21.   Vast amounts of liquid water on early Mars not only raises hopes that life evolved there, but also that it could still survive today.

22.   Pitre proposed an amendment removing all references to Darwin, who developed the theory that all life evolved from simple forms through a process of natural selection.

23.   In this solar system alone, there are at least four places besides Earth where life could have evolved.

24.   Some have a lifetime too short to allow life to evolve.