Moon’s Ancient Magma Ocean: Chandrayaan-3’s Latest Discovery

Just ahead of National Space Day, commemorating the first anniversary of India’s Chandrayaan-3 mission’s successful landing on the Moon’s south pole—a significant discovery has emerged from data transmitted by the Pragyan rover. Indian scientists, led by Santosh Vadawale from the Ahmedabad-based Physical Research Laboratory (PRL) under the Department of Space, have uncovered new insights into the Moon’s geological history.

Uniform Lunar Soil Composition Unveiled

The research team revealed that the lunar regolith (the outermost layer of soil) surrounding the Chandrayaan-3 landing site has a uniform elemental composition, primarily consisting of ferroan anorthosite rock. This discovery was made using the Alpha Particular X-Ray Spectrometer (APXS), one of the key instruments on the Pragyan rover. The findings, published in the journal Nature on August 21, highlight the significance of this region, which had previously remained unexplored by humans.

Supporting the Lunar Magma Ocean Hypothesis

The PRL team’s analysis also supports the lunar magma ocean hypothesis, a widely-accepted theory that suggests the Moon was once entirely an ocean of magma. According to this theory, as the magma cooled, heavier minerals sank to form the Moon’s inner layers, while lighter minerals like plagioclase floated to the surface, forming the outer crust. The dominant presence of ferroan anorthosite in the soil near the landing site further confirms this hypothesis. Additionally, the presence of Mg-rich materials indicates that the outer crustal material has mixed with deeper layers of the Moon, providing a more complex picture of the Moon’s geological evolution.

Insights into Lunar Geology

Pragyan’s data also shed light on the geology of the area around the landing site. The terrain within a 50-meter radius is relatively smooth, with no visible craters or boulders. However, beyond this zone, the rover encountered boulders likely ejected from nearby craters and observed formations near the rims of small craters. These findings suggest that the lunar soil in this region is a mixture of materials from different depths, offering direct insight into the Moon’s evolutionary history.

Ground Truth for Future Missions

The analysis, based on 23 measurements taken at different locations within 50 meters of the landing site, showed that the lunar regolith’s uniform elemental composition makes it an excellent “ground truth” for future remote sensing missions. APXS used techniques such as X-ray Fluorescence Spectroscopy and Particle Induced X-ray Emission to detect and quantify various elements in the lunar soil. Over the mission period of 10 days, the instrument carried out two dozen scientific observations along the rover’s path, providing invaluable data on the Moon’s surface composition.

Revealing the Moon’s Evolutionary History

The new measurements by APXS in this previously unexplored region of the Moon indicate that the lunar soil is a mixture of different rock types, with some material excavated from deeper layers of the Moon. This discovery offers direct insight into the Moon’s evolutionary history, further enhancing our understanding of Earth’s only natural satellite.