If there had been any humor in the situation before, it was gone now utterly! The patrol man's lips dropped apart in sheer awe. The muscles of his massive, freckle-smeared forearms tightened futilely as he longed to help the X911's doomed pilot. In the pit of his stomach there was a sickish feeling.
Where that rocket that had dared the inscrutable enigma of the Forbidden Moon had been, there was a sudden, terrific blaze of light. The intolerable incandescence of it seemed to reach out to infinity itself, illuminating even the blackness between the distant stars of space. But it was all as silent as the bouncing of a bubble on velvet. No explosion, however huge, can transmit sound in the emptiness of the void.
The magnificent, horrible blast broke into a million gobs and sparks of molten metal—from what had once been a space ship's hull. Superheated gas from ignited rocket fuel shot out. Scattered far and wide, the white-hot fragments of the wreck continued on their way, following the original direction of the once bold X911 toward Io. Their speed increased gradually, as the gravity of the Forbidden Moon pulled them. The larger chunks, falling at meteoric speed, would bury themselves deep in the cold Ionian deserts.
The secret of Io had claimed another victim, one who might have been victorious. But Io's mystery was still unviolated. Evan Harwich had seen other ships, disabled and unmaneuverable for some reason beforehand, go to their ends like this; but he was still not used to the spectacle, and to the unholy wonder it provoked in him.
Dazzled and almost blinded, he guided his patrol boat shakily away from the Forbidden Moon. There was cold sweat in his thick, black hair, under his leather helmet; and cold sweat too on his narrow, bristly cheeks. His movements of the controls were a trifle vague and fumbling with emotion, making his patrol boat waver a little in its course.
For perhaps the millionth time Harwich wondered: "What makes Io so dangerous? Dammit all, those scientists who claim that there is a deadly shell of unseen energy completely enveloping the Forbidden Moon, must be right! There isn't anything else that could explain the continual destruction of all rocket craft that come within that five-thousand-mile limit!"
Evan Harwich was ready to accept this much as fact. But beyond this, there was still a vast, unguessable question mark.
Was this shell of energy a natural phenomenon; or was it something planned, made, intended for a purpose? If the latter guess was right, who could have created such a gigantic screen of force? What kind of beings? What kind of science?
Io was an almost dead world, Harwich knew. Very cold. Very little water and air. Astronomers had taken photographs of its terrain through powerful telescopes, from the other moons of Jupiter. Very little could be seen on those photographs but deserts and grey hills, and curious formations which might be the magnificent ruins left by an extinct race.
Evan Harwich was far from a weakling; but cold chills were playing over his big body as he groped to understand the unknown.