Jekyll-Hyde Planet

Centifor was a paradise planet, another Garden of Eden. And Leon Stubbs was the serpent of temptation....
They came in low, decelerating against dense air, while the passengers talked, and laughed, and pressed their faces against the observation ports.
In the ship's lounge, a squawk box crackled ... Twenty minutes, a mechanical voice said ... We land on Centauri IV in twenty minutes ... Passengers for Orion, Antares, Cygni, and Polaris, have your transfers ready.
Everyone laughed. The speaker clicked and went dead. And the boy who'd been gripping Claude Marshall's arm looked up.
What's he mean, Pop? We don't really have to transfer, do we?
Claude Marshall smiled. No, Billy. This is as far as we're going—as far as anyone's going.
But he said—
He was only joking, Billy. Maybe someday people will be going to those places, but not now. He glanced at his wife, sitting with her hands folded in her lap.... I'm glad it's over, Joan, he said. It's been a long trip—a very long trip.
The woman nodded. She had dark hair, and blue eyes, and minute lines of maturity around her eyes and mouth that seemed to soften, rather than age her. She looked almost too young to have mothered a nine-year-old boy—but of course that was one of the requirements.
Is this where we're going to live? the boy asked.
Claude looked out the port. Yes, Billy. This is where we're going to live.
Why?