Changes

#[[Titan]], a moon of [[Saturn]], has approximately the same percentage of [[nitrogen]] in its atmosphere as in Earth's. Titan also has [[ocean]]s and thick clouds. Scientists have determined that the oceans are liquid [[methane]], not water, and that the low temperatures of -178° Celsius make life, at least as we know it, highly improbable.

#[[Titan]], a moon of [[Saturn]], has approximately the same percentage of [[nitrogen]] in its atmosphere as in Earth's. Titan also has [[ocean]]s and thick clouds. Scientists have determined that the oceans are liquid [[methane]], not water, and that the low temperatures of -178° Celsius make life, at least as we know it, highly improbable.

=== Extraterrestrial Civilizations ===

== Extraterrestrial Civilizations ==

Do one or more extraterrestrial civilizations exist? Until recently, speculation about extraterrestrial races was confined either to [[science fiction]] or to innumerable anecdotal reports of "[[UFO|unidentified flying objects]]." These latter reports were once the subject of an investigation, known as Project Blue Book, by the [[United States Air Force]].<ref>Anonymous, "[http://www.ufoevidence.org/topics/ProjectBlueBook.htm Project Blue Book]", ''[http://www.ufoevidence.org/ UFO Evidence.org]'', retrieved April 16, 2007</ref><ref>Anonymous, ''[http://www.bluebookarchive.org/ The Project Blue Book Archive]'', retrieved April 16, 2007</ref><ref>Fund for Unidentified Flying Object Research (FUFOR), ''[http://www.nicap.org/index.htm Official Site of the National Investigative Committee for Aerial Phenomena]'', Francis L. Ridge, editor and Webmaster, December 15, 1997 to present. Retrieved April 16, 2007.</ref><ref>Presumably the [[Union of Soviet Socialist Republics|Soviet]] Army Air Forces had their own version of Blue Book as well.</ref> But years after Blue Book wound down, a large cadre of scientists began to entertain seriously the notion that extraterrestrial civilizations might exist.

Do one or more extraterrestrial civilizations exist? Until recently, speculation about extraterrestrial races was confined either to [[science fiction]] or to innumerable anecdotal reports of "[[UFO|unidentified flying objects]]." These latter reports were once the subject of an investigation, known as Project Blue Book, by the [[United States Air Force]].<ref>Anonymous, "[http://www.ufoevidence.org/topics/ProjectBlueBook.htm Project Blue Book]", ''[http://www.ufoevidence.org/ UFO Evidence.org]'', retrieved April 16, 2007</ref><ref>Anonymous, ''[http://www.bluebookarchive.org/ The Project Blue Book Archive]'', retrieved April 16, 2007</ref><ref>Fund for Unidentified Flying Object Research (FUFOR), ''[http://www.nicap.org/index.htm Official Site of the National Investigative Committee for Aerial Phenomena]'', Francis L. Ridge, editor and Webmaster, December 15, 1997 to present. Retrieved April 16, 2007.</ref><ref>Presumably the [[Union of Soviet Socialist Republics|Soviet]] Army Air Forces had their own version of Blue Book as well.</ref> But years after Blue Book wound down, a large cadre of scientists began to entertain seriously the notion that extraterrestrial civilizations might exist.