Chandrayaan-3 Landing Site May Hold Moon’s Ancient Deep Rock: PRL Study

The reference is to rock from deep inside the Moon that has remained largely unchanged since its formation over 4 billion years ago.

The Chandrayaan-3 landing site is seen to be a promising place for future missions to collect samples, particularly to study the early evolution of the Moon.

Scientists at the lab have analysed the concentrations of volatile elements measured at Shiv Shakti station near the South Polar Region, using the Alpha Particle X-ray Spectrometer (APXS) onboard the Pragyan rover of the Chandrayaan-3 mission.

A comparison of the APXS measured abundances with the other available data revealed anomalous depletion in sodium and potassium, but enrichment in sulfur in the soils at the highland landing site.

This study published in the journal Nature Communications Earth and Environment has revealed potential presence of primitive lunar mantle materials at the landing site, which was excavated during formation of the South Pole-Aitken (SPA) basin 4 billion years ago and redistributed by subsequent impacts on the SPA basin ejecta.

The primitive mantle contributed the excess sulfur, which got mixed up with the materials at the landing site.

The low levels of sodium and potassium at the landing site suggests that the KREEP (potassium, rare earth elements, and phosphorus) might not have existed at the place and time of SPA basin formation.

This new finding makes the Chandrayaan-3 landing site a promising site to access primitive mantle samples, which is otherwise lacking in the existing lunar collections.

On 23 August 2023, the Chandrayaan-3 mission marked the first successful landing in the South Polar Region of the Moon.

The Alpha Particle X-ray Spectrometer (APXS) aboard Pragyan rover directly measured the elemental composition of the Moon’s surface at unexplored location --ie, the Shiv Shakti station located at 69.37° S, 32.32° E in the southern high-latitude highlands of the nearside of the Moon.

The APXS measurement of major elements supported the lunar magma ocean (LMO) hypothesis. It also provided clues for the presence of lower crust and/or upper mantle materials at the landing site.

APXS also measured abundances of volatile elements, including sodium, potassium and sulfur in the highland soils and reported varied concentrations ranging from 700-2800ppm, 300-400ppm and 900-1400ppm respectively.

The scientists in Ahmedabad have made a detailed analysis of the abundances of these volatile elements.

They reported that the concentration of sodium and potassium at the Chandrayaan-3 landing site was found to be much lower compared to what was found in the soil samples from lunar highlands in earlier missions (Apollo 16 and Luna 20). The concentration of sulfur was found to be 300-500 ppm higher than in soils from Apollo 16 and Luna 20 missions.

The anomalous differences in the concentration of these volatile elements make it important to investigate the probable source that led to their enrichment or depletion at the Chandrayaan-3 landing site.

To summarize, a comparison of volatile elemental abundance data from Chandrayaan-3 soil relative to previous missions suggests much lower amounts of sodium and potassium, but higher levels of sulfur.

Such a pattern indicates that the soil at the landing site includes primitive mantle material excavated by the SPA basin impact, billions of years ago.

That makes the Chandrayaan-3 landing site a promising place for future missions to collect samples for studies about the evolution of the Moon, scientists said.