Subsurface ice refers to ice deposits that are located beneath the surface of a planetary body such as a planet, moon, or asteroid. These ice deposits can vary in size, thickness, and composition, and can be found in a variety of environments including polar regions, permafrost regions, and beneath the surface of glaciers. Studying subsurface ice is important for understanding the past climates and geological history of a planetary body, as well as assessing the potential for water resources and habitability. Researchers use a variety of techniques such as radar imaging, remote sensing, and drilling to study subsurface ice and its characteristics.