Chang'e 4: China's spacecraft reveals Moon's violent history
The landing site is covered by a layer of loose deposits up to 12m thick.
- China's Chang'e 4 mission has found that the far side of the Moon is covered in a deep layer of loose rock and dust.
- The layer was formed by billions of years of meteorite impacts.
- Scientists believe this could reveal the history of the Moon's far side.
A Chinese probe which became the first spacecraft to land on the far side of the Moon has found the previously unexplored lunar surface to be covered in a layer of loose deposits made up of rock and dust.
This layer, known as lunar regolith, was formed over billions of years by constant meteorite impacts on the surface of the Moon. The findings, published in the journal Science Advances, reveal some of these loose deposits to be up to 12m thick.
As most of the knowledge on lunar regolith comes from NASA’s Apollo and the Soviet Union’s Luna missions to the near side of the Moon, scientists were, until now, uncertain whether these observations would hold true elsewhere on the lunar surface.
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- Chang'e 4: how China's lander talks to us from the far side of the Moon
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Dr Elena Pettinelli, a professor in the mathematics and physics department of Roma Tre University in Italy and one of the study authors, told the PA news agency: “These series of ejecta or deposits came from different impact craters that were created during the evolution of the Moon’s surface.
“It is quite interesting because we can see quite clearly the geological sequences of these events 40 metres below the surface.”
The Chang’e 4 (CE-4) spacecraft landed on the Von Kármán crater on 3 January 2019. Its rover, Yutu-2, which can climb 20-degree hills and 20cm tall obstacles, was deployed 12 hours later to explore the landing site.
Previous landings have been on the near side of the Moon, which faces Earth. The far side, which cannot be seen because it faces away from Earth, has been observed many times from lunar orbits but never explored on the surface.
Using data gathered from the first two days of Yutu-2’s exploration, the researchers identified coarse granular materials up to a depth of 24m below the lunar surface.
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They were able to combine the rover’s high-resolution images and ground-penetrating radar scans from 40m below the surface to create a picture of the Moon’s “internal architecture”. Although the radar signal could not be detected below 40m, the researchers speculate that these granular materials might extend deeper.
Dr Petrenelli said the information gathered from the Yutu-2 rover, along with the data from the previous near-side Moon explorations, could help shed light on the geological history of the lunar surface.
She added: “Maybe we can reconstruct historically the sequence of events in different areas on the Moon.”
Reader Q&A: What is tidal locking?Asked by: Dennis Lund, Salisbury
Tidal locking is the phenomenon by which a body has the same rotational period as its orbital period around a partner. So, the Moon is tidally locked to the Earth because it rotates in exactly the same time as it takes to orbit the Earth. That is why we only see one side of the Moon. If both bodies are of comparable size and are close together, both bodies can be tidally locked to each other – this is the case in the Pluto-Charon system.
Tidal locking is a natural consequence of the gravitational distortions induced by a body on another.