Glory comes from a job well done. You'll experience the thrill of experimentation and exploration—even when you're doing mundane things like examining how a plant reacts to zero gravity and testing the parachute on the landing pod. You're a small but important part of the grand mission of human exploration, following in the footsteps of the greatest explorers of history.
Well, you probably won't actually step your foot onto anything yourself, but eventually someone, somewhere, will put a foot on Mars. It's the glory of the journey—although the destination isn't bad either.