To practical, rational man, it is the Xanthe Desert. Whatever else he might unwittingly be, S. Nuwell Eli considered himself a practical, rational man, and it was across the bumpy sands of the Xanthe Desert that he guided his groundcar westward with that somewhat cautious proficiency that mistrusts its own mastery of the machine. Maya Cara Nome, his colleague in this mission to which he had addressed himself, was a silent companion. Nuwell's liquid brown eyes, insistent upon their visual clarity, saw the red sand as the blowing surface of unliving solidity. Only clarity was admitted to Nuwell, and the only living clarity was man and beast and vegetation, spotted in the dome cities and dome farms of the lowlands. He and Maya scurried, transiting sparks of the only life, insecure and hastening in the absence of the net of roads which eventually would bind the Martian surface to human reality from the toeholds of the dome cities. In that opposite world which was the other side of the groundcar's seat, Maya Cara Nome's opaque black eyes struggled against the surface. They struggled not from any rational motivation but from long stubbornness, from habit, as a fly kicks six-legged and constant against the surface tension of a trapping pool. Formally, Maya was allied to Newell's clarity and solidity, and she could express this alliance with complete logic if called on. But behind the casually blowing sand she sensed a depth. The shimmering atmosphere, hostile to man, which sealed the red desert was a lens that distorted and concealed by its intervention. The groundcar was a mechanical bug, an alienness with which timorous man had allied himself; allied with it against reality, she and Nuwell were hastened by it through reality, unseeing, toward the goal of a more comfortable unreality. The groundcar bumped and slithered, and an orange dust-cloud boiled up from its broad tires and wafted away across the sculpted sand. The desert stretched away, silent and empty, to the distant horizon; the groundcar the only humming disturbance of its silence and emptiness. The steel-blue sky shimmered above, a lens capping the red surface. The groundcar rolled westward, slashing toward its goal from the distant lowland of Solis Lacus. Far away, two men, machineless, plodded this same Xanthe Desert toward the same goal; but they plodded southward, approaching on a different radius. They were naked. In a thin atmosphere without sufficient oxygen to support animal life or even the higher forms of terrestrial plant life, they wore no marsuits, no helmets, no oxygen tanks. The man who walked in front was tall, erect, powerfully muscled. His features and short-clipped hair were coarse, but self-assured intelligence shone in his smoky eyes. He moved across the loose sand, barefoot, with easy grace.