Earth isn’t the only world which accommodates water. There are moons in the Solar System half the size of Earth that hold much more of it. These are known as ocean worlds. Astronomers continue to scrutinise these places in great detail, as they have the potential to change how biology is viewed throughout the universe. “An ocean world is any planet, or sometimes moon, that has at least ten times the amount of water that Earth does. For reference, Earth is about 0.1 per cent water, so an ocean world has a water content of one per cent or greater,” explains Dr Lynnae Quick, an ocean worlds planetary scientist at NASA’s Goddard Space Flight Center in Maryland.
Water is a necessity for life as we know it. Every living thing on Earth consumes water to stay hydrated and survive, from the smallest single-celled organisms to giant mammals. Water also provides opportunities for exploration, whether it’s taking to the oceans to discover a new bit of land or diving into the depths below, where many mysteries remain unanswered. Astrobiologists now want to up the ante and explore the oceans of other worlds millions of miles – and possibly even light years – away in order to find signs of alien life.
How water worlds end up having global oceans, either visible on the surface or buried underneath an icy exterior, is a story in itself. Water does not
