From Dr. Tom Woodward:

We've previously talked about C.S. Lewis' previous use of quarantine in his essays on outer space in his book on a "trip to Venus", "Perelandra."  Here's another, in "Religion and Rocketry" (the concluding piece in "The World's Last Night and Other Essays"):

"I have wondered before now whether the vast astronomical distances may not be God's quarantine precautions. They prevent the spiritual infection of a fallen species from spreading." 

This micro-snippet is a concluding thought in this fascinating essay that asks, "Are there other life forms in space and what are the implications for the serious Christian?" Highly recommended!