Subsurface ice in doubly shadowed craters as revealed by Chandrayaan-2 dual frequency synthetic aperture radar

Doubly shadowed craters at the lunar poles provide ideal environments for preserving subsurface ice. Located within permanently shadowed regions, their raised rims additionally block scattered light and thermal emission from nearby illuminated surfaces, allowing crater interior temperatures to reach around 25 K. Using full-polarimetric L- and S-band observations from Chandrayaan-2’s Dual Frequency Synthetic Aperture Radar, we investigate the presence of subsurface ice in nine doubly shadowed craters located within Faustini, Haworth, and Shoemaker craters. Four craters exhibit circular polarization ratio values greater than 1 together with low degrees of polarization (<0.13), allowing us to establish a refined diagnostic criterion for identifying subsurface ice through volumetric scattering. A ~ 1.1 km wide crater within Faustini shows enhanced radar polarization and a prominent lobate-rim morphology, indicating potential excavation into subsurface ice. These observations provide strong evidence for subsurface ice in doubly shadowed craters and support long-term volatile retention processes at the lunar poles.