At 02:10am on 8 May, China's Chang’e 6 spacecraft entered orbit around the Moon, ahead of its attemped landing on the lunar far side.
Chang’e 6 launched on 3 May from the Wenchang Space Launch Centre on China’s current most powerful rocket, the Long March 5, and is bound for the far side of the Moon, where it will collect a sample of lunar material and return it to Earth for study.
If all goes to plan, it will be humanity’s first sample from the region, representing an important symbolic, scientific and possibly strategic win for the rising space power.
Although this is not even China's first sample-return mission to the Moon.
On 16 December 2020, the return capsule of the Chang’e 5 mission landed in China’s Inner Mongolia Autonomous Region.
It had travelled hundreds of thousands of miles from the Moon, carrying 1,731g (61 oz) of precious lunar dust.
Remarkably, this represented the first lunar sample return mission since the USSR’s Luna 24 brought back 170g (6 oz) in August 1976.
There's no 44-year wait this time though, as China's next lunar sample-return is already underway.
Chang'e 6 mission key facts
Chang'e 6 is composed of four independent modules: the lander, the ascender, the orbiter and the return vehicle, with an estimated total mass of 8,200kg (18,077lb).
After entering lunar orbit, the lander will separate from the orbiter vehicle and descend to the lunar surface.
It will perform a fully autonomous soft landing in the South Pole–Aitken Basin, a 2,500km-diameter (1,550 mile) impact crater on the far side of the Moon.
The South Pole–Aitken (SPA) Basin is understood to be the largest, deepest and oldest crater on the Moon (4.2–4.3 billion years), with an unusual geochemical composition that is different from the rest of the lunar surface.
Collecting the lunar sample
To date, China’s Chang’e 4 lander and rover are the only spacecraft to have touched down on the lunar far side.
It’s been surveyed by several lunar orbiter missions, but as the Soviet and US missions of the ’60s and ’70s remained on the near side, no samples have ever been retrieved from the region.
The samples Chang’e 6 collects will enable further study of the region’s composition, giving scientists a much better understanding of the formation of the Moon.
The impact that created the South Pole–Aitken Basin is believed to have excavated deep into the lunar crust.
This could potentially provide insights into the geological composition of the lunar interior.
Once on the surface, the Chang’e 6 lander has a drilling capacity of up to 2m.
The lander is expected to scoop up around 2kg (4.4lb) of material (about the same as the previous mission) which it will transfer to the sample-return container using a robotic arm.
This will then be stored in the ascender, which will launch from the top of the lander and rendezvous with the orbiter.
The samples will then transfer to the return vehicle to head back to Earth.
When they are 5,000km (3,100 miles) from Earth, the return vehicle will separate from the orbiter ready for atmospheric re-entry.
Parachutes will carry the capsule through its final stages to land in Siziwang Banner, Inner Mongolia.
Chang'e 6 mission duration
While the Chang’e 5 mission lasted 22 days, Chang’e 6’s duration is expected to be 53 days, largely due to the added complexity of landing on the far side of the Moon.
As the far side never faces Earth, due to a phenomenon known as tidal locking, the lander will communicate with the Chinese teams on the ground using the Queqiao-2 relay satellite.
The nascent lunar Queqiao satellite constellation is a key part of China’s long-term lunar plans.
It will support the upcoming Chang’e 7 and 8 missions as well as Chang’e 6, and helps pave the way for the upcoming International Lunar Research Station (ILRS), a joint Chinese–Russian megaproject planned for the 2030s, which will aim to establish a long-term presence on the lunar surface.
This makes Chang’e 6 an important part of China’s long-term space programme.
The bigger picture
China’s lunar exploration efforts are managed by the China Lunar Exploration Program (CLEP), a sub-unit of the China National Space Administration (CNSA).
The programme consists of four phases:
Phase 1
Chang’e 1 and 2, which reached lunar orbit in 2007 and 2010, undertaking mapping and remote sensing missions.
Phase 2
Chang’e 3 and 4 (plus Queqiao-1), which placed a lunar lander and rover on the Moon’s surface in 2013 and 2018.
Phase 3
Chang’e 5, which collected lunar samples in the Moon’s Mons Rümker area in 2020 and returned them to Earth.
Phase 4
Chang’e 6, 7 and 8, which will aim to develop technologies for long-term exploration of the Moon, and prepare for China’s future lunar station, the ILRS.
The last two missions are expected to fly in 2026 and 2028 respectively.
China's missions to the Moon
Despite not formally starting until 2004 – more than 30 years after the US’s first Apollo missions – China’s lunar exploration interests date to the early 1990s, when proposals were considered under a national high-tech development plan known as Program 863.
But lunar plans only formally began after China orbited their first astronaut, Yang Liwei, in 2003.
Since then, the country has seen five consecutive successful missions, each helping to “cross the river by feeling the stones” – a Chinese phrase for navigating a complex situation by small, measured steps.
With ever more ambitious and higher-profile missions, China has built up a world-class space infrastructure, becoming a highly regarded potential partner for space programmes across the world.
But any country with a substantial lunar programme needs good reasons for embarking on such a programme.
Lunar missions cost billions of dollars, present a significant risk and occupy many of a country’s brightest technical minds.
China’s reasons are sometimes opaque but seemingly manifold, including scientific progress, resource utilisation, international diplomacy and soft power.
Why the Moon ?
Scientific advancements form a pivotal aspect, with a focus on advancing the understanding of lunar geology, geochemistry and topography.
These in turn can provide valuable information on the early history of the Solar System and Earth.
The Moon’s proximity to Earth is also a key enabler for China to develop space-based technologies in areas such as biology, medicine and astronomy.
Resource exploration is another key driver of China’s lunar endeavours.
China is very interested in the potential presence of ice in the permanently shaded regions at the Moon’s poles – an interest shared by other major space powers.
This common interest is reflected in recent and upcoming missions from the US, China, India and others targeting the lunar south pole.
Notably, ice can be harvested for water, oxygen and hydrogen, the latter two serving as a rocket propellant combo.
The Moon is also known to have noteworthy concentrations of helium-3, a rare resource crucial for nuclear fusion.
Additionally, China envisions the Moon as a potential source for substantial economic development.
While obviously to be taken with a grain of salt, in late 2019, prominent Chinese space industry figure Bao Weimin proposed the creation of a new space economy he dubbed “the Earth–Moon Economic Zone”, projecting an economic output of up to $10 trillion by 2050.
As for diplomacy and soft power, several previous Chang’e missions have featured instruments from international partners, and Chang’e 6 will have four scientific instruments on board from France, Italy, Sweden and Pakistan, adding a diplomatic dimension to the missions.
Longer term, the joint Chinese–Russian lunar station, the ILRS, is being touted as an alternative to the US-led Artemis programme.
As of March 2024, six countries in addition to China and Russia had signed up, namely South Africa, Pakistan, Egypt, Belarus, Venezuela and Azerbaijan.
The samples
The lunar samples Chang'e 6 brings back will also provide opportunities for international collaboration.
When Chang’e 5’s samples were returned to Earth, the Chinese gave domestic institutions initial priority access to them before granting access to international partners 2.5 years later.
It’s expected the Chang’e 6 samples will be treated the same way.
The Chang’e 5 and 6 samples give China an important bargaining chip in international space diplomacy, with NASA having applied to receive Chang’e 5 samples in late 2023 after receiving permission from the US government to do so.
No doubt they and other institutions will be even more eager to get their hands on the lunar rocks Chang’e 6 brings back from the lunar far side, so they can take the first-ever look at this mysterious world that is usually hidden from our view.
Chang'e 6 instruments
In April 2018, the China National Space Administration put out a call for international partners to submit proposals for experiments Chang’e 6 could carry to the Moon.
A total of 10kg (22lb) of payload mass was available and the following four were selected.
DORN (Detection of Outgassing Radon)
An alpha spectrometer that will study the transportation dynamics of radon and other elements between the lunar soil, known as regolith, and the exosphere, the Moon’s extremely thin atmosphere. The instrument is being provided by the French Research Institute of Astrophysics and Planetology (IRAP).
INRRI (INstrument for landing – Roving laser Retroreflector Investigations)
INRRI is a passive laser retro-reflector that will be available for future lunar missions to use for optical range-finding. It is being built at the SCF Lab in Rome, Italy.
NILS (Negative Ions on Lunar Surface)
A mass spectrometer to measure the negative ions that are emitted from the lunar surface due to its interaction with the solar wind. The NILS instrument is the brainchild of the Swedish Institute for Space Physics.
ICUBE-Q
A cubesat that aims to detect traces of ice on the lunar surface. It is being constructed by the Islamabad Institute of Science and Technology in Pakistan, with co-operation from Shanghai Jiao Tong University.
This article appeared in the May 2024 issue of BBC Sky at Night Magazine
