As India marks the first anniversary of the successful landing of its unmanned spacecraft on the moon, Indian scientists have confirmed, after studying the lunar soil recovered by one of the instruments on the Chandrayaan-3 mission, the most widely held hypothesis on the early evolutionary history of the moon that the lunar surface was covered with an ocean of molten material (magma) in its early periods.

The moon was entirely an ocean of magma when it formed. As the magma cooled, heavier minerals such as olivine and pyroxene sank and formed the inner layers of the moon while the lighter mineral plagioclase floated and formed the outer crust of the moon, according to parts of the studies shared by the Indian Space Research Organisation.  

The Alpha Particle X-ray Spectrometer (APXS), one of the two instruments on the rover of Chandrayaan-3, has provided the first information on the top soil composition in the southern latitudes of the moon.

From the APXS-measured composition, the scientists of the Ahmedabad-based Physical Research Laboratory inferred that the lunar soil is a mixture of two types of rocks named Ferroan Anorthosite (FAN), rich in plagioclase mineral, and Magnesian Suite (Mg-suite).

While the dominant mineral present is plagioclase, as expected in lunar highland terrain, other minerals, olivine and pyroxene, are higher than typically expected in the outer crust of the moon.

The south pole basin on the moon, the largest known impact basin in the solar system, is believed to have been formed about 4.2–4.3 billion years ago due to an asteroid’s impact which resulted in the excavation of Mg-rich material from deeper layers of the moon and brought to the surrounding areas, including the Chandrayaan-3 landing site, which is about 350km away from the rim of the south pole region of the moon.  

Subsequent cratering caused the mixing of the surface material with the material from deeper layers to form the soil with the composition seen by the APXS.

The Vikram Lander of India’s Chandrayaan-3 mission made the historic moon landing on 23 August 2023. The Pragyan rover deployed on the lunar surface explored the nearby area by traversing about 103 metres over the next ten days.