BEIJING: China’s robotic Chang’e-5 mission that was sent to a site on the lunar nearside called Oceanus Procellarum has brought back a rock that is 2 billion years old.

The rock and soil samples brought by the spacecraft that was sent in December 2020 were reported to be younger than expected, according to the BBC.

Scientists announced in a study in Science magazine that basalt rocks formed by lava flow collected from the Procellarum region on the moon’s Earth-facing surface are 2 billion years old. To explain the late volcanic activity, scientists said there must be something in that part of the moon that provides heat.

“One of the other options we discuss in the paper is maybe the Moon was able to stay active longer because of its orbital interactions with Earth,” said Dr. Katherine Joy, co-author from the University of Manchester.

“Maybe the Moon wobbled back and forth on its orbit, resulting in what we call tidal heating. So, a bit like the Moon generates ocean tides on Earth, maybe the gravitational effect of the Earth could stretch and flex the Moon to generate frictional melting,” she told the BBC.

It was previously reported that rock samples collected by Apollo astronauts are more than 3 billion years old.

Chang’e-5 returned to Earth on Dec. 16, 2020. It was the first spacecraft to return samples from the moon to Earth in more than 40 years since the US’ Apollo missions in the 1970s and the Soviet Union’s Luna missions.

China, which landed its Chang’e-4 robotic vehicle on the dark side of the moon in 2019, was the first country to achieve that feat.