Complex sentence: Luna 16 was the first robotic probe to land on the Moon and return a sample to Earth and represented the first lunar sample return mission by the Soviet Union and the third overall, following the Apollo 11 and Apollo 12 missions.
Split into simpler sentences: Luna 16 was the first robotic probe to land on the Moon and return a sample to Earth. It represented the first lunar sample return mission by the Soviet Union, and was the third lunar sample return mission overall, following the Apollo 11 and Apollo 12 missions.