China's lunar spacecraft started its journey back to earth after collecting samples from the far side of the moon, the country's space agency said on Tuesday. 

The China National Space Administration (CNSA) said the ascender module of the Chang'e-6 probe unfurled the Chinese flag before lifting off. 

The craft was the first to ever successfully take off from the moon's far side. 

The mission comes as China advances its space program, aiming to put a person on the moon before the end of this decade. 

Why is the mission important?

The so-called dark side of the moon, which is invisible from Earth, is believed to have great potential for research as its craters are less covered by ancient lava flows than the near side.

Scientists say material collected from the far side of the moon may help in studying how it was formed. 

The mission was widely hailed in China, with Chinese state news agency Xinhua describing it as "an unprecedented feat in human lunar exploration history."

Ge Ping, the mission's spokesperson, said analyzing the collected samples would allow scientists "to deepen research on the formation and evolutionary history of the moon."

It can also offer insights into "the origin of the solar system ... laying an improved foundation for later exploration missions," he added.

What is China's Chang'e-6 probe?

The probe's 53-day mission began on May 3. On Sunday, it touched down in the moon's immense South Pole-Aitken Basin, which the CNSA says is one of the largest known impact craters in the solar system. 

According to the Chinese agency, Chang'e-6 faced a challenge of high temperature, as well as lack of direct communications with ground stations on Earth. 

The probe relied instead on relay satellite Queqiao-2, which was put into orbit in April for communications.

To collect samples, the probe used a drill to gather material under the surface and a robotic arm to grab specimens above the surface, according to Xinhua.

The probe's predecessor, Chang'e-5, retrieved samples from the near side of the moon. 

fb/nm (AFP, AP, Reuters)