Part of the Moon fell to Earth: How Chandrayaan-3 solved ancient lunar mystery

A PRL study has linked Chandrayaan-3's Shiv Shakti soil readings with the lunar meteorite ALHA 81005. The match offers fresh evidence on the Moon's crust and how lunar material reached Earth.

In Short

• Pragyan examined lunar soil chemistry at Shiv Shakti Station after landing
• Researchers compared the readings with 66 lunar meteorites found on Earth
• ALHA 81005 from Antarctica showed the closest geochemical match to samples

Nearly two years after Chandrayaan-3's historic landing near the Moon's South Pole, scientists have uncovered a remarkable link between the lunar surface and a meteorite discovered on Earth more than four decades ago.

A new study by researchers at the Physical Research Laboratory (PRL), Ahmedabad, has revealed that the chemical composition of soil analysed by the Pragyan rover at Shiv Shakti Statio closely matches ALHA 81005, the first meteorite ever confirmed to have originated from the Moon.

The findings provide one of the strongest pieces of evidence yet connecting Chandrayaan-3's in-situ measurements with lunar rocks that were blasted off the Moon and eventually landed on Earth.

After Chandrayaan-3's successful landing on August 23, 2023, Pragyan's Alpha Particle X-ray Spectrometer (APXS) examined the elemental composition of lunar soil at the Shiv Shakti Statio, located at 69.37° South, 32.32° East in the Moon's southern highlands.

Scientists compared these measurements with the compositions of 66 known lunar meteorites recovered from different parts of Earth. Among them, ALHA 81005, discovered in Antarctica's Allan Hills during the 1981-82 Antarctic expedition, emerged as the closest geochemical match.

The discovery does not mean the meteorite originated from the exact Chandrayaan-3 landing site. Instead, researchers say both the meteorite and the landing region represent the same rare type of magnesium-rich lunar crust.

The APXS measurements showed the Shiv Shakti Station contains lower aluminium but higher iron and magnesium than typical lunar highland regions. Scientists also found elevated levels of olivine relative to pyroxene, another characteristic shared with ALHA 81005.

"This is one of the first studies to directly connect Chandrayaan-3's in-situ measurements with lunar meteorite records," the researchers said.

The findings also offer new insights into the Moon's violent geological past.

Researchers believe the soil at the Chandrayaan-3 landing site is not derived solely from the Moon's upper crust. Instead, it appears to contain fragments of magnesium-rich rocks excavated from deeper layers during the formation of the gigantic South Pole-Aitken Basin, one of the largest and oldest impact craters in the Solar System located roughly 350 kilometres from the landing site.

This supports the long-standing Lunar Magma Ocean hypothesis, which suggests the early Moon was once covered by a global ocean of molten rock.

As this magma ocean cooled, different minerals crystallised at different depths, creating the layered lunar crust seen today.

The study It also demonstrates how Chandrayaan-3 is helping scientists reconstruct the evolution of the Moon's ancient crust and better understand how lunar material has travelled across space to eventually reach Earth.

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