There had been formulas for decades, first popularized in the RAND Corporation’s study Habitable Planets for Man. Every science-fiction writer and astrobiologist worth his or her salt had used them to determine the life zones—the distances from target stars at which planets with Earthlike surface temperatures might exist, a Goldilocks band, neither too hot nor too cold.
And the second of the four planets that could be seen around Tau Ceti was smack-dab in the middle of that star’s life zone. The planet was watched carefully for an entire year—one of its years, that is, a period of 193 Earth days. Two wonderful facts became apparent. First, the planet’s orbit was damn near circular—meaning it would likely have stable temperatures all the time; the gravitational influence of the fourth planet, a Jovian giant orbiting at a distance of half a billion kilometers from Tau Ceti, probably was responsible for that.
And, second, the planet varied in brightness substantially over the course of its twenty-nine-hour-and-seventeen-minute day. The reason was easy to deduce: most of one hemisphere was covered with land, which reflected back little of Tau Ceti’s yellow light, while the other hemisphere, with a much higher albedo, was likely covered by a vast ocean, no doubt, given the planet’s fortuitous orbital radius, of liquid water—an extraterrestrial Pacific.
Of course, at a distance of 11.9 light-years, it was quite possible that Tau Ceti had other planets, too small or too dark to be seen. And so referring to the Earthlike globe as Tau Ceti II would have been problematic; if an additional world or worlds were eventually found orbiting closer in, the system’s planetary numbering would end up as confusing as the scheme used to designate Saturn’s rings.
Clearly a name was called for, and Giancarlo DiMaio, the astronomer who had discovered the half-land, half-water world, gave it one: Soror, the Latin word for sister. And, indeed, Soror appeared, at least as far as could be told from Earth, to be a sister to humanity’s home world.
Soon we would know for sure just how perfect a sister it was. And speaking of sisters, well—okay, Ling Woo wasn’t my biological sister, but we’d worked together and trained together for four years before launch, and I’d come to think of her as a sister, despite the press constantly referring to us as the new Adam and Eve. Of course, we’d help to populate the new world, but not together; my wife, Helena, was one of the forty-eight others still frozen solid. Ling wasn’t involved yet with any of the other colonists, but, well, she was gorgeous and brilliant, and of the two dozen men in cryosleep, twenty-one were unattached.
Ling and I were co-captains of the Pioneer Spirit. Her cryocoffin was like mine, and unlike all the others: it was designed for repeated use. She and I could be revived multiple times during the voyage, to deal with emergencies. The rest of the crew, in coffins that had cost only $700,000 a piece instead of the six million each of ours was worth, could only be revived once, when our ship reached its final destination.
“You’re all set,” said the computer. “You can get up now.”
The thick glass cover over my coffin slid aside, and I used the padded handles to hoist myself out of its black porcelain frame. For most of the journey, the ship had been coasting in zero gravity, but now that it was decelerating, there was a gentle push downward. Still, it was nowhere near a full g, and I was grateful for that. It would be a day or two before I would be truly steady on my feet.
My module was shielded from the others by a partition, which I’d covered with photos of people I’d left behind: my parents, Helena’s parents, my real sister, her two sons. My clothes had waited patiently for me for twelve hundred years; I rather suspected they were now hopelessly out of style. But I got dressed—I’d been naked in the cryochamber, of course— and at last I stepped out from behind the partition, just in time to see Ling emerging from behind the wall that shielded her cryocoffin.
“ ’Morning,” I said, trying to sound blase.
Ling, wearing a blue and gray jumpsuit, smiled broadly. “Good morning.”
We moved into the center of the room, and hugged, friends delighted to have shared an adventure together. Then we immediately headed out toward the bridge, half-walking, half-floating, in the reduced gravity.
“How’d you sleep?” asked Ling.
It wasn’t a frivolous question. Prior to our mission, the longest anyone had spent in cryofreeze was five years, on a voyage to Saturn; the Pioneer Spirit was Earth’s first starship.
“Fine,” I said. “You?”
“Okay,” replied Ling. But then she stopped moving, and briefly touched my forearm. “Did you—did you dream?”
Brain activity slowed to a virtual halt in cryofreeze, but several members of the crew of Cronus—the Saturn mission—had claimed to have had brief dreams, lasting perhaps two or three subjective minutes, spread over five years. Over the span that the Pioneer Spirit had been traveling, there would have been time for many hours of dreaming.
I shook my head. “No. What about you?”
Ling nodded. “Yes. I dreamt about the Strait of Gibraltar. Ever been there?”
“No.”
“It’s Spain’s southernmost boundary, of course. You can see across the strait from Europe to northern Africa, and there were Neandertal settlements on the Spanish side.” Ling’s Ph.D. was in anthropology. “But they never made it across the strait. They could clearly see that there was more land—another continent!—only thirteen kilometers away. A strong swimmer can make it, and with any sort of raft or boat, it was eminently doable. But Neandertals never journeyed to the other side; as far as we can tell, they never even tried.”
“And you dreamt—?”
“I dreamt I was part of a Neandertal community there, a teenage girl, I guess. And I was trying to convince the others that we should go across the strait, go see the new land. But I couldn’t; they weren’t interested. There was plenty of food and shelter where we were. Finally, I headed out on my own, trying to swim it. The water was cold and the waves were high, and half the time I couldn’t get any air to breathe, but I swam and I swam, and then…”
“Yes?”
She shrugged a little. “And then I woke up.”
I smiled at her. “Well, this time we’re going to make it. We’re going to make it for sure.”
We came to the bridge door, which opened automatically to admit us, although it squeaked something fierce while doing so; its lubricants must have dried up over the last twelve centuries. The room was rectangular with a double row of angled consoles facing a large screen, which currently was off.
“Distance to Soror?” I asked into the air.
The computer’s voice replied. “1.2 million kilometers.”
I nodded. About three times the distance between Earth and its moon. “Screen on, view ahead.”
“Overrides are in place,” said the computer.
Ling smiled at me. “You’re jumping the gun, partner.”
I was embarrassed. The Pioneer Spirit was decelerating toward Soror; the ship’s fusion exhaust was facing in the direction of travel. The optical scanners would be burned out by the glare if their shutters were opened. “Computer, turn off the fusion motors.”
“Powering down,” said the artificial voice.
“Visual as soon as you’re able,” I said.
The gravity bled away as the ship’s engines stopped firing. Ling held on to one of the handles attached to the top of the console nearest her; I was still a little groggy from the suspended animation, and just floated freely in the room. After about two minutes, the screen came on. Tau Ceti was in the exact center, a baseball-sized yellow disk. And the four planets were clearly visible, ranging from pea-sized to as big as grape.