Answer the following question given this paragraph: 

Humans have walked on only two planetary bodies: Earth and the Moon. The footprints the men left behind are the first signs of life ever on the Moon. Scientists learned a great deal about the Moon from the Apollo missions. The samples that were brought back have been studied in laboratories. We know an incredible amount about the Moon because of these samples. Having these rocks radically changed our thinking about the Moon.


Q: Which two planetary bodies have humans walked on?


A:
earth and the moon