发现外星生命

 When and where do you think we will find extraterrestrial life？ 你以为咱们会在何时何地发现外星生命？
　　“If there is abundant microbial life on Mars， I suspect that we will find it within 20 years—if it is enough like our form of life. If an alien life-form differs much from what we have here on Earth， it is going to be difficult to detect. It’s also possible that any surviving Martian microbes are rare and located in places that are difficult for a robotic lander to reach. Jupiter’s moon Europa and Saturn’s moon Titan5） are more compelling places. Europa is a water world where more complex forms of life may have evolved. And Titan is probably the most interesting place in the solar system to look for life. It is rich in organic molecules but very cold and has no liquid water； if life exists on Titan， it will be very different from life on Earth.”
　　—Carol E. Cleland， philosophy professor at the University of Colorado Boulder

　假如火星上存在很多的微生物，我猜想20年内咱们就能发现外星生命——假如这些生命与咱们的生命方式满足类似。假如外星的生命方式与咱们地球上的生命方式相差太大，那将难以发现。也有或许火星上存活的微生物太稀疏，且都生存在登陆机器人难以触及的当地。木卫二和土卫六是更具吸引力的星球。木卫二上有很多的水，在那里更高档的生命方式或许现已进化。要想寻觅生命，土卫六也许是太阳系中最风趣的当地。那里有很多的有机分子，但十分冰冷，而且没有液态水。假如土卫六上存在生命，必定与地球上的生命方式截然不同。”
　　——科罗拉多大学博尔德分校哲学教授卡罗尔·E·克莱兰德