Mel Gray flung down his hoe with a sudden tigerish fierceness and stood erect. Tom Ward, working beside him, glanced at Gray's Indianesque profile, the youth of it hardened by war and the hells of the Eros prison blocks. A quick flash of satisfaction crossed Ward's dark eyes. Then he grinned and said mockingly. "Hell of a place to spend the rest of your life, ain't it?" Mel Gray stared with slitted blue eyes down the valley. The huge sun of Mercury seared his naked body. Sweat channeled the dust