... One of the most unusual galaxies known, Centaurus A, is pictured above. Cen A is marked by dramatic dust lanes that run across the galaxy's center. ... Two Tails of Comet West . ... 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. ...