratio of deuterium to hydrogen) of these asteroids is very similar to the water on Earth, thus reinforcing the theory that they are one of the main sources of water on our planet.

Giant Collision and the Beginning of the Ocean

Another theory that is no less interesting is the big collision between the young earth and the Martian-sized object called Theia. This event is believed to form the moon. The collision may also bring water-rich material from the outside of the solar system to Earth. Although some of the water evaporates due to extreme heat, over time the earth cools, the water vapor condenses into rain and begins to form the first ocean. Evidence of the presence of liquid water is even found in ancient zircon crystals which indicate that water has existed about 100 million years after the sun was formed.

Comet role: not as big as expected

In the past, comets were considered the main source of water because of their abundant ice content. However, over time it is known that the isotope ratio in comet water is different from water on Earth. This has led scientists to conclude that comets account for only a fraction of water, not the main source.

So, the origin of water on Earth is the result of a long process involving cosmic forces and complex chemical reactions. From the depths of the mantle to the impact of asteroids from outer space, all play a role in forming the ocean which is now the source of life. Understanding the origin of water is not only a matter of the past, but also helps us understand how other planets might keep life in the future.