"Almost done," Nadia declared late in the day, as she started to bolt the transport pipe onto the last magnesium post.  Her hands were dangerously cold, and her maimed hand throbbed.  "Maybe someone could start dinner," she said.  "I'm almost done here."  The transport pipe had to be packed in a thick cylinder of white polyurethane foam, then fitted into a larger protective pipe.  Amazing how much insulation complicated a simple piece of plumbing.

Hex nut, washer, cotter pin, a firm tug on the wrench. Nadia walked along the line, checking the coupling bands at the joints.  Everything firm.  She lugged her tools over to Rover One, looked back at the result of the day's work:  a tank, a short pipe on posts, a box on the ground, a long low mound of disturbed soil running uphill, looking raw but otherwise not unusual in this land of lumps.  "We'll drink some fresh water on our way back," she said.

# # #

They had driven north for over two thousand kilometers, and finally rolled down onto Vastitas Borealis, an ancient cratered lava plain that ringed the northern hemisphere between latitudes 60° and 70°.   Ann and the other geologists spent a couple of hours every morning out on the bare dark rock of this plain, taking samples, after which they would drive north for the rest of the day, discussing what they had found.  Ann seemed more absorbed in the work, happier.  One evening Simon pointed out that Phobos was running just over the low hills to the south; the next day's drive would put it under the horizon.  It was a remarkable demonstration of just how low the little moon's orbit was; they were only at latitude 69°!   But Phobos was only some five thousand kilometers above the planet's equator.  Nadia waved goodbye to it with a smile; she would still be able to talk to Arkady using the newly arrived areosynchronous radio satellites.

Three days later the bare rock ended, running under waves of blackish sand.  It was just like coming on the shore of a sea.  They had reached the great northern dunes, which wrapped the world in a band between Vastitas and the polar cap; where they were going to cross, the band was about eight hundred kilometers wide.  The sand was a charcoal color, tinged with purple and rose, a rich relief to the eye after all the red rubble of the south.  The dunes trended north and south, in parallel crests that occasionally broke or merged.  Driving over them was easy; the sand was hard-packed, and they only had to pick a big dune and run along its humpbacked western side.