The nutrition packs are low-residue, but every few days you must still squat for nature. Your life support can’t recycle solid waste, so you wait for the suit to desiccate the waste and then void the crumbly brown powder to vacuum. Your trail is marked by your powdery deposits, scarcely distinguishable from the dark lunar dust.

Walk west, ever west, racing the sun.

Earth was high in the sky; she could no longer see it without craning her neck way back. When the Earth was directly overhead she stopped and celebrated, miming the opening of an invisible bottle of champagne to toast her imaginary traveling companions. The sun was well above the horizon now. In six days of travel she had walked a quarter of the way around the moon.

She passed well south of Copernicus, to stay as far out of the impact rubble as possible without crossing mountains. The terrain was eerie, boulders as big as houses, as big as shuffle tanks. In places the footing was treacherous where the grainy regolith gave way to jumbles of rock, rays thrown out by the cataclysmic impact billions of years ago. She picked her way as best she could. She left her radio on and gave a running commentary as she moved. “Watch your step here, footing’s treacherous. Coming up on a hill; think we should climb it or detour around?”

Nobody voiced an opinion. She contemplated the rocky hill. Likely an ancient volcanic bubble, although she hadn’t realized that this region had once been active. The territory around it would be bad. From the top she’d be able to study the terrain for a ways ahead. “Okay, listen up, everybody. The climb could be tricky here, so stay close and watch where I place my feet. Don’t take chances better slow and safe than fast and dead. Any questions?” Silence; good. “Okay, then. We’ll take a fifteen minute break when we reach the top. Follow me.”

Past the rubble of Copernicus, Oceanus Procellarum was smooth as a golf course. Trish jogged across the sand with a smooth, even glide. Karen and Dutchman seemed to always be lagging behind or running up ahead out of sight. Silly dog still followed Karen around like a puppy, even though Trish was the one who fed him and refilled his water dish every day since Karen went away to college. The way Karen wouldn’t stay close behind her annoyed Trish. Karen had promised to let her be the leader this time—but she kept her feelings to herself. Karen had called her a bratty little pest, and she was determined to show she could act like an adult. Anyway, she was the one with the map. If Karen got lost, it would serve her right.

She angled slightly north again to take advantage of the map’s promise of smooth terrain. She looked around to see if Karen was there, and was surprised to see that the Earth was a gibbous ball low down on the horizon. Of course, Karen wasn’t there. Karen had died years ago. Trish was alone in a spacesuit that itched and stank and chafed her skin nearly raw across the thighs. She should have broken it in better, but who would have expected she would want to go jogging in it?

It was unfair how she had to wear a spacesuit and Karen didn’t. Karen got to do a lot of things that she didn’t, but how come she didn’t have to wear a spacesuit? Everybody had to wear a spacesuit. It was the rule. She turned to Karen to ask. Karen laughed bitterly. “I don’t have to wear a spacesuit, my bratty little sister, because I’m dead. Squished like a bug and buried, remember?”

Oh, yes, that was right. Okay, then, if Karen was dead, then she didn’t have to wear a spacesuit. It made perfect sense for a few more kilometers, and they jogged along together in companionable silence until Trish had a sudden thought. “Hey, wait—if you’re dead, then how can you be here?”

“Because I’m not here, silly. I’m a fig-newton of your overactive imagination.”

With a shock, Trish looked over her shoulder. Karen wasn’t there. Karen had never been there.

“I’m sorry. Please come back. Please?”

She stumbled and fell headlong, sliding in a spray of dust down the bowl of a crater. As she slid she frantically twisted to stay face-down, to keep from rolling over on the fragile solar wings on her back. When she finally slid to a stop, the silence echoing in her ears, there was a long scratch like a badly healed scar down the glass of her helmet. The double reinforced faceplate had held, fortunately, or she wouldn’t be looking at it.

She checked her suit. There were no breaks in the integrity, but the titanium strut that held out the left wing of the solar array had buckled back and nearly broken. Miraculously there had been no other damage. She pulled off the array and studied the damaged strut. She bent it back into position as best she could, and splinted the joint with a mechanical pencil tied on with two short lengths of wire. The pencil had been only extra weight anyway; it was lucky she hadn’t thought to discard it. She tested the joint gingerly. It wouldn’t take much stress, but if she didn’t bounce around too much it should hold. Time for a break anyway.

When she awoke she took stock of her situation. While she hadn’t been paying attention, the terrain had slowly turned mountainous. The next stretch would be slower going than the last bit.

“About time you woke up, sleepyhead,” said Karen. She yawned, stretched, and turned her head to look back at the fine of footprints. At the end of the long trail, the Earth showed as a tiny blue dome on the horizon, not very far away at all, the single speck of color in a landscape of uniform grey. “Twelve days to walk halfway around the moon,” she said. “Not bad, kid. Not great, but not bad. You training for a marathon or something?”

Trish got up and started jogging, her feet falling into rhythm automatically as she sipped from the suit recycler, trying to wash the stale taste out of her mouth. She called out to Karen behind her without turning around. “Get a move on, we got places to go. You coming, or what?”

In the nearly shadowless sunlight the ground was washed-out, two-dimensional. Trish had a hard time finding footing, stumbling over rocks that were nearly invisible against the flat landscape. One foot in front of the other. Again. Again.

The excitement of the trek had long ago faded, leaving behind a relentless determination to prevail, which in turn had faded into a kind of mental numbness. Trish spent the time chatting with Karen, telling the private details of her life, secretly hoping that Karen would be pleased, would say something telling her she was proud of her. Suddenly she noticed that Karen wasn’t listening; had apparently wandered off on her sometime when she hadn’t been paying attention.

She stopped on the edge of a long, winding rille. It looked like a riverbed just waiting for a rainstorm to fill it, but Trish knew it had never known water. Covering the bottom was only dust, dry as powdered bone. She slowly picked her way to the bottom, careful not to slip again and risk damage to her fragile life-support system. She looked up at the top. Karen was standing on the rim waving at her. “Come on! Quit dawdling, you slowpoke—you want to stay here forever?”

“What’s the hurry? We’re ahead of schedule. The sun is high up in the sky, and we’re halfway around the moon. We’ll make it, no sweat.”

Karen came down the slope, sliding like a skier in the powdery dust. She pressed her face up against Trish’s helmet and stared into her eyes, with a manic intensity that almost frightened her. “The hurry, my lazy little sister, is that you’re halfway around the moon, you’ve finished with the easy part and it’s all mountains and badlands from here on, you’ve got six thousand kilometers to walk in a broken spacesuit, and if you slow down and let the sun get ahead of you, and then run into one more teensy little problem, just one, you’ll be dead, dead, dead, just like me. You wouldn’t like it, trust me. Now get your pretty little lazy butt into gear and move!”