The towers of Titan

Across the frozen cliffs they loomed—the unbelievably ancient towers with the unimaginable engines deep inside them still pouring out their endless power. Dr. Sidney Lee, back from living death, vowed to find the secret of ...
By BEN BOVA
Illustrated by EMSH
The landing port at Titan had not changed much in five years.
The ship settled down on the scarred blast shield, beside the same trio of squat square buildings, and quickly disgorged its scanty quota of cargo and a lone passenger into the flexible tube that linked the loading hatch with the main building.
As soon as the tube was disconnected, the ship screamed off through the murky atmosphere, seemingly glad to get away from Titan and head back to the more comfortable and settled parts of the Solar System.
The passenger, Dr. Sidney Lee, stood by the window-wall of the main building and watched the ship disappear into the dark sky. He was tall and lean, seemingly all bone and tendon, with graying dark hair and faintly haunted eyes set deep into a rough-hewn, weather-worn face. When the ship was nothing more than another star overhead, he turned and looked at the place.
Five years hasn't made any difference , he thought. The single room of the main port building was unchanged: a little grimier, perhaps, and a little more worn. But essentially unchanged. There were the same turnstiles and inspection machines, the same processing and handling gadgets for your papers and baggage, the same (it couldn't be, but they looked the same) two bored techs sitting at the far end of the room, unwilling to lift an eyebrow unless specifically commanded to do so.
Lee walked over to the papers processor and pushed his credentials into its slot. After a few wheezes and clanks its green light flickered on and the papers fell into the return bin properly stamped and approved. At the same time, his lone bag slid along a conveyor belt and onto the pickup table.
With his credentials back inside his jacket and the bag in hand, Lee looked toward the two clerks. They were studiously avoiding his eyes, searching intently through some schedules that they kept on hand for just such emergencies.