A contextual map of the Chandrayaan-3 landing site (yellow circle) with data from LRO WAC showing nearby craters. Scale bar, 50 km. Credit: Nature 2024
India's Chandrayaan-3 mission has uncovered evidence of a former magma ocean near the Moon's South Pole, a region previously unexplored in such detail1.
This discovery was made by the Pragyan rover deployed by the Vikram lander in August 2023.
During its nine-day mission, Pragyan traversed 103 meters, stopping at 23 locations. Using an alpha particle X-ray spectrometer, the rover analyzed the Moon’s regolith — the outermost layer of lunar soil. The findings, analyzed by Santosh Vadawale and his team at the Physical Research Laboratory in Ahmedabad, revealed that the regolith around the landing site had a uniform elemental composition, primarily composed of ferroan anorthosite rock.
Vadawale says these results bolster the lunar magma ocean hypothesis, which posits that the Moon’s mantle formed as heavier materials sank inward while lighter rocks floated to the surface, creating the outer crust. Interestingly, the chemical makeup of the regolith near the South Pole closely matches that of soil samples from equatorial and mid-latitude regions, further supporting this theory.
Pragyan also provided new insights into the geology of the area. Up to 50 meters around the landing site, the terrain is relatively smooth, with no visible craters or boulders. Beyond this zone, the rover encountered boulders likely ejected from nearby craters and observed formations near the rims of small craters.
Understanding the elemental composition of the lunar surface at this site offers a crucial "ground truth" that can inform future remote-sensing missions and the planning of subsequent lunar landings, Vadawale says.
