I have not studied enough other religions to determine whether or not they teach that God only made life here on earth.
I do not think it is impossible that there is life elsewhere. I am convinced that at the very least there is plant life, and perhaps some animals on some of the other trillions of planets in the universe.
I find it hard to believe that the earth is the only planet that can sustain life. Who knows?? Maybe part of heaven is visiting these other planets??
That being said, I don't think we will ever see aliens on our planet in our lifetime. At least not that is depicted in the movies and tv.