I was completely confused by the question of silicone based life forms, rather than carbon. Surely the 'how' is not that important as God managed to create the entire universe out of nothing.
I think we need to ask ourselves a few questions to get an idea of whether the idea of alien life forms is possible, taking the Bible as our basis. Before I go on I know this is not going to answer the arguments from you atheists, but I am concentrating on the Christians first!!!!
Right, questions:
How many gods are there? Is Jesus God? Did he come to the earth to redeem his people after Adam fell? What did Jesus' death accomplish?
I believe in One God. I believe Jesus came to this earth to die for the sins of mankind so we can have peace with him and go to heaven.
In Romans 8 it talks about the whole of creation groaning because of sin. I take that to mean everything, all the galaxies, universes, stars, all that is out there.
If alien life forms are purely basic micro-organisms this point is irrelevant. However, if alien beings are advanced, with never dying souls capable of knowing God, what would happen to them? Christ died for all mankind but does that mean he had to go to another planet to preach to aliens and die for them? Aliens would live under the same curse as the rest of creation caused by Adam's fall.
My answer would be no to Christ going through it all for another group of creatures. Though we are a tiny speck in the universe, Jesus is Almighty God and surely he would only need to die once. I hope no-one would seriously consider that Jesus had to take on alien-flesh.
Am I making sense? Possibly not.
In short I don't think the Bible allows for alien life forms. It is a mystery but God created mankind for his pleasure, we appear to be pivotal to creation. This is not to make us big headed but to bow down and worship God who in his infinite wisdom made things this way.
Needless to say, I believe in a literal six-day creation so I have no idea whether my arguments could be countered by a belief in theistic evolution.