Subsurface oceans refer to bodies of water that exist beneath the surface of a planetary body, such as a moon or planet. These oceans are typically located beneath a thick layer of ice or rock, and may be kept in a liquid state due to heat generated by the planetary body's core or tidal forces from nearby astronomical bodies. Research in subsurface oceans focuses on understanding the geology, chemistry, and potential habitability of these hidden water bodies. Scientists study the composition of the water and the surrounding rock, as well as any signs of potential life forms that may exist in these extreme environments. Subsurface oceans are of particular interest for astrobiologists, who believe that these environments may harbor microbial life and provide valuable insights into the potential for life beyond Earth.