Water is composed of two atoms: hydrogen and oxygen. Hydrogen atoms were formed during the creation of the universe and are the oldest element in the universe. Oxygen is formed during the burning of carbon inside intermediate-mass stars. Hydrogen and oxygen combine to form water. Water is the source of all known life. The earth was first formed as a hot fireball. About 200 million years after its formation, the earliest oceans were formed, but they were difficult to persist due to frequent meteor impacts. About 400 million years later (about 4 billion years ago), the primitive ocean finally formed and has changed to this day.
In the solar system, ice-covered planets and moons are common, but only the stable presence of liquid water-oceans-can breed life. So, where is liquid water stored in the universe? Are there any oceans beyond the earth? Not long ago, scientists had always believed that the Earth was the only planet in the solar system with a liquid water ocean, and therefore believed that an environment capable of maintaining a liquid water ocean was extremely rare. In fact, the existence of water is quite common in the solar system, and there are also larger oceans outside the earth than on earth. Now that humans have detected a planet with oceans outside the solar system, we may know whether there will be life there in the near future.