On June 4, a spacecraft from the Chang’e 6 lunar lander flew away, carrying valuable soil and rock samples from the far side of the moon.
This handout photo, taken on June 3 and released by the CNSA on June 4, shows the ascender and lander taken by the Chang’e 6 lunar probe after it landed on the moon. | Photo credit: Handout/AFP
the story So Far: Early in the morning on June 4 (IST), a small spacecraft carrying lunar samples flew past the far side of the moon and reached an orbit that would bring it into contact with an orbiter waiting for it. There, Chang’e 6 the spacecraft will ‘hand over’ the samples to a capsule on the returner, which will eventually bring the samples back to Earth in a two-week journey. Thus, scientists will finally get access to the first pieces of lunar soil and rocks. All the spacecraft in this mission are part of China’s ambitious and ongoing Chang’e 6 mission.
What are Chang’e missions?
China’s moon missions are called Chang’e, named after the moon goddess in Chinese mythology.
The China National Space Administration (CNSA) launched the Chinese Lunar Exploration Program (CLEP) in 2003, and the first Chang’e mission launched in 2007. Chang’e 1 mapped the moon’s surface.
With Chang’e 2, CLEP launched Phase I of its lunar mission, and equipped the orbiter with an improved camera. The pictures taken by this camera were used to prepare the lander and rover of the Chang’e 3 mission for landing on the Moon, which they successfully achieved on December 14, 2013, and began CLEP’s Phase II mission.
Chang’e 4 was the precursor to Chang’e 6: in 2019, it carried the first lander and rover to land on the far side of the Moon and explore this relatively more mysterious region. To achieve this, another spacecraft was first needed around the Moon to ‘communicate’ between Earth and ground stations on the far side of the Moon. That same year, CLEP said China would land an astronaut on the Moon within a decade.
Phase III began with the Chang’e 5 mission. In late 2020, it deployed a lander on the near side of the Moon. This included a mission component called the Ascender, which, after collecting and storing soil samples (specifically, the youngest volcanic lunar soil samples ever found), launched itself into orbit. There, an orbiter collected the samples, transferred them to a returner, and the returner brought them to Earth.
As CLEP’s second Phase III mission, Chang’e 6 is attempting to repeat the feat of its predecessor — except for the far side of the moon. This time, the scientific goal is to understand why the far side is so different from the near side.
What is the far side?
The Moon is tidally locked to Earth: the lunar hemisphere facing toward Earth will always remain facing toward Earth, and the hemisphere facing away will always remain facing away. The terrain on the far side is rockier and has less smooth plains than the near side. Scientists believe this is due to the heat released by Earth when the Moon was formed and the thermochemical characteristics of the Moon’s near side.
In fact, it’s difficult to land a spacecraft on the far side – all the more so because it’s impossible to communicate directly with the spacecraft from Earth: there’s no line of sight. A common solution is to have a second spacecraft in space that relays signals between ground stations on Earth and the surface spacecraft, making the mission more complicated.
The Earth shields the far side of the Moon from the solar wind, which is expected to help the far side retain more helium-3. There has been a lot of excitement in the past about using this isotope in advanced fusion reactors – especially after former Indian Space Research Organisation (ISRO) chairman K. Sivan said so in a statement in 2018. But the technology for this fusion does not exist yet.
The far side is also expected to be a good place to install large telescopes, allowing a view of the universe without the obstruction of the Earth. Scientists from ISRO and Raman Research Institute, Bengaluru are currently working on such a telescope, called PRATUSH.
What is the status of Chang’e 6?
The CNSA launched the 8.3-ton Chang’e 6 orbiter-lander combination on May 3, and it entered lunar orbit on May 8. The lander complex separated from the orbiter on May 30 and landed on June 1 over a large crater called the Apollo Basin. Apollo itself is located within the much larger South Pole-Aitken Basin.
CLEP scientists coordinated this part of the mission with the help of the Queqiao 2 relay satellite, which the CNSA launched into an elliptical orbit around the Moon in February this year. Its second relay satellite, Queqiao 1, is in a halo orbit around the second Earth-Moon Lagrange point. (Note: Aditya-L1 is in a halo orbit around the second Earth-Moon Lagrange point.Sun Lagrange point.)
After landing in the Apollo Basin and turning on, a drill penetrated the soil, and with the help of a scoop, extracted about 2 kilograms of far-side material, and transferred it to the ascender. On June 4, the ascender flew to lunar orbit, where it is expected to rendezvous with the orbiter, transfer the samples to a capsule in the returner, which is expected to eventually return to Earth, crashing somewhere in Inner Mongolia on June 25.
What can the samples reveal?
Since Chang’e 6 is a Chinese mission, the ‘what’ depends as much on the samples as ‘by whom’ and ‘when.’ The CNSA is not sharing timely and detailed updates, as is expected from other space programs.
Once the CNSA retrieves the sample-bearing capsule, Chinese scientists will have the chance to work on it first, after which they will share access with foreign research groups based on their proposals. It is unknown whether any Indian research groups have applied for access.
Scientifically, remote samples are expected to provide insight into why the Moon is the way it is and how the planets formed.
When China completed the Chang’e 5 mission, it became the first country to successfully carry out a robotic lunar sample return mission since the Soviet Union’s lunar sample return mission in 1976. China was also the first country to execute an autonomous soft-landing on the far side of the Moon with its Chang’e 4 mission and – if the returner brings the samples safely back to Earth – will become the first and only country to do so from the far side of the Moon.
The CNSA is expected to launch asteroid and Mars sample-return missions in 2025 and 2030, respectively.
India currently has no plans to explore the far side of the Moon. ISRO’s Chandrayaan programme is expected to launch a lunar sample-return mission in 2028, but this is likely to be delayed. India is a signatory to the US-led Artemis Accords, an arrangement under which India and other accord members will share information to pursue more collaborative exploration of the Moon over the next decade.
China is not a part of this agreement.
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