done yet-not until we’re down on the new ground, turning the turf and planting our first crops. Now Venus is going to summarize what we’ve learned so far about the planet. And then we’ll decide, as a group, what we’re going to do about it.” That was Wilson, blunt and to the point. He nodded to Venus and backed off to stand with the gang of illegals and gatecrashers who had gravitated to his court.
Venus stepped forward, looking around at the expectant faces. She tapped her handheld. The crystal ball flared with light, and an image of Earth II coalesced.
It was a sphere more than a meter across, turning slowly around a horizontal axis. It was bright and detailed, and its glow, blue and gray, brown and white, lit up the faces of the watching people. Venus stayed silent, giving them a few seconds to take it in. The last murmurs hushed.
Holle remembered the first blurred images of the new planet, images taken from light-years out and constructed with extraordinary care by Venus’s planet-finder technologies. This new mapping was as detailed as any image of Earth as seen from space she had ever seen. And the planet wasn’t simply some abstract entity any more; now, after their months in orbit, it was a world already replete with human names. They had tentatively labeled the rotation pole that was currently pointing at the sun as “north”; the world turned counterclockwise as seen by an observer above that pole. Subject to months of unbroken heat from 82 Eridani the pole was blanketed in cloud, with storms visibly spinning off a massive central swirl.
At lower latitudes Holle made out landmasses that were already familiar to everybody aboard. A big strip of land stretching north to south across the equator was “the Belt,” a kind of elderly Norway with deep-cut fjords incising thousands of kilometers of coastline. The northern half of the Belt was currently ice-free, but its southern half, stretching into the realm of shadow, was icebound, and snow patches reached as far north as the equator. Sprawling across a good portion of the eastern hemisphere was the roughly circular continent they called “the Frisbee,” a mass of rust red broken by the intense blue of lakes and lined by eroded mountains. Its center was dominated by a huge structure, a mountain with a base hundreds of kilometers across, and a fractured caldera at the top. The mount was so like Olympus Mons on Mars that giving it the same name had been unavoidable, and it so dominated the overall profile of the continent, giving it an immense but shallow bulge, that the nickname “Frisbee” was a good fit. Then, to the west of the Belt, an archipelago sprawled, a widespread group of islands, some as large as Britain or New Zealand, that they called “the Scatter.” There was one more continent at the south pole, currently plunged in darkness and buried under hundreds of meters of winter snow, called “the Cap.” The world ocean itself had no name yet; the seas could be named when they were ready to go sailing on them, Holle thought.
The most exciting features were the patches of purple at the coasts of the continents and the shores of the lakes: life, native life on Earth II, plants of some kind, busily using 82 Eridani’s light to turn carbon dioxide into oxygen with their own unique photosynthetic chemistry.
Venus began without preamble.
“You all have access to the full reports in the ship’s archive. Today I’m just going to summarize the key findings.
“We’ve been here in this system for six months. We’ve surveyed atmosphere, land and oceans spectroscopically at all wavelengths, and have used radar to probe the subsurface and to map the seabeds, and have also dropped a series of penetrating probes for direct ground-truth sampling.” These were landers like slim missiles, hardened to withstand violent impacts and to bury themselves a few meters beneath the surface, with ground cameras that gave a close-up view of the final stages of the descent, and equipped with seismometers, chemical sensors, thermal sensors, magnetometers.
“Here’s the good news,” Venus said. “Obviously we have a world of about the right mass and the right volatile inventory, orbiting in a stable circular orbit at about the right distance from its sun to allow stable water oceans on the surface. ‘Right’ meaning it’s Earthlike.
“And on a basic level it’s habitable. If you landed in one of the shuttles and stepped outside, you’d experience a gravity of about eighty percent of a G; Earth II is less massive than Earth, and smaller in radius. Right now the northern summer is somewhere near its midpoint. If you were to stand at the pole you’d see the sun circle close to the zenith, right above your head. At the equator the sun is circling around the horizon, maybe dipping below for a few hours a day, depending on exactly where you are. It’s cold, there’s snow on the ground, but it’s no worse than a winter day in one of Earth’s temperate zones.
“Where the sun is up you could walk around with no more protection than a decent coat, some strong boots, a face mask. You could expose your skin, at least from the point of view of the sun’s radiation; there’s a healthy ozone layer. You would need some protection from cosmic radiation; the planet’s magnetic field is a lot weaker than Earth’s. You could breathe the air, we believe. It’s basically a nitrogen-oxygen mix of about the same proportions as Earth’s atmosphere. In the early days you’ll be wearing a face mask, in case of trace toxins from geological or maybe biological sources.
“We know there’s life down there. Life at the microbial level and, it seems, at some kind of simple multiple- cell level, something like stromatolites maybe. That’s what puts the oxygen in the air. It’s unlikely it will harm us, unlikely our alien biochemistries will interact significantly, but we’ll have to check it out. We believe that once we establish some terrestrial soil down there, Earthlike flora will take a hold: our crops will grow, our animals, when we incubate them, will be able to feed. Our children will be able to run and play.” She got a scattering of applause for that: But there was no joy in her face.
“This much we were able to guess from observations from Earth and Jupiter,” she said. “But all we could see from the solar system was a blurry dot with some evidence of mass, orbit, atmospheric composition. That’s all. On that basis it looked promising. But as it’s turned out, Earth II is not that close a sister to Earth I.
“This is a much less active world than Earth, geologically. You can see that from the eroded chains of mountains, the flat landscapes. The penetrators’ seismometers have detected few earthquakes. And we see no significant evidence of continental drift, no active plate-forming mid-ocean ridges, no subduction zones at plate boundaries-no colliding plates to trigger volcanism and to throw up mountain chains, as on Earth.
“Tectonic shift has seized up, here. It’s not absent, but is clearly operating at a much reduced rate than on Earth. And the result is the geology we see. The Frisbee is not unlike Australia, ancient and stable, so old its mountains are worn down, the rocks shattered to dust and rusted red. The big volcano at the heart of the Frisbee is a shield volcano, like Hawaii on Earth, and just like Olympus Mons on Mars-we named it well. It’s been created by a magma plume, an upwelling of hot material from the planet’s mantle, like a fountain. Olympus has been stuck over that plume for a long time-hundreds of millions of years, maybe. Over similar periods on Earth, the continents slide all the way from equator to pole.
“Is that important? We think so, for the sake of the long-term habit-ability of the planet. On Earth, plate tectonics play a key part in the vast geological and biological cycling that maintains Gaia. This world, with tectonic processes much reduced, can’t sustain such a significant cargo of life.
“Why has Earth II turned out to be so much less active than Earth? First, Earth II is that much smaller than Earth. Like Mars, it must have shed a greater proportion of its interior heat of formation, and a greater proportion of its inventory of radioactive materials will have decayed away. So the big internal heat engine that drives plate tectonics has run down. And second, we believe Earth II is actually an older world than Earth, by a billion years or more; whatever triggered planet-forming in this system happened much earlier than back home.”
Wilson put in, “So a billion years ago this world might have looked that much more like Earth.”
“Yes. With a much richer biosphere. I think we can expect to find traces of past complexity, lost as the planet has run down. That may be why we see no traces of extant intelligence.”
Kelly seized on that word. “ ‘Extant’? Does that imply you found traces of nonextant cultures?”
Holle felt unreasonably excited.
For answer, Venus tapped a handheld.
The turning world winked out of existence, to be replaced by an image of one of the larger islands of the Scatter, as if seen from a low-flying aircraft. Once it may have been mountainous; now its mountains were worn to stubs. “We call this Little Jamaica.” Venus pointed to features on a plain close to the sea. “Can you see?” There were faint circles, hints of straight-line features. “We don’t know what this is. You need to remember that this island is covered by the pack ice every local winter; any traces of surface structures, of buildings and cities, would long ago have been destroyed. It could be the trace of a quarry, we think. That might survive as long as a billion years. Maybe it’s something else, like a city. There are other indicators of intelligence. We’ve found no evidence of deep-buried carbon deposits. If there was any oil or coal on this world, or the local equivalent, it’s long gone. No
