For months the sturdy robot surveyor had been picking its way along the rim of the Valles Marineris, sending its broadcasts. Lindsay sat with his back to the mighty chasm: its titanic scale and air of desolate, lifeless age had painful associations for him. The rubble and foothills projected on the rounded wall before him, huge upthrust blocks and wind-carved yardangs, struck him as an implied reproach. It was new to him to have a sense of responsibility for a planet. After three months in C-K, he was still trying the dream on for size.