Our ocean covers 72% (and rising) of this small planet and is home to most of the globe's biomass, or living matter, and biodiversity. We know that from bacteria to plankton to the blue whale, life in the ocean greatly affects life on land, yet we know very little about the ocean. At least 80% is yet to be explored. Conceptual computer artwork of the total volume of water on Earth (left) and of air in the Earth's atmosphere (right) shown as spheres (blue and pink). The spheres show how finite water and air supplies are. The water sphere measures 1,390 kilometres across and has a volume of 1.4 billion cubic kilometres. This includes all the water in the oceans, seas, ice caps, lakes and rivers as well as ground water, and that in the atmosphere. The air sphere measures 1,999 kilometres across and weighs 5,140 trillion tonnes. As the atmosphere extends from Earth it becomes less dense. Half of the air lies within the first 5 kilometres of the atmosphere.