Driscoll is the Johnny Appleseed of Mars, only with a motorcycle and a slight habit of fainting. He faints when he gets to Mars because the air is so low in oxygen. Then at the end of the story, when all his trees start to put out oxygen, he faints again.
Hm, sounds like there might be a moral here about excess.
When Driscoll arrives on Mars, he looks around and asks himself a question: "How do I fit here? What will I do? Is there a job for me?" (8). And he finds it—planting trees all over the world.
No one tells Driscoll to do this. That's what's kind of cool: he just sees something that he thinks needs to be done, and he does it. This seems to be something Bradbury admires. You get the sense that he's a little fed up with bureaucracy and government and regulations.
But notice that Driscoll is… unusual. He's putting seeds into the soil, which is the opposite of what everyone else is doing on Mars. The town coordinator points out that the first settlements on Mars are mining communities—people taking things out of the ground. Just like Bradbury's other protagonists, Driscoll is a guy who doesn't quite fit in.