We might not be here without the Moon
See astronomer Neil F. Comins' book What if the Moon Didn't Exist?, which
began as a series of astronomy magazine articles.
http://www.astrosociety.org/education/publications/tnl/33/33.html
http://home.att.net/~storytellers/nomoon.html
In addition to all that the Moon's presence has done to help keep Earth
stable enough to produce life, as a place for humans to go it has the
advantage over Mars of being a much nearer place to learn how to set
up and live in a base on another world. Then there is the potential for
mineral resources and astronomical observatories.
