Lucky Starr And The Moons of Jupiter

Sabotage!!! Agrav. It was the century's most important advance in space travel. . . and an experiment so revolutionary that only the men who huddled beneath the surface of Jupiter Nine were permitted to know its full meaning. Yet someone else did know--knew everything, saw everything, head everything--and was diabolically sabotaging the top-secret mission. Who or what the enemy was, Lucky Starr didn't know. but one thing was certain. The deadly force was not human. . . not even remotely human!