Although the mass of oceans on the Earth is a tiny fraction (0.023 wt%) of the bulk Earth mass, the existence of oceans is sufficient to distinguish the Earth from the other planets in the solar system. Water is essential for the origin and evolution of life, the stability of the surface environment, and the evolution of the planetary interior. At present, we have no definite answers to fundamental questions about the origins of water on the Earth. The process by which water was supplied to the Earth is thought to be closely related to the dynamics of the solar system. Because of several uncertainties about the planet formation process (the position of the snow line in the solar nebula, the lifetime of the nebula gas, the timing of the formation of Jupiter, etc.), the origins of the Earth's oceans are still much in question. In this paper, we describe several possible sources of the Earth's water in the solar system and possible processes by which water was supplied to the Earth. Within the context of the modern theory of planetary formation, we discuss several scenarios for the origins of the Earth's oceans.
