In other interplanetary explorations without astronauts, Mariner 10 spacecraft three times passed by Mercury, the planet closest to the sun, revealing its similarity to both the earth and the moon.

• 其它无人驾驶的星际探险，主要有水手号太空船三次经过最靠近太阳的行星水星，揭示出水星与月球，地球的相同点。