Invaders of the Forbidden Moon

Annihilation was the lot of those who ventured too close to the Forbidden Moon. Harwich knew the suicidal odds when he blasted from Jupiter to solve the mighty riddle of that cosmic death-trap.
Calling the pilot of space ship X911! Evan Harwich shouted into the radio transmitter of his little Interplanetary Patrol Boat. Good God! Turn your crate back, you crazy fool! Don't you know you're headed right into the danger zone of Jupiter's Forbidden Moon? You'll get yourself burned to a crisp in another few seconds if you don't turn back....
Evan Harwich's growling voice was almost shrill at the end. His police duties patrolling the vicinity of Io, innermost of Jupiter's larger satellites, rarely developed moments as tense as this. Most other pilots had brains enough to give the Forbidden Moon a wide berth. And for excellent if mysterious reasons!
Yet the craft ahead, a sleek new job with the identification number X911 painted on its conning tower, kept steadily on. Its slim hull, which betrayed an experimental look, was pointed straight at the threatening greyish disc of Io, the one world in the solar system which no exploring ship of the void had ever reached—intact!
Almost everybody among the inhabited spheres knew about the dangers of the desolate Forbidden Moon. Ever since the colonial empire of Earth had been extended to the region of Jupiter and his numerous satellites, Io had been a grim menace; sure destruction to any rocket that approached within five thousand miles of its dreary, almost airless surface.
Nobody seemed to know just why this was true; but some scientists claimed that somehow there was an invisible layer or shell all around Io; an immense blanket of strange energy or force that fused and blasted the metal hulls of all ether craft that ran into its insidious web.
Tensely and helplessly Evan Harwich watched, as the ship ahead continued on its way toward what seemed sure catastrophe. No danger in front of the recklessly piloted craft could be seen, of course. Five thousand miles of clear, cold vacuum was all that was visible between it and Io. But since this region held concealed in it all the potential violence of a hair-triggered trap, ready to unleash a flaming death that involved unknown physical laws and principles, maybe it wasn't just plain vacuum after all!