Chandrayaan-2 radar data reveals strong evidence of subsurface ice in lunar south pole craters
Bengaluru, June 11. Scientists from the Physical Research Laboratory (PRL), Ahmedabad, have identified strong indications of subsurface water ice beneath several permanently shadowed craters near the Moon’s south pole using data collected by the Chandrayaan-2 orbiter, the Indian Space Research Organisation (ISRO) announced.
The findings are based on observations from the Dual Frequency Synthetic Aperture Radar (DFSAR), a microwave imaging instrument operating in L- and S-band frequencies aboard Chandrayaan-2. The payload is the first fully polarimetric synthetic aperture radar deployed to study the Moon.
The study focused on so-called “doubly shadowed craters” located within permanently shadowed regions (PSRs) of the lunar south pole. These areas remain in perpetual darkness and are shielded from both direct sunlight and thermal radiation, maintaining extremely low temperatures of around 25 Kelvin. Such conditions are considered ideal for preserving water ice over billions of years.
Through advanced radar polarimetric analysis, researchers detected signatures consistent with the possible presence of subsurface ice beneath the floors of four doubly shadowed craters. The team developed a refined radar-based criterion to distinguish genuine ice deposits from signals caused by rough, rocky terrain.
According to the study, Circular Polarisation Ratio (CPR) values greater than one, combined with Degree of Polarization (DOP) values below 0.13, indicate volumetric scattering that could be associated with buried ice. DOP is a radar parameter that measures how much of the reflected signal retains its original polarisation after interacting with surface or subsurface materials.
Among the craters examined, a 1.1-km-wide crater located within the larger Faustini crater exhibited particularly compelling evidence of subsurface ice. Scientists said the feature not only displayed radar characteristics indicative of ice but also possessed distinctive lobate-rim morphology, a flow-like structure that may have formed when an impact penetrated an ice-rich subsurface layer.
The findings add to growing evidence that the Moon’s south polar region contains significant reserves of water ice, a resource regarded as crucial for future long-duration lunar exploration and the establishment of sustained human presence on the Moon.
The study further highlights the scientific capabilities of Chandrayaan-2 and the important role of radar observations in understanding the composition and evolution of the lunar surface.
