Stephen Baxter - Ark

“Watch this sequence. Earth II’s day is longer than Earth’s, about thirty hours. These images were taken a couple of hours apart.”

It was like a crude, blurry animation, showing the world turning on a horizontal axis. That long central landmass moved downwards, and the other continent moved out of sight, under the belly of the world. The belt of shadow didn’t shift. The sun was out of sight, somewhere to her right…

Suddenly Holle saw it. “Oh. It’s a Uranus. The axis is tipped over, pointing at the sun.”

“Tipped through almost ninety degrees. Compared to, what, twenty-three and a half degrees for Earth? Actually we think it’s more like Mars, where the axis swings back and forth over periods of hundreds of thousands of years. Earth is stabilized by the moon; Mars lacks a big enough moon-and so does Earth II. The tipping seems to be tied into tidal effects from two big Jovians further out.”

“That’s why there’s no ice.”

“Yes. Each pole must be blasted by continual sunlight for half the year, while the other is in permanent shadow.”

“How could this come about?”

“Planets, and planetary systems, are common, Holle. We’ve learned that much-the sky is full of them. But the formation processes they go through are chaotic. They coalesce out of clouds of dust and ice, and then endure a hierarchy of impacts, from dust grains banging into each other up to the point where planet-sized masses collide. Not only that, there’s migration. Stars are born in crowded nurseries, and the remnant cloud is blown away pretty quickly by the light from neighboring baby stars. But before then tidal friction with the cloud can cause worlds the mass of Jupiter to go drifting inward through the system, scattering smaller worlds like birds. So there’s a lot of chance involved in the process. Anyhow this is probably why we have discovered so few ‘Earths;’ in nice stable circular orbits just the right distance from their star. And if you put constraints on the kind of star you want, you’re looking at an even smaller selection.”

Holle pulled her nose. “I have this feeling you’re drawing me into an argument.”

Venus sighed. “Well, it’s an argument that was dead before we left Jupiter. Holle, we’ve found Earths orbiting other kinds of star, not like Sol at all. M-class red dwarfs, for instance. If you orbit close in enough, you get reasonable temperatures. Some of those M-Earths are better candidates than Earth II — even based on what we knew at Jupiter. But there was a faction at Mission Control who wouldn’t countenance going anywhere but a yellow sun.”

“I remember,” Holle said. “I tried to keep out of it. Gordo Alonzo put his foot down in the end, didn’t he?”

“Yeah. ‘I’m not sending this crew to the fucking planet Krypton!’ Basically we took a bet that this candidate, from the restricted set we were prepared to consider, would pan out for us. Well, we lost. We’re doing some modeling of Earth II’s surface conditions. There are complex weather systems, quite unlike Earth. Evidently simple life survives there. But-”

“But it might not be a world for humans.”

“I don’t know. I hope it is. I fear not.” Venus sighed, and shut down her image sequence. “There’s a lesson here that just one astronomical parameter, in this case the axial tilt, may ruin a world from a human point of view. Which may be why we’ve seen no signs of intelligent life anywhere.”

Holle stared. “You’ve been looking?”

“Of course we have. Wouldn’t you? We’ve been looking the way we’re heading, and into the center of the Galaxy too, where most of the stars are. We’ve seen nothing, Holle, no signs of off-planet orbital infrastructures-no Dyson spheres, no ringworlds-and no sign that anybody’s meddled with the evolution of the stars. And not a bit of organized data in the radio hiss. It’s a big, empty Galaxy. Empty save for us. And that’s spooky.” Her voice was small, the pupils of her dark-adapted eyes huge in the soft light of her screen as she peered out at the stars.

Watching her, Holle wondered what kind of long-term effect the contemplation of a silent universe might be having on Venus and her people. The Ark sure didn’t need any more crazies. “Venus, I think we ought to start talking to people about this. Your doubts about Earth II. The sooner we start planning how we handle the issue the better.”

Venus grunted. “Sure. Start with Wilson, as he’ll be listening in anyhow. But keep it from the crew for now. No point stirring up negative reactions.”

“Thanks for the coffee. Umm, could you unlock the hatch?”

Holle put off going to see Wilson about Venus’s issues. She felt she needed time to think it through.

Instead, back in Seba, she went down to Deck Ten where she was due to meet Doc Wetherbee and Grace Gray for an update on the progress of Zane Glemp’s therapy. Wetherbee said Zane was participating in a dream circle there today, and Wetherbee wanted to observe.

Coming out of the airlock from the cupola Holle met Grace, and they crossed the deck heading for the downward stair. In the open area at the center of the deck Grace had to pull Holle back, to avoid the hard body of a kid who went plummeting down the length of the fireman’s pole.

“Whee!”

“Jeez,” Holle said, breathing hard. “Nearly got me that time.”

“Yes. They get faster every day. They dare each other to see how far they can fall without grabbing the pole.” They reached the ladders, and began their descent. “I persuaded Wilson to put a net across the hole in Deck Fourteen, to keep them from smashing into the hydroponics at least.”

“Little bastards go crazy.”

Grace, climbing down below Holle, grinned. “It’s hard to control them twenty-four seven, Holle. I mean, my Helen’s seven years old now.”

“I listen to them speak sometimes. Even their language is different from ours. They play complicated games of tag, and they must have fifty words for ‘gotcha.’”

“Yes. But no word for ‘sky’ or ‘sea’…”

They reached Deck Ten. More than a year after the fire the deck was still pretty much a ruin, with blackened walls and burned-out instrument racks. Even the flooring was a lash-up to replace the melted mesh panels. The whole of this hull had never really recovered, and had an air of shabbiness and age.

The dream circle was just getting started, and a toll collector was having the dreamers press their thumbs to a handheld pad to collect their payments. Wilson had installed a new currency of credits, collected electronically and stored in the ship’s memory; you were paid for your work, and in turn you had to pay for everything save for air and water. You even had to pay for sharing your own dreams on a burned-out deck. And a slice of every payment went straight to the common treasury, which Wilson controlled.

Among the dreamers was Zane, who looked shy, subdued. Holle wondered which alter was dominant today.

Grace was still talking about the children. “Kids just adapt to the place they’re brought up in, I guess. On Ark Three we used to deal with raft communities. Trading, you know. We encountered kids older than Helen who had spent their whole lives on the sea, who never saw dry land at all… They were happy, or could be. Wherever you’re born, you think is normal-all the world, all you ever need.”

“But they’re so different from us.”

“As we were different from our parents’ generation. They were bound to be. And I guess the next children, the colonists on Earth II, will be different again.”

“If we ever get there.”

“Sorry?”

“Oh, nothing. Hey, here’s Mike.”

Mike Wetherbee came clambering down from the upper decks. He looked harassed, as he always did; his hair graying, he looked to be aging quickly. He carried an emergency medical pack at his waist, and a small camera. He was here to film Zane’s participation in the dream circle. You never saw a camera nowadays save for such specific purposes.