The ISS can perform experiments in weightlessness that cannot be performed on Earth. The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology, and other fields. The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars.
Astronauts perform many tasks as they orbit Earth. The space station is designed to be a permanent orbiting research facility. Its major purpose is to perform world-class science and research that only a microgravity environment can provide. The station crew spends their day working on science experiments that require their input, as well as monitoring those that are controlled from the ground. They also take part in medical experiments to determine how well their bodies are adjusting to living in microgravity for long periods of time.