From Lake Vostok to Europa: Tractors and satellites -- Water below the central part of the ice sheet -- Does subglacial water exist? -- Discovery of subglacial lakes by radio-echo sounding -- The need for reinterpretation of seismic data -- A thick water layer exists under Vostok Station! -- Deep drilling at Vostok Station -- Vostok Station and the ice shelf -- New data on Lake Vostok -- Plan for the international study of Lake Vostok -- Penetration of Lake Vostok. The first book on the subject, this monograph examines the phenomenon of a huge sealed, freshwater lake, isolated from the rest of the world by kilometers' thick ice. The existence of melting ice at the bottom of the huge Vostok Lake has served as a model and inspired the team planning the Galileo space craft to gather data on the ice sheet of the Jupiterian moon Europa. The book provides interpretation of, and calculations for, stimulating factors for possible melting and a huge lake's existence at the bottom of the Martian ice sheets.