Terraforming Ganymede with Robert A. Heinlein

by Gregory Benford

Discovering Heinlein, for most who have, is like having sex or dropping acid: you don’t forget your first time.

Adrienne Martini, Locus 2011

There it is. Gosh, $2.50. But...I can’t wait!

I recall thinking that, when I sighted Farmer in the Sky for sale in the big Post Exchange in Tokyo. It was 1953 and less than 300 miles away, the Korean War was raging. Our father was a senior staff officer for General McArthur and often worked weekends and came home late at night. We had little time with him, and though our mother compensated, that’s not the same kind of fun.

So we read a lot. My brother Jim and I had already read Rocket Ship Galileo (published in 1947), Space Cadet (1948) and Red Planet (1949) from our school library. These early Heinlein books were the first science fiction we’d ever seen, since we grew up in deeply rural southern Alabama. SF opened horizons beyond those we already had discovered, living in occupied Japan.

We were fans, even if we didn’t even know it yet, so of course we couldn’t wait for the school to acquire Farmer. We pooled our money and bought the book, our first hardcover acquisition. It cost $2.50, a full five weeks’ worth of both our allowances, ran 216 pages and carried the great illustrations by Clifford Geary that made the Heinlein “juveniles” so visually memorable. A bargain, never regretted.

I still have it, though the dust jacket has vanished, lost somewhere in the many moves of a military family. Farmer and other Heinleins made such an impression on Jim and me that we took up astronomy, both of us got PhDs in physics, and I’ve published nearly a hundred astronomical scientific papers. I started my stargazing by focusing on Jupiter, the towering backdrop for Farmer in the Sky, which looked through my scope as in the figure. The thrill of personally seeing the Galilean moons, whose discovery by Galileo Galilei in 1610 shook mankind’s complacent geocentrism, was heady stuff to my teenage imagination.

My second novel was a direct homage to Farmer, a sort of prequel to its events, set many decades earlier. Published as a novella in Amazing in 1972, then expanded in 1976, The Jupiter Project tried to follow both the Heinlein model of scrupulous scientific clarity and (somewhat) his style.

Jupiter Project explores the social pressures on a small crew of scientists studying the Jovian system from a lab orbiting near Ganymede. Despite the potential for new discoveries, they face the stubbornly nagging question of whether space and exobiological research will ever have any relevance to the people back on Earth who fund such ventures. As the story begins, the station is about to be closed down, and the protagonist, seventeen year-old Matt Bohles, isn’t happy. Life onboard the aging cylinder space station is cramped, Spartan and dangerous, but "The Can" is home. To forestall being shipped back to a filthy, perilous and unfamiliar hell called Earth, he steals a small ship and sets out to discover Jovian life. Instead, he uncovers an even more important find. There the novel ends.

But that was just the plot setup. The real pleasure I had in writing The Jupiter Project lay in two learning curves. First, by copying Heinlein’s approaches, I learned much about writing. Dialog, character development, pacing, attention to authenticating detail in all the senses–Heinlein could imply an entire society, filled with taken-for-granted technological wonders far beyond his time, in a single throwaway sentence. (The classic example is “The door dilated.”) Next, I discovered a core truth of hard SF: dealing with reality, and then taking it a step further–in this case, imagining how to terraform Ganymede–is FUN. It’s playing tennis with the net firmly up.

In Farmer in the Sky young Bill Lerner and his family move to Ganymede. We first see a future Earth of austerity, dappled with some good foresight, such as an offhand description of what is clearly the casual use of microwave ovens:

I grabbed two Syntho-Steaks out of the freezer and slapped

them in quickthaw, added a big Idaho baked potato for Dad...

then stepped up the gain on the quickthaw so that the spuds

would be ready when the steaks were.

The journey is described with Heinlein’s characteristic blend of fast-paced adventure and meticulous research, a style of painless reader education that runs through all his books.

The novel describes the Lerner family’s flight to Jupiter, in which Bill organizes a Boy Scout troop to fill the time. Such activities recur throughout Heinlein YA novels -- he thriftily inserted scouting references so he could sell magazine rights to Boy’s Life, the magazine of the Boy Scouts of America. Heinlein strongly supported the Scouts, and once pointed out to me that everyone who had ever walked on the Moon was an Eagle Scout.

Farmer in the Sky celebrates 19th century American frontier life and homesteading by imagining much the same situations on Ganymede. But that demands terraforming, whereby sentient life from Earth transforms the very nature of nonsentient worlds. By this system, life from Earth–not just humans–grows independent of the fate of the Earth. Heinlein assumed, based on the best scientific knowledge of the times, that Ganymede has a rocky surface under an ice layer–which we now know it does, plus a deep ocean. By enormous amounts of work, ingenuity, and heartbreaking perseverance, these raw materials can be slowly reworked into a richly welcoming world.

Things go well at first, though conditions are harsh on Ganymede. Then a “rare” alignment of all four of Jupiter's major moons causes a catastrophic quake, killing most of the colonists. The family considers returning to Earth, but the pioneer spirit prevails. They remain, despite the dangers, to rebuild and win another home for humanity. Bill sets out to survey more of Ganymede, where terraforming continues, and by the end of the book we see how it’s changing.

Heinlein was scientifically accurate throughout, except for that quake. The devastating alignment of Jupiter's massive Galilean moons that he describes can never happen. The three inner moons–Io, Europa and Ganymede–orbit in resonance with one other, so that even if two line up, amplifying tidal forces, the third will always be non-aligned, frequently on the opposite side of Jupiter, offsetting the effect.

What else did he get wrong? Very little. He was scrupulously accurate, using the latest astronomical information. His only limit seems to be what was known at the time. He and his wife Virginia (biochemist, athlete and WWII WAVE, who was fluent in seven-plus languages and reputedly a better engineer than her husband) spent countless hours in research, fiercely dedicated to getting it right for their readers. They once spent days, back when slide rules were the apex of calculation speed, in working out the ballistics of an interplanetary trip (for The Rolling Stones), only to summarize their work in a few breezy paragraphs. Inspiring.

Heinlein knew, as did those who followed in his footsteps, that inevitably, as humanity opened the solar system to exploration and commerce, it would be cheaper in energy to tug in small asteroids from the orbits between Mars and Jupiter than to lift them with mighty rocket engines from Earth. So in the late '70s, I began thinking about world building and social implications of terraforming, constructing a future history that led to Farmer in the Sky and beyond.

I’ll present the first half of The Future of the Jovian System here as a popular historian would. The second installment will be prefaced with thoughts on recent astronomical discoveries about the Jovian system, and on how Robert Heinlein’s work still shapes the future, both in style and in his influence on others. I’ll take up what we now know of Ganymede and how future explorers might get from the early world-shaping of fiction to future environments there.

Father of all! in every age,

In every clime ador’d,

By saint, by savage, and by sage,

Jehovah, Jove, or Lord!



THEY SAID, OF COURSE, that it was impossible. They always do.

Even after the human race had moved into the near-Earth orbits, scattering their spindly factories and cylinder-cities and rock-hopping entrepreneurs, the human race was dominated by nay-saying stay-at-homes. Sure, they said, space worked. Slinging airtight homes into orbit at about one astronomical unit’s distance from the Sun was–in retrospect–an obvious step. After all, there was a convenient Moon nearby to provide mass and resources. But Earth, they said, was a benign neighborhood. You could resupply most outposts within a few days. Except for the occasional solar storm, when winds of high-energy particles lashed out, the radiation levels were low. There was plenty of sunshine to focus with mirrors, capture in great sheets of conversion wafers, and turn into bountiful, high-quality energy.

But Jupiter? Why go there? Scientific teams had already touched down on the big moons and dipped into the thick atmosphere. By counting craters and taking core samples, they deduced what they could about how the solar system evolved. After that brief era of quick-payoff visits, nobody had gone back. One big reason, everyone was quick to point out, was the death rate for those expeditions: half never saw Earth again, except as a distant blue-white dot.

Scientists don’t tame new worlds; pioneers do. And except for bands of religious or political refugee-fanatics, pioneers don’t do it for nothing. To understand why mankind undertook the most dangerous development project in its history (so far), you have to ask the eternal question: Who stood to get rich from it?

By the year 2124, humans had already begun to spread out of the near-Earth zone. The bait was the asteroids–big tumbling lodes of metal and rock, rich in heavy elements. These flying mountains could be steered slowly from their looping orbits and brought to near-Earth rendezvous with refineries. The delta V wasn’t all that large.

There, smelters melted them down and fed the factories steady streams of precious raw materials: manganese, platinum, cadmium, chromium, molybdenum, tellurium, vanadium, tungsten, and all the rare metals. Earth was running out of these, or else was unwilling to further pollute its biosphere to scratch the last fraction out of the crust. Processing metals is messy and dangerous. The space factories could throw their waste into the solar wind, letting the gentle push of protons blow it out to the stars.

Early in the space-manufacturing venture, people realized that it was cheaper in energy to tug small asteroids in from the orbits between Mars and Jupiter than to lift them with mighty rocket engines from Earth. Asteroid prospecting became the Gold Rush of the late twenty-first century. Corporations grubstaked loners who went out in pressurized tin cans, sniffing with their spectrometers at the myriad chunks. Most of them were duds, but a rich lode of vanadium, say, could make a haggard, antisocial rockrat into a wealthy man. Living in zero-gravity craft wasn’t particularly healthy, of course. You had to scramble if a solar storm blew in and crouch behind an asteroid for shelter. Most rock-hoppers disdained the heavy shielding that would ward off cosmic rays, figuring that their stay would be short and lucky, so the radiation damage wouldn’t be fatal. Many lost that bet. One thing they could not do without, though, was food and air. That proved to be the pivot-point that drove humanity still further out.

Life runs on the simplest chemicals. A closed artificial biosphere is basically a series of smoldering fires: hydrogen burns (that is, combines with oxygen) to give water; carbon burns into carbon dioxide, which plants eat; nitrogen combines in the soil so the plants can make proteins, enabling humans to be smart enough to arrange all this artificially.

The colonies that swam in near-Earth orbits had run into this problem early. They needed a steady flow of organic matter and liquids to keep their biospheres balanced. Supply from Earth was expensive. A better solution was to search out the few asteroids which had significant carbonaceous chondrites–rocks rich in light elements: hydrogen, oxygen, carbon, nitrogen. There were surprisingly few. Most were pushed painfully back to Earth orbit and gobbled up by the colonies. By the time the rock-hoppers needed light elements, the asteroid belt had been picked clean. Besides, bare rock is unforgiving stuff. Getting blood from a stone was possible in the energy-rich cylinder-cities. The loose, thinly-spread coalition of prospectors couldn’t pay the stiff bills needed for a big-style conversion plant.

From Ceres, the largest asteroid, Jupiter looms like a candy-striped beacon, far larger than Earth. The rockrats lived in the broad band between two and three astronomical units out from the Sun–they were used to a wan, diminished sunshine and had already been tutored in the awful cold. For them it was no great leap to Jove, hanging there 5.2 times farther from the Sun than Earth.

They went for the liquids. Three of the big moons–Europa, Ganymede, and Callisto–were immense iceballs. True, they circled endlessly the most massive planet of all, three hundred and eighteen times the mass of Earth. That put them deep down in a gravitational well. Still it was far cheaper to send a robot ship coasting out to Jupiter, looping into orbit around Ganymede, than it was to haul water from the oceans of Earth. The first stations set up on Ganymede were semiautomatic–meaning a few unlucky souls had to tend the machinery.

If they could survive at all. A man in a normal pressure suit could live about an hour on Ganymede. The unending sleet of high-energy protons would fry him, ripping through the delicate cells and spreading red destruction. This was a natural side effect of Jupiter’s hugeness – its compressed core of metallic hydrogen spins rapidly, generating powerful magnetic fields that are whipped around every ten hours. These fields are like a rubbery cage, snagging and trapping particles (mostly protons) spat out by the sun. Io, the innermost large moon, belches ions of sulfur and sodium into the magnetic traps, adding to the protons. All this rains down on the inner moons, spattering the ice.

It was not feasible to burrow under the ice to escape –the crew had to work outside, supervising robot ice-diggers. The first inhabitants of Ganymede instead used the newest technology to fend off the proton hail: superconducting suits. Discovery of a way to make superconducting threads made it possible to weave them into pressure suits. The currents running in the threads made a magnetic field outside the suit, where it brushed away incoming protons. Inside, by the laws of magnetostatics, there was no field at all to disturb instrumentation. Once started, the currents flowed forever, virtually without electrical resistance.

Those first men and women worked in an eerie dim sunlight. Over half of Ganymede’s mass was water ice, with liberal dollops of frozen carbon dioxide, ammonia and methane, and minor traces of other frozen-out gases. Its small rocky core was buried under a thousand-kilometer-deep ocean of water and slush. The surface was a thin seventy-kilometer-deep frozen crust, liberally sprinkled over billions of years by infalling meteors. These meteorites peppered the surface and eventually became a major facet of the landscape. On top of Ganymede’s weak ice crust, hills of metal and rock gave the only relief from a flat, barren plain.

This frigid moon had been tugged by Jupiter’s tides for so long that it was locked, like Luna, with one face always peering at the banded, ruddy planet. One complete day-night cycle was slightly more than an Earth-week long. Adjusting to this rhythm would have been difficult if the Sun had provided clear punctuation to the three-and-a-half-day nights. But even without an atmosphere, the Sun from Ganymede was a dim twenty-seventh as bright as at Earth’s orbit. Sometimes you hardly noticed it, compared to the light of Jove’s nearby moons.

Sunrise was legislated to begin at Saturday midnight. That made the week symmetric, and scientists love symmetry. Around late afternoon of Monday, Jupiter eclipsed the Sun, seeming to clasp the hard point of white light in a reddish glow, then swallowing it completely. Europa’s white, cracked crescent was then the major light in the sky for three and a half hours. Jupiter’s shrouded mass flickered with orange lightning strokes between the rolling somber clouds. Suddenly, a rosy halo washed around the rim of the oblate atmosphere as sunlight refracted through the transparent outer layers. In a moment the Sun’s fierce dot broke free and cast sharp shadows on the Ganymede ice.

By Wednesday noon it had set, bringing a night that was dominated by Jupiter’s steady glow as it hung unmoving in the sky. This slow rotation was still enough to churn Ganymede’s inner ocean, exerting a torque on the ice sheets above. A slow-motion kind of tectonics had operated for billions of years, rubbing slabs against each other, grooving and terracing terrain, erasing craters in some areas.

In the light gravity–one-seventh of Earth’s–carving out immense blocks of ice was easy. Boosting them into orbit with tug rockets was the most expensive part of the long journey. From there, electromagnetic-thruster robot ships lugged the ice to the asteroids, taking years to coast along their minimum-energy spirals.


“Ice might be nice, but wheat you can eat.”

So began one of the songs of that era, when the asteroids were filling up with prospectors, then miners, then traders. Then came settlers, who found the cylinder-cities too crowded, too restrictive, or simply too boring. They founded the Belt-Free State, with internal divisions along cultural and even family lines. (Susan McKenzie, the first Belt Chairwoman and a proud native of the Outermost Hebrides, was three generations removed from her nearest Earth-born Scot relative. Not that Belters stopped to think about Earth that much anymore.)

By then, the near-Earth orbital zone was as comfortable as a suburb, and as demanding. The few iceteroids available in the asteroid belt had already been used up, but ice from Ganymede, originally hauled to the asteroids, could be revectored and sent to the rich artificial colonies. As the colonies developed a taste for luxury, increasingly that meant food. No environment can be completely closed, so human settlements throughout the solar system steadily lost vapors and organic matter to the void. No inventory ever came up 100 percent complete. (Consider your own body, and try to keep track of a day’s output: feces, urine, exhaled gas, perspiration, flatus, sheddings. Draw the flow chart.) The relatively rich inner-solar-system colonies soon grew tired of skimpy menus and of the endless cycle in which goat and rabbit and chicken were the prized meats.

Inevitably, someone noticed that it would be cheap to grow crops on Ganymede. Water was plentiful, and mirrors could warm greenhouses, enhancing the wan sunlight. Since Ganymede was going to ship light elements to the asteroids and beyond anyway, why not send them in the form of grains or vegetables?

Thus began the Settlements. At first they were big, domed greenhouses, lush with moist vegetables or grain. The farmers lived below in the sheltering ice. Within two generations, humans had spread over a third of the moon’s purplish, grooved fields. In the face of constant radiation hazard, something in the human psyche said mate!–and the population expanded exponentially.

Robot freight haulers were getting cheaper and cheaper, since the introduction of auto-producers in the Belt. These were the first cumbersome self-reproducing machines, sniffing out lodes of iron and nickel, and working them into duplicates of themselves. An auto-producer would make two replicas of itself and then, following directives, manufacture a robot ion rocket. This took at least ten years, but it was free of costly human labor, and the auto-producers could work in lonely orbits, attached to bleak gray rocks where humans would never last. The ion rocket dutifully launched itself for Ganymede, to take up grain-hauling chores. Every year there were more of them to carry the cash crops sunward.

Working all day in a skinsuit is not comfortable. Day-to-day routines performed under ten meters of ice tend to pall. Fear of radiation and cold wears anyone down. For the first generation Ganymede was an adventure, for the next a challenge, and for the third, a grind. One of the first novels written in Jovian space opens with:

Maybe I should start off with a big, gaudy description. You know–Jupiter’s churning pinks and browns, the swirling white ammonia clouds like giant hurricanes, the spinning red spots. That kind of touristy stuff.

Except I don’t feel like writing that kind of flowery crap. I’m practical, not poetic. When you’re swinging around Jupiter, living meters away from lethal radiation, you stick to facts. You get so vectors and grease seals and hydraulic fittings are more important than pretty views or poetry or maybe even people.

The psychological profile of the entire colony took a steep downward slope. Even the kids in the ice warren streets knew something had to be done.

In the long run, no large colony could live healthily with the death-dealing threats to be found on any of the Jovian moons. Therefore, erase the dangers.

All sorts of remedies were suggested. One serious design was done for an immense ring of particles to orbit around Ganymede, cutting out most of the incoming high-energy protons. Someone suggested moving Ganymede itself outward, to escape the particle flux. (This wasn’t crazy, only premature. A century later it would be feasible, though still expensive.) The idea that finally won looked just as bizarre as the rest, but it had an ace up its sleeve.

The Ganymede Atmosphere Project started with a lone beetlelike machine crawling painfully around the equator of the world. Mechanical teeth ground up ice and sucked it inside, where an immense fusion reactor waited. The reactor burned the small fraction of heavy water in the ice and rudely rejected the rest as steam. From its tail jetted billowing clouds that in seconds condensed into an ammonia-rich creek.

This fusion plant crept forward on caterpillar treads, making a top speed of a hundred meters an hour. Its computer programs sought the surest footing over the black-rock outcroppings. It burned off toxic gases and left a mixture of water vapor, ammonia, oxygen, and nitrogen, with plenty of irritating trace gases. The greatest danger to it was melting itself down into a self-made lake. A bright orange balloon was tethered to the top. If the crawler drowned itself, the balloon would inflate and float the plant to the surface, to be fished out by a rescue team.

The trick was that the fusion-crawler wasn’t made with valuable human labor, but rather by other machines: the auto-producers. Decades before, the auto-producers had begun multiplying like the legendary rabbits who overran Australia. Now there were hundreds of them in the Belt, duplicating themselves and making robot freighters. The Belters were beginning to get irritated at the foraging machines; two had been blown to fragments for trespassing on Belters’ mines. Simple reprogramming stopped their ferocious reproduction and set them to making fusion-crawlers.

Freighters hauled the crawlers out to Ganymede, following safe, cheap, low-energy trajectories. The crawlers swarmed out from the equator, weaving through wrinkled valleys of tumbled stone and pink snowdrifts, throwing out gouts of gas and churning streams. The warm water carried heat into neighboring areas, melting them as well. A thin gas began to form over the tropics. At first it condensed out in the Ganymede night, but then it began to hold, to spread, to take a sure grip on the glinting icelands below.

The natives saw these stolid machines as a faint orange aura over the horizon. Crawlers stayed away from the Settlements, to avoid accidents and flooding. Their rising mists diffused the fusion torches’ light, so that a second sun often glowed beyond the hills, creeping northward, its soft halo contrasting with the blue-green shadows of the ice fields.


Copyright © 2011 by Gregory Benford

NASA image of Jupiter aurora in UV, Hubble Space Telescope Bright streaks and dots are caused by magnetic flux tubes connecting Jupiter to its largest moons: * Io: bright streak on the far left * Ganymede: bright dot below center * Europa: dot right of Ganymede dot Image originally from http://apod.gsfc.nasa.gov/apod/ap001219.html Credit: John T. Clarke (U. Michigan), ESA, NASA