Water is essential for life as we know it. It is present throughout the Solar System, and was part of the Earth from its formation. The source of the water was the same as the source of the Earth's rock : the cloud of particles which condensed in the origin of the solar system.
- The cycle starts when water on the surface of the Earth evaporates. Evaporation means the sun heats the water which turns into gas.
- Then, water collects as water vapor in the sky. This makes clouds.
- Next, the water in the clouds gets cold. This makes it become liquid again. This process is called condensation.
- Then, the water falls from the sky as rain, snow, sleet or hail. This is called precipitation.
- The water sinks under the surface and also collects into lakes, oceans, or aquifers. It evaporates again and continues the cycle.