Scientists who studied images from the mission and satellites believe Chandrayaan-3, India's lunar mission, landed in one of the Moon's oldest craters.
According to a team of researchers from the Physical Research Laboratory and Indian Space Research Organisation (ISRO) in Ahmedabad, the crater was created during the Nectarian period, which dates back 3.85 billion years and represents one of the Moon's earliest historical periods.
S Vijayan, an associate professor in the Planetary Sciences Division at the Physical Research Laboratory, stated to PTI, "Chandrayaan-3's landing site is a distinctive geological environment that no other missions have visited. The images from the mission's Pragyan rover provide the first on-site views of the Moon at this latitude, revealing the Moon's evolutionary history."
A crater forms when an asteroid collides with the surface of a larger celestial body like a planet or a moon, and the displaced material is referred to as 'ejecta'.
The images demonstrate how one half of the crater was covered by material ejected from the South Pole-Aitken basin, the Moon's largest and most well-known impact basin, providing insight into the Moon's historical evolution.
An impact basin is a large, intricate crater with a diameter exceeding 300 km, while a crater is defined as having a diameter of less than 300 km.
Forming of ejecta is "similar to when you throw a ball on sand and some of it gets displaced or thrown outwards into a small pile," explained Vijayan, who is the corresponding author on the study that appeared in the journal Icarus.
"When an impact basin is forming, surface material will be thrown out. If the diameter of the impact basin is larger, sub-surface materials from greater depths will be excavated," Vijayan said.
In this case, Chandrayaan-3 was found to have landed within a crater -- about 160 km in diameter -- and detected in the images as a nearly semi-circular structure.
The researchers said this likely indicated one half of the crater, the other half of which was 'degraded' by getting buried under ejecta from the South Pole-Aitken basin.
"Further, near the landing site, ejecta or material 'thrown out' from another impact crater further away was observed -- images captured by the Pragyan rover revealed that material of the same nature was present at the landing site," Vijayan said.
The Pragyan rover was deployed on the lunar surface by the Vikram lander, on-board the Chandrayaan-3.
"Together, the images from the mission and satellites showed that the Chandrayaan-3 landing site consists of material deposited from different regions of the Moon," he said.
The mission, launched by ISRO, Bengaluru, made a soft landing near the Moon's south pole on August 23, 2023. The landing site was christened the Shiv Shakti Point on August 26, 2023.
For validating their results, the researchers also observed other craters formed during the Nectarian period and found that most of them were severely degraded and modified -- a finding that "substantiates our discovery of a buried crater." The finding is also an indication of the weathering effects due to exposure to space, or 'space weathering,' they said.
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