There is nothing new under the sun. I thought that perhaps my speculations about space and other worlds would be new, but I am already finding evidence that this topic has been much thought of from of old. Here is Melancthon saying that there cannot be inhabitants on other planets:
We know God is a citizen of this world with us, custodian and server of this world, ruling the motion of the heavens, guiding the constellations, making this earth fruitful, and indeed watching over us; we do not contrive to have him in another world, and to watch over other men also…the Son of God is One; our master Jesus Christ was born, died and resurrected in this world. Nor does He manifest Himself elsewhere, nor elsewhere has He died or resurrected. Therefore, it must not be imagined that there are many worlds, because it must not be imagined that Christ died and was resurrected more often, nor must it be thought that in any other world without the knowledge of the Son of God, that men would be restored to eternal life.
[Initia doctrinae physicae] quoted in Steven J. Dick, Plurality of Worlds, p. 89
The uniqueness of the incarnation here on earth is a central concern of many who say that there cannot be humans on other planets.