Note: The worlds visible at the right edge of the first panel are Earth and Luna. Earth is the little one with the ring -- it appears smaller because it's more distant, and it has a visible ring because there is a lot of material in close orbit around it. Luna, on the other hand, is a blue-green marble instead of an airless desert because humans worked very hard to make it a nicer place to live in spite of the environmental concerns.
"What environmental concerns?" you ask. "Nothing lived there!" True, but environmentalists were concerned that terraforming the moon would alter its night-time appearance to the eternal, species-extinguishing confusion of a number of insects, migratory birds, and ballad-writers. And in truth, the gloriously beautiful jewel the moon became still failed to compete with Earth's city lights, let alone the amber, equatorial glow of Earth's ring. Fortunately, new species arose and used that arch across the heavens for better night-vision, as a navigational tool, or as a cue to go misty-eyed just before the reprise.