This video describes the creation of water in the solar system. It goes onto explain the three theories as to how the Earth’s water was obtained. Following that, it addresses the presence of water in the solar systems and discusses how prevalent it is in different forms.

Why Watch This Video?

  1. Have you ever wondered how the Earth got water?
  2. Would you like to know how the first water molecules in the solar system were created?
  3. Have you ever been confused about the commonality of water in the solar system?

Key Terms

Carbonaceous chondrite– asteroids that contain water molecules along with their raw elements of oxygen and hydrogen. Thought to have brought a good percentage of Earth’s surface water.

Primordial H2O– ancient water molecules

Condensation nuclei– Tiny particles of dust that act as vessels to carry condensed water vapour molecules

Loose Ends

How does water get released from within the Earth?

Water vapour is the most abundant volcanic gas, which suggests the vast majority of the water was actually released from within the Earth by volcanic activity. Volcanic activity is created because of plate tectonics.

If there is so much water around the solar system, why hasn’t there been life discovered elsewhere?

Because of Earth’s position in the solar system, life is able to thrive. The location allows for the perfect temperature where water remains in its liquid state. The size of the Earth is also a factor because any larger and the gravity would be too dense to admit sunlight, any smaller would lack gravity enough to retain an atmosphere.

Why is so little of Earth’s water freshwater? Why is the sea salty?

The rain that fell on early Earth would have contained almost no salts because it was derived from water vapour. Some salts were brought to early seawater by rivers that carried the products of weathering on land. At the same time, the seawater that seeped into mid-ocean ridges and returned to the ocean carried with it ions of elements such as calcium and potassium that were liberated in the chemical alteration of newly formed oceanic crust. Calculations show that seawater should have become approximately as saline early in Archean time as it is now. Seawater’s total salinity has varied only modestly, even though the relative proportions of dissolved ions have varied significantly. At the same time, the global water cycle has moved water, but not salts, from the oceans to the atmosphere and back again

Self-Test Questions

Scroll down for the answers.

1. What contributes the least amount of water to Earth’s total water presence?

  1. Oceans
  2. Biological
  3. Ice/Snow
  4. Vapor
  5. b & d

2. What aspect is thought to have contributed the most amount of water to Earth?

  1. Water built into the planet during its creation
  2. Earth created water as it cooled
  3. Space rocks brought water
  4. They all contributed equal amounts

3. What evidence led to the conclusion that water was brought by asteroids rather than comets?

  1. The ratios of heavy hydrogen
  2. The colour of the water
  3. The time of origin
  4. The debris remaining on Earth

4. When was the earliest water in the solar system formed?

  1. 4.9 billion years ago
  2. 7.2 billion years ago
  3. 12.7 billion years ago
  4. 38.1 billion years ago

5. In which layer of the Earth was water separated into “Hs” and “OHs”?

  1. Crust
  2. Mantle
  3. Outer core
  4. Inner core


1. E: Biological and Vapor both contribute 0.001% of Earth’s total water. Oceans consist of the most, which is 96.54% of the Earth’s water and ice/snow consists of 1.74%.

2. C: Space rocks were thought to have brought most of Earth’s water, but the amount of water that was built into Earth during creation is still not exact and there may be oceans worth of water deep within the Earth.

3. A: The ratios of heavy hydrogen. The atomic fingerprint of water we find on Earth (1.56 × 10-4) does not quite match what we see in comets (2 × 10-4 to 5.3 × 10-4) and matches closer to what we see in asteroids (0.1 × 10-4 to 2 × 10-4).

4. C: Hydrogen would have been created when the Big Bang happened, so oxygen would have been the element needed to create water. Oxygen is stored inside stars, so the earliest water would have been able to form when the very first stars in the universe ignited, which was around 12.7 billion years ago at the earliest.

5. B: Water existed separated into Hs and OHs in the rock of the mantle and we are unsure how much water is still locked inside of the Earth today. The water found on the crust is most often H2O molecules rather than separated.

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Item Credit: It's Okay to Be Smart, PBS Digital Studios

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