Context: China’s Chang’e-6 became the first spacecraft to bring back samples from the far side of the Moon to the Earth.
- The Chang’e-6 probe was successfully launched from China on a Long March-5 rocket on May 3, 2024.
- The lander descended on the Moon’s surface on June 1 and spent two days collecting rocks and soil from one of the oldest and largest of lunar craters — the 2,500 km-wide South Pole-Aitken (SPA) basin — using a robotic arm and drill.
- The lander then launched an ascent module that transferred the samples to the Chang’e-6 orbiter that was orbiting the Moon.
- On June 21, the orbiter released a service module that brought back the samples to Earth. The Chang’e-6 probe returned to Earth on June 25, bringing back the first-ever samples from the far side of the moon.
- Aim: The sample return mission aims to collect and return samples from the far side of the Moon to Earth for analysis. The sample can be rocks or soil or even some molecules.
Is this the first time a spacecraft has brought lunar samples to Earth?
- Back in July 1969, the US Apollo 11 mission brought 22 kg of lunar surface material, including 50 rocks, to Earth.
- In September 1970, the Soviet Luna 16 mission — the first robotic sample return mission — too, brought pieces of the Moon to Earth.
- In December 2020, China’s Chang’e-5 brought back 2 kg of lunar soil.
All these samples came from the near side of the Moon.
- Note:
- China is the only country to achieve a soft-landing on the far side of the Moon. In 2019, its Chang’e-4 mission landed on the far side and explored the Moon’s Von Karman crater with the help of a rover.
- Difficult terrain, giant craters, and the difficulty in communicating with ground control made it technically challenging to land a spacecraft on the far side that never faces the Earth.
Facts about the Moon:
- The Moon is tidally locked to Earth, meaning that the same side of the Moon always faces Earth. This side is known as the near side, while the opposite side is called the far side or the “dark” side (although it does receive sunlight).
- The Moon takes roughly the same amount of time to complete one full orbit around the Earth as the Moon takes to complete one full rotation on its axis.
- As a result, one side of the Moon always faces the Earth, while the other side (far side) faces away from Earth. Thus, we can see only one side of the Moon.
Near side and Far side of the Moon have strikingly different appearances:
Near side:
- The near side is characterised by large, dark basaltic plains called maria (dark spots), which are believed to have formed from ancient volcanic eruptions. These maria cover about 31% of the near side and are less common on the far side.
- The near side also has fewer impact craters compared to the far side.
Far side:
- The far side is more heavily cratered and lacks the extensive maria (dark spots) found on the near side.
- The far side has a thicker crust and is more mountainous, with the highest elevations on the Moon. It has a thicker crust by almost 20 km.
- One of the most prominent features on the far side is the South Pole-Aitken basin, which is the largest known impact crater in the Solar System.
Why are sample return missions significant?
Lunar missions are exploring ways to stay for long on the Moon and to use its resources in situ.
- Detailed analysis of samples:
- In situ robotic explorations — in which landers, orbiters, and rovers carry out experiments in space or on heavenly bodies — can carry only miniature instruments that are not very sophisticated or accurate and have limitations. For example, they cannot determine the origin or age of a rock.
- If the samples can be brought to Earth, the scientists can examine them using extremely sensitive laboratory instruments. They can study the chemical, isotopic, mineralogical, structural, and physical properties of extraterrestrial samples from the macroscopic level down to the atomic scale.
- The returned samples can be preserved for decades and can be examined by future generations using ever more advanced technology.
- Insights into Moon:
- Samples collected from the SPA basin can reveal the timeframe for lunar cratering. The collision that created the basin may have excavated enough material from the Moon’s lower crust and upper mantle, which could give insights into the Moon’s history and its origin.
- An examination of the Chang’e-6 samples could throw up some answers on why the lunar far side is geologically different from the near side.
- Lunar Resources:
- Far side might hold resources like water ice trapped in permanently shadowed craters. Ice can be harvested for water, oxygen and hydrogen — and the latter two can be used in a rocket propellant. These resources could be vital for future lunar settlements or exploration efforts.
- The samples can suggest ways to use lunar resources for future lunar and space exploration. For instance, lunar soil could be used to produce bricks to build future lunar research bases through 3D printing.
- Moon can be used in the near future as a launch pad to travel deeper into space and to other extraterrestrial bodies.
Note:
- India’s Chandrayaan-4 mission, which is currently under development by the Indian Space Research Organisation (ISRO), will also be a sample return mission.
- Chandrayaan-3 landed about 600 km from the South Pole of the Moon in August 2023.