Where in the Bible does it say that the Earth is the only place in the universe that God created life? Why would finding life on Mars automatically mean that people shouldn't believe the Bible?
First off, the original planet with 'life' on it was not Earth (as we know it now). Mars is a leftover of a collision between the original life-bearing planet and a planet from another solar system/galaxy.
Many of the 'dead' moons are also leftover particles as well as most of the asteroid belts. Our moon is one of the leftover particles as well.