Lunar Subsurface Ice Detection with Cosmic Rays

Evidence of water ice deposits in the Permanently Shadowed Regions (PSRs) on Mercury have engendered investigations for ice in the Moon’s PSRs. However, continued radar investigations into the Moon’s polar regions lack conclusive evidence for ice in radar backscattering data due to volume scattering and surface roughness. These previous radar experiments have ruled out shallow regions for ice deposits, but not at depths > 5 m. The radio signature produced in ultrahigh energy (UHE) particle showers, known as the Askaryan signal, offers a novel approach to probe deeper than previously achievable in search for buried ice deposits. Due to the linear polarization of the Askaryan signal, the dielectric properties of an ice layer would manifest as a polarity flip relative to direct measurement. The Cosmic Ray Lunar Sounder (CoRaLS) is a proposed lunar orbiter mission that will leverage the polarity flip in the Askaryan pulse upon reflection to determine the existence, location, and ice purity of these deep subsurface ice deposits.