China’s rock samples from the far side of the Moon have returned to Earth

The first-ever samples from the far side of the Moon have touched down on Earth. China’s Chang’e 6 capsule landed on Tuesday in Inner Mongolia, carrying rocks that could confirm or debunk scientists’ current theories about the Moon’s origin.

The samples could help scientists confirm the current hypothesis about the Moon’s origin: that molten Earth collided with a body around the size of Mars, ripping off material that took orbit next to us and created the Moon.

“Think about the geology of the Earth: If you only landed in North America, you’d be missing a big part of the story, right?” Richard Carlson, director emeritus of the Earth and Planets Laboratory at Carnegie Science, told NPR.

Researchers believe that if China’s rock samples show the same age as what NASA’s Apollo program brought home last century, it would confirm the hypothesis. If it doesn’t, it would throw a wrench into the works, forcing us to revise our understanding of the Moon’s birth.

“It’s pretty clear that the far side and the near side have many, many differences,” Jim Head, a planetary scientist at Brown University, said to NPR. “It’s a really critical issue. You can’t understand the origin of a planet with one hemisphere.”

Chang’e 6 landed on the Moon’s far side early this month, only the second successful mission to the end of Earth’s neighbor that always faces away from it. The pair rotates synchronously, keeping one side perpetually hidden from our view. This makes landings difficult because Earth has no direct line of communication with the far side, forcing China’s space program to rely on a satellite relay instead.

China has offered to share some of the samples with American scientists in a sign of cooperation during otherwise tense times between the two nations. NASA has given the green light for US researchers to submit proposals to study the historical samples.