On this day in space! Oct. 20, 1970: The Soviet Union launches last-ever Zond moon mission

On Oct.

20, 1970, the Soviet Union launched the Zond 8 spacecraft on a mission to the moon.

This was the last mission in the Zond program.

After the first three Zond missions explored Venus and Mars , the next ones were circumlunar missions that flew around the moon before returning to Earth.

Although there was no crew on board, the Zond spacecraft was designed with cosmonauts in mind.

The Zond missions served as test flights for the Soviet Union's plans to send cosmonauts to the moon.

But those plans for crewed flights never came to fruition.

This was partly because the U.S. had already put astronauts on the moon , but also because the Zond missions had a lot of technical problems.

Zond 8 was considered a success — even though its guidance system malfunctioned on the way back to Earth.

The spacecraft still returned to Earth safely and splashed down in the Indian Ocean one week after it launched.

The Soviet Union's Zond 8 spacecraft, the last in a series of lunar spacecraft, captured this image of Earthrise on Oct.

24, 1970. (Image credit: Moscow State University of Geodesy and Cartography) Why it mattered While the Zond 1 and Zond 2 missions were launched toward Venus and Mars, respectively, the primary target of most Zond missions was the moon.

At the time, the Soviet Union was embroiled in an ongoing space race with the United States to be the first on the moon with a human crew.

By the time Zond 8 launched on Oct.