The new trail occupied angled cracks in the blocky cliff wall, the steps fitted like the pieces of a jigsaw puzzle, and very regular, so that it was like running down a staircase in the ruined wall of some giant’s castle. Cliffside trailmaking was an art, a lovely form of work that Nirgal had joined from time to time, helping to move cut rocks with a crane, to wedge them into position on top of the step below— hours in a belay harness, pulling on the thin green lines with gloved hands, guiding big polygons of basalt into place. The first trail builder Nirgal had met had been a woman constructing a trail along the finback of the Geryon Montes, the long ridge on the floor of Ius Chasma. He had helped her all of one summer, down most of the ridge. She was still in Marineris somewhere, constructing trails with her hand tools and high-powered rock saws, and pulley systems with superstrong line, and glue bolts stronger than the rock itself— painstakingly assembling a sidewalk or staircase from the surrounding rock, some trails like miraculously helpful natural features, others like Roman roads, others still with a pharaonic or Incan massiveness, huge blocks fitted with hairline precision across boulder slopes or large-grained chaos.

Down three hundred steps, counting, then across the sink floor in the hour before sunset, the strip of sky a velvet violet glowing over dark cliff walls. No trail here on the shadowed sand of the sink floor, and he focused on the rocks and plants scattered over it, running between things, his glance caught by light-colored flowers on top of round-barreled cacti, glowing like the sky. His body was also glowing, with the end of the day’s run, and the prospect of dinner, his hunger a gnawing from within, a faintness, getting more unpleasant by the minute.

He found the staircase trail on the western cliff wall, up and up, changing gears into the uphill push stride, smooth and regular, turning left and right with the switchbacks, admiring the elegant placement of the trail in the crack system of the cliff, a placement that usually had him running with a waist-high wall of rock on the air side, except during the ascent of one bare sheer patch of rock, where the builders had been forced to the extremity of bolting in a solid magnesium ladder. He hurried up it, feeling his quadriceps like giant rubber bands; he was tired.