Moon’s Hidden Reservoirs: Chandrayaan‑2 Radar Lifts The Lid On Buried Ice

Chandrayaan‑2 was placed in lunar orbit with a microwave imaging instrument called Dual Frequency Synthetic Aperture Radar (DFSAR) which can explore a few metres beneath the lunar surface. The radar sent waves toward the permanently shadowed craters near the south pole, and then measured the echoes. The scientists at ISRO and Physical Research Laboratory were able to detect patterns that matched the underground ice and not bare rock or dry dust.  

The scientists examined nine “doubly shadowed” craters, and identified four that had radar signatures that were very consistent with the presence of water-ice in the subsurface. They used two parameters: Circular Polarization Ratio (CPR) and Degree of Polarization (DOP). Regions showing CPR values greater than one and DOP below about 0.13 pointed to “volumetric scattering”, a tell‑tale sign that radar waves were interacting with icy material mixed within the regolith instead of just rough terrain. One 1.1 km wide crater within the larger Faustini basin was particularly striking, and was found to have a distinct lobate rim shape that indicates an impact may have penetrated an ice-rich layer. The results make the south pole of the Moon an ideal location for future ISRO and international missions looking at in situ resource utilisation.