美宇航局:土星卫星有可能取代地球

　　Scientists from NASA have found evidence of life on Saturn's biggest moon, Titan。

　　Data from NASA's Cassini probe analyzed the complex chemistry on the surface of Titan - the only moon known to have a dense atmosphere. Its surface is covered with mountains, lakes and rivers which has led astronomers to call it 'the most Earth-like world in the solar system'。

　　Liquid on Titan is not water but methane, which leads scientists on a guess that life on the moon could be methane-based. The hydrogen gas flowing down through Titan's atmosphere disappears in the surface, suggesting it could be being breathed by alien bugs。

　　NASA astrobiologist Chris McKay said: 'If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water.'

　　Scientists believe that when the Sun swells up in four billion years, swallowing the Earth, conditions could be ideal on a warmer Titan。

　　Professor John Zarnecki, of the Open University, said: 'We believe the chemistry is there for life to form. It just needs heat and warmth to kick-start the process. In four billion years' time, when the Sun swells into a red giant, Titan could become a paradise.'