http://www.helium.com/knowledge/208533-57-alien-species-are-we-alone-in-the-universe.xml Helium.com > Astronomy > 57 alien species: Are we alone in the universe? en-us Copyright Helium.com Tue, 20 Jan 2009 20:32:22 GMT Tue, 20 Jan 2009 20:32:22 GMT