Guest: Gus Frederick was our guest for this Space Show program in order to discuss Martian caves and lava tubes with us. You can follow along in the discussion with these two websites and the instructions provided by Gus: 1) The Caves of Mars located at http://www.highmars.org. 2) Caves of Mars Illustrations located at http://www.highmars.org/marscave. Gus provided other URLs during the show and you will want to see the pictures and graphics he discusses.