 Why was there fear for the wind shifting around the Hairy People?
But here in the cavern world, thirty-seventh in the linked series of vast caves that underlie the waterless wastes of Mars, the reflected waves of sound were of little value. They know these caverns better than.... That was old Garmon Nash, his fellow patrolman aboard the Planet Patrol ship as he swung the deadly slimness of his rocket blast's barrel around to center on the fiery jets that betrayed the approaching outlaw flyers. Rolf swung the lax controls over hard as the bursts of fire revealed a looming barrier of stone dead ahead, and then he felt the tough skin of the flyer crumple inward. Their mad speed checked momentarily, but the nose of the vertically plunging ship dissolved into an inferno of flame. There could be no ascent from this natural prison-pit, and even if there were he could never hope to reach the surface forty miles and more overhead. The floors of the thirty-seven caves through which they had so carefully jetted were a splintered, creviced series of canyon-like wastes, and as he ascended the rarefied atmosphere of the higher levels would spell death. Without water and food certain death grinned in his face, for beyond the sand-buried entrance to these lost equatorial caves there were no pressure domes for hundreds of miles. Here at least the air was thick enough to support life, and somewhere nearby the outlaws who smuggled their precious contraband water into the water-starved domes of North Mars lay hidden. Half of the oval bar he crushed between his teeth, and when the concentrated energy flooded into his muscles he set off around the irregular wall of the pit. The outlaw headquarters might be close ahead, headquarters where renegade Frogs, Venusians from the southern sunken marshes of Mars, and Earthmen from dusty North Mars, concealed their precious hoard of water from the thirsty colonists of North Mars. Then the light brightened before him as he rounded a shouldering wall of smoothly trimmed stone, and the floor fell away beneath his feet! Toward this barrier the spinner bore him, and Rolf was content to let it move in that direction—from the heights of the wall he could scout out the country beyond. The wall expanded as he came nearer to the pygmy planet. The spinner had slowed its speed; it seemed to Rolf that he must be falling free in space for a time, but the feeble gravity of the tiny world tugged at him more strongly as he neared the wall. And the barrier became a jumbled mass of roughly-dressed stone slabs, from whose earth-filled crevices sprouted green life.
 The wind would spread the scent of the Earthmen and cause an attack
 They wind would block the mind reading abilties of the Hairy People.  The wind would cause explosions.  The wind would spread the hair from the Hairy People and block vision.  The wind would spread the scent of the Earthmen and cause an attack