China will launch an unmanned craft to the moon this week to bring back lunar rocks - the first attempt by any nation to retrieve samples from Earth's natural satellite since the 1970s.
The Chang'e-5 probe, named for the goddess of the moon, will seek to collect material that can help scientists understand more about the moon's origins.
If successful, the mission will make China only the third country to have retrieved samples following the United States and the Soviet Union decades ago.
Since the Soviet Union crash-landed Luna 2 on the moon in 1959, the first human-made object to reach another celestial body, only a handful of countries including Japan and India have launched missions.
In the Apollo program, which first put men on the moon, the United States landed 12 astronauts over six flights from 1969 to 1972, bringing back 382 kilograms of rocks and soil.
The Soviet Union deployed three robotic sample return missions in the 1970s. The last, the Luna 24, retrieved 170.1 grams of samples in 1976 from Mare Crisium, the Sea of Crises.
China's probe, going within days, will try to collect 2kg of samples from an unvisited area in a lava plain known as Oceanus Procellarum, the Ocean of Storms.
The Chang'e-5 mission may help answer questions on how long the moon remained volcanically active in its interior and when its magnetic field - key to protecting life form from the sun's radiation - dissipated.
Once in the moon's orbit, the probe will aim to deploy a pair of vehicles to the surface: a lander will drill into the ground, transfer its samples to a craft that will lift off and dock with an orbiting module, and then transfer the samples to a capsule to carry them to Earth.
China made its first lunar landing in 2013.
In January 2019, the Chang'e-4 probe touched down on the far side of the moon - a first.
It plans to establish within a decade a robotic base station to conduct exploration in the south polar region.
That will be through the Chang'e-7 and 8 missions through the 2020s and expanded in the 2030s ahead of manned landings.
China plans to retrieve samples from Mars by 2030.
In July, it launched an unmanned probe there - its first to another planet.