The Metal Moon

In this story, the joint product of two imaginative minds, we get a very unusual picture of some of the possibilities of interplanetary exploration. We know that as soon as interplanetary travel is possible, expeditions from the earth will be ranging the length and breadth of the solar system searching out the thousands of wonders that are to be discovered. It is quite possible that some of the explorers, whether through accident or desire, may colonize the other planets and develop under new and unusual conditions a new branch of the human race. It is doubtlessly true that if each of the solar planets were to be colonized, at the end of several hundred centuries there would be nine races of human beings who might differ radically from each other and in fact might not recognize each other as members of the same human stock. In this story we do not see nine races but we do see four of them and Mr. Starzl has united the four in a gripping narrative of the great spaces.
The three men in the tiny space ship showed their apprehension as they watched the gravity meters. Something was distinctly wrong with the ship.
Are you sure that there isn't some undiscovered moon of Jupiter? asked the youngest of them. He was only about 25, which was very young indeed when his scientific attainments were considered, even for the human race's stage of intellectual development in 1,000,144 A. D. His figure was stocky, powerful, his face rather thin, bold, with piercing black eyes. He was naked, save for short, brilliantly red trunks of metalsilk. His name, Sine, followed by a numerical identification code, was tattooed indelibly in thin, sharp characters on his broad, bronze-hard chest.
The man at the ampliscope removed his head from the eyepiece and shook his head impatiently. His body was bronzed and spare, but the complete absence of hair on his head made him look older than the 48 years indicated by the code following the name on his chest, Kass.
I tell you, Sine, this pull is no gravity effect. No body of such mass could be invisible, unless it were composed entirely of protons. And even then it would yank Jupiter out of shape, making it look like a pear, but there—