It was a triumph of international collaboration - a laboratory for hundreds of astronauts - but was the 120 billion dollar investment worth it? Considered as one of humanity’s greatest achievements, it was built by the USA, Russia, Canada, Europe and Japan. Since it launched into space in 1998, over 270 astronauts from around the world have conducted research in the orbiting laboratory, but it is due to be retired in 2030. So how significant has it been and what will replace it? Host Claire Graham talks to the BBC’s Science Correspondent Pallab Ghosh. We also examine the economic opportunities offered by the moon and ask if China is the emerging space power.