A human lunar return study is when scientists study what happens to people when they go to the moon! Scientists have been studying what happens to people when they go to the moon for a very long time. They collect data on how their bodies, minds, and other aspects of their lives change. They are studying things like how their muscle strength, bones, vision and balance are affected by the change in gravity and environment. They are also looking at how different tasks or activities affect them and how the effects of space travel can be managed for future missions. By studying people who have gone to the moon and come back to Earth, scientists are hoping to learn more about the effects of space travel and how space explorers can be kept safe on long-term missions.