China launches Chang'e 6 sample-return mission to moon's far side

China is headed back to the moon's mysterious far side — and this time, the nation will bring back some souvenirs.

The robotic Chang'e 6 mission launched Friday (May 3) at 5:27 a.m. EDT (0927 GMT; 5:27 p.m. Beijing time), riding a Long March 5 rocket off a pad at the Wenchang Space Launch Site, in southern China's Hainan province.

If all goes according to plan, Chang'e 6 will touch down on the moon's far side, scoop up some samples and rocket them back to Earth — something that's never been done before. Indeed, just one mission has ever soft-landed on the lunar far side: Chang'e 4, which put a lander-rover duo down in January 2019.

The moon's hidden face

The moon is tidally locked to Earth, completing one rotation in the same amount of time it takes to orbit our planet. This means that observers on Earth only ever see one face of the moon — what we call the near side.

In addition to being more familiar than the far side, the near side is easier for us to explore, which explains why every surface mission prior to Chang'e 4 — including NASA's crewed Apollo efforts in the late 1960s and early 1970s — had targeted that face. 

A rover or lander mission to the far side faces communications challenges, requiring a lunar orbiter to relay messages to and from mission control here on Earth. China launched just such a relay satellite, called Queqiao, ahead of Chang'e 4 and sent another one, Queqiao 2, toward lunar orbit this past March to prepare for Chang'e 6 and subsequent surface missions.

There are compelling reasons, beyond the spirit of curiosity and exploration, to study the far side up close, scientists stress. It's very different from the near side; for example, while large plains of basalt known as maria cover about one-third of the moon's familiar face, these dark "seas" of volcanic rock comprise just 1% of the far side's surface.