I am not addressing flying saucer stuff.
I don’t think this topic includes it either.
No scientist who argues for other inhabitable worlds uses UFO stories as evidence.
That’s really a different topic.
Okay then, how about a scene from Daniel Chapter five. There was a hand, a human looking hand, which wrote upon the wall of palace party central, in the visual range of King Belshazzar. All that was in the coordinate system of Belshazzar was the hand. The rest of that being was 'extra-terrestrial', standing in a completely different coordinate zone. There is life in that zone and it is not the same region as the King of Babylon, so it is 'extra-terrestrial.
The difficulty is how we define 'life arisen'. God created the entire shebang, including all the coordinate systems. We really don't know what is in the coordinate systems not accessible to our 'science' at the limits of our current Physics.