Cave-Dwellers of Saturn

Across Earth's radiant civilization lay the death-shot shadows of the hideous globe-headed dwarfs from Mars. One lone Earth-ship dared the treachery blockade, risking the planetoid peril to find Earth's life element on mysterious Saturn of the ten terrible rings.
It was a crisp, clear morning in the city of Copia. A cold winter's sun glinted on the myriad roof tops of the vast spreading metropolis. To the north, snow-covered hills gleamed whitely, but the streets of Copia were dry and clean. There were not many people stirring at such an early hour. The dozen broad avenues which converged like the spokes of a great wheel on Government City in the center of Copia were quite deserted. There was little apparent activity around and about the majestic Government buildings, but the four mammoth gates were open, indicating that Government City was open for business.
At the north gate the sentry, sitting behind his black panel with its clusters of little lights, switches, and push-buttons, glanced upward. There was a faint humming and a man was circling downward about a hundred feet above him. The rays of the early sun flashed off a helmet and the sentry knew that this man was a soldier. The newcomer dropped rapidly, the stubbed wings on his back a gray blur. Then the humming ceased as the soldier switched off his oscillator and landed lightly on the ground before the sentry.
The sentry's swift glance took in the immensely tall, broad-shouldered figure, covered to the ankles in the green cloak. He took in also the pink, smiling face and merry blue eyes, and the lock of bright red hair which showed as the soldier pushed his helmet backward off his forehead.
Your business? asked the sentry.
I have orders to report to the Commander-in-Chief, said the soldier, with a pleasant smile.
Let's see, said the sentry, glancing at the insignia on the helmet, you're a decurion of the Eightieth Division. And the name?
Dynamon, said the soldier.
Oh, yes, said the sentry, with a recollective smile, I remember you as an athlete. Didn't I see you in the Regional Games two years ago?