China’s Chang’e 6 probe returned to Earth on Tuesday with rock and soil samples from the little-explored far side of the Moon in a historic first.

The probe landed in northern China in the Inner Mongolian region.

Chinese scientists anticipate that the returned samples will include 2.5-million-year-old volcanic rock and other material it is hoped will answer questions about geographic differences on the Moon’s two sides.

While past United States and Soviet missions have collected samples from the Moon’s near side, the Chinese mission was the first that has collected samples from the far side.

The far side is also known to have mountains and impact craters, contrasting with the relatively flat expanses visible on the near side.

The probe left Earth on May 3 and its journey lasted 53 days, during which it drilled into the Moon’s core and scooped rocks from the surface.

The samples “are expected to answer one of the most fundamental scientific questions in lunar science research: what geologic activity is responsible for the differences between the two sides?” said Zongyu Yue, a geologist at the Chinese Academy of Sciences.

The statement was issued in Innovation Monday, a journal published in partnership with the Chinese Academy of Sciences.

In recent years, China has launched multiple successful missions to the Moon, previously collecting samples from its near side with the Chang’e 5 probe.

They are also hoping that the probe will return with material that shows traces of meteorite strikes from the Moon’s past.