The main idea here is that evolutionism and a belief in "aliens" travel together.
A person who believes in evolution has to believe that any other living world he might find out there would have to be totally different from ours since it would have evolved along totally different lines. I used to read a lot of scify novels as a teenager and many if not most of them described aliens with some totally different organic basis, e.g. silicon instead of carbon, and something other than the DNA/RNA scheme as a chemical basis. But that is not what is actually turning up. What actually turns up is very much more like what a Christian or some other religious person would anticipate. The two places in our system other than Earth that are interesting are Mars and Ganymede and on both of those places, we see evidence of past habitation by creatures such as we are entirely familiar with, exactly as if the same basic plan for living worlds had been used for all three places. That is the way you'd expect God to work. Mars remains minimally inhabited. You've seen the image of the little ground squirrel on Mars that went viral on the Internet a few years ago, but it has gotten better than that since then. For instance...
That is a NASA/JPL Mars rover image, i.e. the little girl lives on Mars. The picture is blurry since it was snapped from a quarter mile away more or less; it not having been possible to get the rover closer than that over rough ground. The girl is holding a large dog like a goldie or collie, and the legs you see are the dog's legs draped over the girl's lap.
The story
Latest edition of my book describing all of that sort of thing.
Jupiter and Ganymede were much closer to the sun in the ages in which Ganymede was inhabited. Ganymede is a frozen wasteland now and I can't picture anything still living there.