"Where do Christians stand on whether or not we are the only inhabited planet in the universe?"
We should prepare for war against the planet Mars. Why do you think it's named after the "god" of war. /sarcasm
Personally, I think the universe is mankind's playground. The stars are just pin pricks of light for use to use as celestial navigation. I view any spiritual and intelligent creature outside the human race with great suspicion until it's determined that it's "of God". E.T. is the devil. T.I. from the abyss is the devil. The Virgin and the Eucharist is our pillars to moor our ship.