Fifty years ago this month, the Soviet Union scored a coup in the space race with a probe called Luna 2. The spacecraft, which resembled a squat, souped-up version of its cousin Sputnik, was launched on September 12, 1959, and two days later reached the lunar surface. By impacting the moon, Luna 2 became the first man-made object to land on a celestial body other than Earth.

Just under 10 years later, of course, humans would follow Luna 2 to the surface of the moon. But nowadays, as in 1959, the most distant journeys are carried out by unmanned probes.

Here is a look at five robotic space missions that could extend our understanding of the solar system in the coming years.