... Many consider him the greatest navigator of Europe's 16th century age of sea going exploration and credit his expedition with the first circumnavigation of planet Earth. ... A Radar Image of Planet Earth . ... A comet nucleus, formed from the primordial stuff of the solar system, resembles a very dirty iceberg. ... After taking its spectacular pictures of the outer solar system planets, Voyager 1 looked back at six planets from the inner solar system. ... Pluto: The Frozen Planet . ...