This story, from Mysteries of Unexplored Worlds #16, starts off quite dully.
It's so dull, in fact, that I'm starting with an image from the second page. Don't worry, the first page was so boring that nothing of importance or significance happened on it.
Some guy has taken a rocket out to the vicinity of Jupiter in hopes of investigating it. Since he can't land on the gas giant, he'll land on Ganymede.
He lands, tests the atmosphere, and if this story wasn't failing some field or another forever, he would have died instantly.
He takes a look around, and...
Don't worry, it gets better... sort of.
He sees some togas on a clothesline, and decides it's time for a disguise.
He's wandering around when...
Not so much hideous as incredibly dorky beings approach.
They find him... curiously exciting.
He decides to escape, seeing as how the beings who have captured him are huge, have incredibly short legs, and probably could be outpaced by a toddler. One of the workers grabs him, and he punches the man out, only to discover...
... This guy must read Arthur C. Clarke or something.
Who built the robots? A good question indeed. But he jumps to yet another conclusion:
You explored like two miles of the planet's surface. How do you know that there wasn't a real settlement of less humanlike people over the next ridge? Or that perhaps the big robots were actually life support suits or transportation? Or that they were actually invaders from another solar system?
Just because they're on Jupiter's moon doesn't mean they have a blooming thing to do with Jupiter.
My favorite part of this story has to be the weird can robot/creatures; otherwise, it's kind of forgettable.