When earth is seen from outer space,it looks mainly blue. This is because most of the earth is covered with.

Water

water. The reason why Earth appears mainly blue when seen from outer space is because around 71% of the planet's surface is covered by water. This includes the vast oceans, seas, lakes, and rivers. When sunlight strikes the Earth's surface, it interacts with the water molecules, causing them to absorb and scatter light in a specific way. This scattering process predominantly reflects the blue wavelengths of sunlight, giving the oceans their distinct blue color. Hence, when viewed from space, the abundance of water on Earth gives it a predominantly blue appearance.