Humanity had spread. The people on Mars and Luna were in constant contact, sharing the progress and discoveries they were making, and occasionally sending ships back and forth. The cultures of the two worlds were quite different, however.

The Selenites (as they called themselves. Martians referred to them affectionately as Loonies) were generally quiet, slender, and thoughtful. Their world was largely underground due to the harsh differences between day and night on the surface, but the excavations that housed the lunar colonies were expansive and well appointed. The old, narrow tunnels were almost nowhere to be seen, replaced over centuries by broad corridors, well lit and well ventilated. The nexii where two or more corridors came together were traditionally large bowls with glass domes that looked out on the sky above, albeit with some shielding during the daylight weeks. Green grass and trees grew in the nexii, large, sprawling parks at the center of the bowls. The terraced sides were different, with various artistic and natural formations, either truly selenian formations or copies of the most beautiful parts of Earth. Waterfall Park, one of the newest nexii, was an example of how the two blended beautifully.

A waterfall isn’t something that would ever happen naturally on the moon, of course. For that matter it was only recently that Luna had enough water to allow it to exist now. But a waterfall as beautiful as this one would never occur on earth, either. The reason that Waterfall Park is beautiful and mesmerising is obvious if you think about it.

The gravity on the moon is 1/6th that of earth. That means that the water falls in a leisurely column, twisting and taking its time to reach the bowl below. When it lands it strikes with much less force than it would do on Earth. Drops that jumped up out of the bowl flew higher, fell slower, and were small, beautiful crystals that you could watch for hours, if you didn’t have anywhere to go. Lights from behind the waterfall accentuated the prismatic effects of the water, scattering light in all colors all over the nexus, sparks and glints of color flashing across the face of the person with whom you were strolling. Some bowls were meant for gathering and discussing politics or transacting business. This nexus was for restoring the soul.

Kaylee and Isadora were sitting on one of the benches, looking at the waterfall, occasionally catching the small droplets that flew out close to them. They were laughing and happy and content with life. They had just graduated high school. Selenite custom allowed for a few years between the end of high school and the beginning of college for people to get some perspective and decide what they wanted to do with their lives, and those glorious, free years stretched ahead of the pair of friends.

Kaylee lay her head in Isadora’s lap and looked through the dome above the bowl. Earth was rising and she observed its multicolored splendor the same way she had watched the water droplets a few moments earlier. The Earthrise, the water, they were all one. They didn’t mean anything, they were just pretty.

Isadora was still laughing at the joke Kaylee had just told. She started stroking her friend’s hair and looking quietly back into the water. But Kaylee’s thoughts had flown upward, through that light, up to the surface of Earth.

They all knew the history of Earth, they all knew where they came from, and were scared by the teacher’s explanation of the oppressive gravity there. But there must be so much more to the place, Kaylee thought.

“We should go to Earth someday,” Kaylee said, more to elicit a reaction than out of any real conviction. Isadora knew this of course, and her olive-skinned face didn’t move a muscle as she took this in. Then she let a small smile play on her face for a moment before responding.

“All right. You go schedule a lander and explain the fuel costs to the launch manager. ‘I wanted to go down to Earth to show my friend that I can do crazy stuff. Yes, I know it’s as expensive to come back up from the surface as it is to go to Phobos, but she’ll be REALLY impressed!’ would it go something like that, maybe?”

Kaylee was in a strange mood. “They’d let me. The launch masters are all space-crazy anyway, and if they can come on a launch they’ll let you go anywhere. And anyway, we wouldn’t stay long.”

“We’d stay forever. Set one foot out of the lander and PLOP we’re both flat on our backs looking up at the sky for the rest of our lives. And don’t think the launch master would be much help, he’d be flat on his back inside the lander.”

“We’d build exo-suits, like the ones they use on the surface, but made to hold us up. And we could leave the tops off, because we can breathe that air.”

“Topless exo-suits? Kaylee you’re funny. What would you want to do down there anyway? Is this just because your parents want you to head out to Mars for a year?”

“No! I just wonder what it’s like. There’s hundreds of kinds of trees, and animals other than cats and dogs and chickens and alpacas.”

“What are those little things in the tree over there? Alpacas? No? Oh, that’s right. Wrens.”

“You know what I mean, Iz. We’ve got one hundred seven species of terran creatures here on Luna. Mars has seventy that have adapted so far. Someday they may have their own, or one of the deep ships might come back with something from far away, but I’m not holding my breath. There’s no life anywhere else in the universe, except for up there.”

Isadora looked up. It was a strange contradiction, she had to admit. The most beautiful place in the solar system was unreachable to both of the civilized planets, because the gravity would pin them down and wear their hearts out in a matter of months. Someone could possibly get acclimatized, but it would take years, maybe generations, and it wasn’t worth it. Trips that were sent down there stayed long enough to collect some water, or some new specimens that might help flesh out the ecologies on Luna or Mars, and Earth’s long-estranged children never felt so much as a breeze when they visited her. For some reason this made Isadora inexpressibly sad.

“Oh, Iz, I’m sorry, I didn’t mean to depress you,” Kaylee sat up and put an arm around her friend’s shoulders.

“It’s okay, Kay.” She laid her friend on Kaylee’s shoulder and sat quiet for a moment, watching the drops dancing up into the air sliding lazily back down into the pool.

“Maybe we should both go to Mars for a year. They’ve got that one open dome; well, kind of open. You know, the ion-shielded one, where you can go out into the low crevasses and there’s nothing over your head but sky. It’d be a lot like Earth.”

“Yeah, that’d be an experience. We could pretend we’re up there, on Earth. Maybe we could take a new species to Mars and help it integrate.”

Their talk turned to the unlikely animals that they would want on Mars, and eventually back to the pointless and happy friendly banter that they’d shared since they were little girls. They laughed their way to the Launch Master’s office, and two months later held hands as their shuttle left the shallow gravity well of Luna and began the long glide to Phobos Base. The Red Planet wasn’t the blue-green jewel of Earth, but it was starting to turn green, and it would do for now.

Isadora and Kaylee landed at Phobos station and were shown where to go to acclimatize themselves to the higher gravity once they went down to the surface, then were shown to their quarters while they were at Phobos. They asked to be able to stay in the same room, for moral support.

Turns out that wasn’t a problem; Phobos isn’t all that big, and one of the other rooms was being held for some explorer that was getting emergency-lifted out of the wilds.

The next lander wouldn’t be going down for another five days; so they had some time to explore and get spend time in the acclimatization booth. The booth was miserable; everything was heavy, slow, and it was hard to breathe. They were young and strong, though, and the doctors had no doubt that by the end of a month on the surface they’d be right at home. Lunar children often came to Mars on exchange. The Martians enjoyed the quiet, methodical Selenite children, and it was always enjoyable to watch them slowly find their strength, and resume the lyrical, graceful movements that defined their people.

As bad as the time in the acclimatization booth was, the rest of Phobos was delightful. It was built using the Martian style of construction: large, geodesic domes of clear material, so that the red planet was visible at all times. They were also able to watch all the launches and landings, though there weren’t many of these; just traffic between Phobos and Deimos bases. The launcher was fun to watch, though, as the shuttles were loaded onto the mag-rail track, positioned, charged, then flung out of Phobos’ gravity well to glide through the empty space to the other moon.

They met the incoming explorer, who greeted them only tersely, then oversaw the unloading of his cargo from the lander. The crews argued that it was going to go back down on the same lander, but he wouldn’t hear of leaving it in cargo.

He patiently explained to the girls what he had found, where and how had found it, and his plans to restore it, then build the equipment to receive and interpret it’s signals. It would be criminal, he said, to shut it back down, after all these years that it’s waited to send its messages and have someone interpret them.

Gabriel was a loner, by and large, but nobody could keep quiet with such an enthusiastic audience. The lunar girls were excited and in awe of the older man, his adventures. In time his reverence for the Spirit rover translated itself to them. By the end of the first day they were willing helpers, cleaning and polishing the rover carefully, listening with rapt attention to his explanations of how the Ancients had launched the lander to explore Mars, to help them find a place to live, and how this was his goal as well.

The Phobos crew watched, first with astonishment, then with fond amusement, as the two girls did something that nobody else had been able to do: Get Gabriel to actually open up to another person. He positively stewed during their acclimatization sessions, and he would just pace and wander until they emerged. The girls were only dimly aware of his behavior, and even if they did know that they were as admired as they were admiring they made no hint of returning his more personal feelings. Lunar/Martian pairings were not unheard of, but Explorer/Lunar pairings were. And maybe they wouldn’t ever happen. Still, bets were made for and against Gabriel being on the flight Luna one year from this time.

“Welcome to Mars, darlings! Stacie, get their bags, can’t you see their exhausted? Come, come, dears. The transport is just this way.” Mrs. Whitmore had taken in a number of Lunar exchange students, and was a professional now. Stacie Whitmore had seen a lot of very weak, very tired people take up the spare rooms in her home, but she too was a patient sort. She had found that Lunar girls usually made good friends after a while. Lunar boys, on the other hand, were so painfully shy around her that they never were much fun to talk to at all.

“Thank you, Mrs. Whitmore,” Isadora whispered. They’d been on the surface for less than an hour, and the pressure was so inescapable. Stacie saw how Isadora tried hard to keep Kaylee moving forward, even as she was herself nearly falling down, and easily lifted Isadora’s arm, then stood between the two Lunar girls and half-carried both of them to the transport.

“What’s so special about outside?” Stacie asked. They were sitting in the room the girls were sharing. Well, she was sitting, Kaylee was leaning hard against the wall, and Isadora was laying flat on her back. Stacie brushed her brown, straight hair back from her eyes and watched the two critically. She was working hard to keep them from feeling the claustrophobia that Selenites often started feeling about three days in.

“Well, we don’t have an outside we can visit easily in Luna,” Isadora said. “No chance of holding an atmosphere, not even with an ion shield.”

“And we’d like to see the sky.” Kaylee said heavily.

“Kay wanted to go to Earth, but if we’re having this much trouble here…” Isadora said and smiled a little. “I don’t think we would have survived even a few minutes on Earth.”

“Nonsense. You’ll both be up and around in a day or so. It’s just something you get used to.”

“Yeah, but something twice as heavy as this? I don’t know if I’d make it a couple of days down there.”

“Is it really so bad? I mean, I know it’s all what you’re used to, but I’ve never seen what the big problem is. I guess you don’t float around as easily here…”

“It’s like being covered in lead. Rocks. Lead rocks. And it’s downright dangerous, weighing this much.”

Stacie swallowed a laugh. The girls were slender, almost fragile looking things. She guessed she weighed about as much as both of them put together, and she was slender by Martian standards (which meant she was tiny by Earthling standards. The Lunar girls would have been seen as emaciated had they ever ventured to earth). Isadora caught her expression—that girl was far too good at reading people—and smiled forgivingly. “I can see why Lunar boys find you so interesting, Stacie. You’re happy, and down to earth…hah. That’s not really a phrase that any of us have any business using, is it?”

“But I look like a cow compared to you Loonies.”

“We like healthy-looking people in Luna. Tiny little things like us are practically invisible. You’d have a line of suitors as long as my arm five minutes after you walked through an airlock back home.”

Kaylee was asleep, pressed against the wall. With great effort Iz stood up, walked haltingly to Kaylee’s bed, and laid her down. She was sweating at the effort, and required Stacie’s help to get back to a chair.

“Mom’s going to kill both of us for letting her go to sleep before dinner.” Stacie said quietly. Iz just smiled. “Kay told me last night she doesn’t mind going down to dinner, but coming back up stairs afterwards to get ready for bed is murder. She’s considering going on a diet.”

“I guess that’s one way to turn invisible.”

Two weeks later Iz and Kay were much more acclimatized, and had even gained a bit of fame. The neighbors were used to the Whitmore family hosting Loonies and except for a few of the boys paid them no mind. However, when Gabriel the Explorer visited to see how they were settling in that got the neighborhood’s attention. When it came out that they had helped clean up Spirit after Gabriel’s famous crash they were suddenly the talk of the town. The socializing had helped them keep their minds off of the gravity, and had also gotten them to move around more than even Mrs. Whitmore could have done.

They were walking, even skipping from time to time, and Kay had started eating real meals again. Her diet threats had been somewhat worrying to Iz, but Mrs. Whitmore knew what she was doing. But today wasn’t just a good day, today was THE day. They were going outside. Mrs. Whitmore, Stacie, one of Stacie’s cousins (who just happened to be male and just happened to like skinny girls…) were all packing a picnic lunch (another novelty that the Selenite girls had never heard of before.) Isadora was walking quietly around the room, moving in slow bounds instead of steps. That seemed to be a Lunar habit that was hard to break.

Kaylee walked more “normally” but still seemed to take twice as many steps as were absolutely necessary. Of the two, Isadora seemed to be faster at understanding local customs, but she incorporated them into her own idioms. Kaylee, once she caught onto something, embraced it wholeheartedly.

The most visible example of this was skirts. They just simply weren’t worn on—Mrs. Whitmore corrected herself out of long habit—that is, in, Luna. But Martians liked them. Kaylee, once she realized that the majority of Martians wore skirts the majority of the time, purchased three and started wearing them constantly. A few days later Stacie and Mrs. Whitmore presented her with three more, which were slightly longer and had a few small weights in the hem for modesty’s sake. Selenite motion and Martian atmosphere meant that Kaylee’s skirts spent a lot of time billowing impressively around her.

The walk to the park wasn’t long, but the girls still tired quickly. They both insisted on carrying something, a thing that made Mrs. Whitmore happy. She had seen a few Loonies that refused to really do anything during their stay, and they went home much the same as they had come. These two would change, and would make both worlds better for it.

Kaylee was carrying the picnic blanket; a thick, heavy thing that could double as a tent in an emergency, not that either of the girls needed to know that. She switched shoulders frequently, a sure sign that it was a bit much for the slender redhead. But she never complained.

Isadora walked a step behind Kaylee, and Bran, Stacie’s cousin, walked to Kaylee’s left. Isadora’s face was clouded, but she still spoke pleasantly with Mrs. Whitmore and Stacie.

“We really wanted to see Earth, see the blue sky, the trees…oh, but Mars is beautiful. I’m glad we got to come here.” Stacie laughed a little bit, and was surprised to see Iz blush a little. “That didn’t come out so well, did it? I am sorry.”

“No, we understand Iz. Sometimes you don’t get what you want, but what you get is better than you could have imagined, is that it?” Isadora nodded and her blush faded a little. “Well, if you like the domes, wait until you see the park,” Stacie said and pressed the button to cycle the airlock.

“Hey, I thought the atmosphere outside was breathable! Why the airlock?” Kaylee asked.

“We haven’t taken it out yet. It’d be expensive, and what’s wrong with a safeguard?” Bran said. “Don’t worry, you’ll be fine out there.”

They shuffled into the airlock and the door behind them closed, the door in front of them opened and…

There was the sky. It wasn’t the blue sky of all those videos of earth. Instead it was the pale orange-red of Mars, with a faintly iridescent sheen from the ion shield.

But the color wasn’t the big thing. The big thing for the Lunar girls was that there wasn’t anything solid over their heads. The experience is best likened to a roller coaster: they were mostly sure they were safe, there were other people around, and the other people weren’t worried, so they shouldn’t be either. All the same, there was something wrong, some sense that if you didn’t follow the rules you could fall forever, straight up, straight into that sky. Instinctively their hands found one another as they stared straight up, barely breathing.