The issues and ideas of planetary engineering will be examined from a number of points of view. First, of course, is an investigation of the term, Earth-like planets. To understand that goal, we will have to see how Earth itself was formed and how it evolved, and what random factors combined to create "by accident" the kind of world we propose to create "on purpose." The definition of an Earth-like planet also requires an understanding of the factors which together form a biosphere, a planet- wide ecology which supports life as we know it on Earth. Since we are going to have to manufacture an extremely intricate pattern, we need an appreciation of the often subtle ecological chains of cause-and-effect which drive our own home planet's biosphere.

Beyond Earth lie numerous planets, moons, asteroids, comets, and other miscellaneous flotsam and jetsam of the Solar System, bathed in solar energy and containing vast amounts of different kinds of fuels. We will need to inventory these objects and energy sources and classify them by their composition, location, and utility. Next, we will need to examine some of the possible tools and techniques by which the Solar System can be rebuilt; this, in place of the random "hand waving" often resorted to by visionary space prophets. The arsenal of human ingenuity contains far more powerful "tricks of the terraforming trade" than might initially be supposed: rockets, solar sails, thermonuclear bombs and other gad- gets, biological and genetic tools, and of course, people themselves.

Mars is the most likely target for colonization, and it has been the topic of numerous recent unpublished studies of great potential signifi- cance. So we will consider that planet first, examining its problems and potentials in two full chapters. Venus, the next planet considered for terraforming, has its own special problems, including many not faced by spokesmen who carelessly conjure up visions of air-cleaning algae and similar simple solutions. Besides Mars and Venus are smaller bodies such as the Moon, Mercury, Ganymede, Titan, and others, which are potential sites for constructing new Earths.

Finally, we shall examine the possible motivations, objections, and philosophical issues of rebuilding the Solar System. Those questions also depend heavily on speculations and suppositions which have gone be- fore, so now let us begin by turning to the history of the concept of planetary engineering.

The First Visionaries
The first references to planetary engineering dealt mainly with schemes for altering the spin rate or axis of Earth itself, or with changing the courses of asteroids and comets. These themes were far more wide- spread than may be realized.

Milton's Paradise Lost contains a reference to angels tilting the axis of Earth from straight north-south (which accounted for the mild climate of Eden) to the present 230, creating alternating seasons. Jules Verne had the same idea only in reverse: his Baltimore Gun Club engineers, having just sent men around the moon, turned to untilting Earth by means of a giant cannon set up on the equator (in order to ameliorate the polar climates so as to allow mining operations). The Russian space genius Konstantin Tsiolkovskiy touched on various topics relevant to terraforming in his works at the end of the nineteenth century, and although his books were not published in time to have any contribution to the work of Western space pioneers, they nevertheless exerted a profound influence on Russian space theorists.

The first alien world to have its climate altered was Mars, at least in the imagination of Percival Lowell. This wealthy Boston astronomer became fascinated with the canals of Mars, and in three books published between 1895 and 1908 he expounded his main thesis: Mars was a dying world, but its inhabitants were engaged in massive planetary engineering to stave off ecological disaster. This fantastic image became the stage for the Barsoom novels of Edgar Rice Burroughs, which first appeared in

1912. On Barsoom, giant machinery was used to maintain the atmosphere in a breathable condition. All Burroughs would have had to have imag- ined was this planetary engineering being conducted by people from Earth, and he would have invented the modern concept of terraforming.

One of the first widespread uses of the ideas of planetary engineering in fiction was in Olaf Stapledon's ambitious "future history" of the human race, Last and First Men. The author used concepts of the alteration of Earth's climate, of a war between Mars and Earth over water, and of an accidental alteration of the Moon's orbit. But perhaps his most evocative contribution was in his description of the moral issues involved with the need for a future race of men to leave a dying Earth and settle a new planet. "Clearly humanity must leave its native planet," Stapledon sets forth as the problem. "The only alternatives were Mars and Venus. The former was . . . Without water and without an atmosphere. The latter had a dense moist atmosphere; but one which lacked oxygen. . . . It was necessary either to remake man's nature to suit another planet, or to modify conditions upon another planet to suit man's nature."

Venus was chosen since "Mars could not be made habitable without first being stocked with air and water; and such an undertaking seemed impossible." At first, appropriate vegetation was introduced on Venus (which was covered with a great ocean) to break down the atmosphere and release oxygen; when this proved too slow, electrolysis stations were set up, using some unspecified power source to break down the water into oxygen and hydrogen and the hydrogen was expelled from the planet by "an ingenious method" not described otherwise.

But a problem arose. Deep in the Venerian oceans, a previously undiscovered intelligent civilization "resented the steady depletion of their aqueous world, and were determined to stop it. . . . And as all efforts to parley with the Venerians failed completely, it was impossible to effect a compromise.

"What right had man to interfere in a world already possessed by beings who were obviously intelligent?" Stapledon asked. "On the oth- er hand, either the migration to Venus must go forward, or humanity must be destroyed. . ." Additionally, it turned out that the Venerian civili- zation itself was doomed through climatic changes wrought by natural forces on their own world. "Man would merely hasten their destruction," Stapledon rationalized.

It was therefore determined to put them out of their misery [caused by man's terraforming changes] as quickly as possible. . . . This vast slaughter influenced the mind of the fifth human species in two opposite directions, now flinging it into despair, now rousing it to grave elation. For on the one hand the horror of the slaughter produced a haunting guiltiness in all men's minds, an unreasoning disgust with humanity for having been driven to murder in order to save itself. . . . On the other hand a very different mood sometimes sprang from the same sources. . . . As for the murder of Venerian life, it was, indeed, terrible, but right. It had been committed without hate . . . . This mood, of inexorable yet not ruthless will, intensified the spiritual sensibility of the species. .

[The project was carried out, but success was less than had been hoped for.] The climate was almost unendurable. The extreme difference of temperature between the protracted day and night produced incredible storms, rain like a thousand contiguous water- falls, terrifying electrical disturbances, and fogs in which a man could not see his own feet. . . . [A disease appeared which was] finally traced to something in the Venerian water, and was supposed to be due to certain molecular groupings. . . . These troubles were aggra- vated by the devastating heat. . . .

Over millennia, Stapledon recounted the adaptations to the new homeworld. (Earth, as expected, was destroyed.) Millions of years later, the need arose to move closer to the Sun, so an atmosphere was provided for Mercury. But new factors frustrated that project, and the remnants of the human race migrated to a terraformed Neptune, made habitable by increased solar activity. Almost two billion years in the future, Stapledon conceived of an age when "they gained control of the movement of their planet. . . . They were able, with the unlimited energy at their disposal, to direct it into a wider orbit, so that its average climate became more temperate, and snow occasionally covered the polar regions. But as the ages advanced, and the sun became steadily less ferocious, it became necessary to reverse this process and shift the planet gradually nearer to the sun."

Stapledon's galaxy-spanning prophecies stunned his readers in the 1930's. Even so, they were probably willing to conceive of such occur- rences millions or billions of years in the future, but concluded that they had no relevance for the coming decades or even centuries. It remained for subsequent writers to reduce the scope of such visions and bring them within range of our own civilization. Planetary engineering was to be- come a possibility for our immediate descendants.

The word terraforming itself, which Robert Heinlein called "a charm- ing neologism, euphonic and self-defining," was coined by Jack Williamson in a series of stories published (under the pseudonym Will Stewart) in the 1940's and republished as the twin novels "Seetee Ship" (1951) and "Seetee Shock" (1949). Williamson described "spatial en- gineers" who used "paragravity generators" to terraform the Moon, Mars, Venus, the satellites of Jupiter, and, finally, many asteroids. This was done in the name of human destiny: "The spatial engineers had triumphed over the cold black eternal enmity of space to claim . . . Bold new outposts for mankind . . . [and] to cloak in green life all the riven stone of a world born dead."

The first science fiction novel completely based on the concept of terraforming was Robert Heinlein's Farmer in the Sky (1950). Three dec- ades after first publication, the tale of the tribulations and triumphs of settlers on a rebuilt Ganymede, one of the giant moons of Jupiter, remains a classic and is in its fifth printing. Newly discovered scientific and cli- matological facts have demolished the story's scientific basis, but will never alter its drama and its highly readable presentation of the foun- dations of planetary engineering. (It introduced the word ecology more than a decade before the environmentalist movement began to flourish.)

Heinlein's Ganymede was home for several thousand colonists ben- efiting from a fifty-year-long project which had used nuclear power to melt the ice and ammonia of the original surface and to break down the water into oxygen (which provided the breathing air) and hydrogen (which rose to the top of the atmosphere and hence was "not dangerous"). An unspecified technology maintained a "heat trap" which enhanced an artificial "greenhouse effect," keeping the sunlight in and causing Ganymede to look "like the inside of a sack" from space. But "it's not dark on the ground," Heinlein's narrator realized, since the light got in but just couldn't get out, ". . And a good thing, too."

Some obvious and some subtle problems involving terraforming were described in Farmer in the Sky (although Heinlein did not seem to realize, for example, that a pure oxygen atmosphere would lead to every piece of organic material on the planet, skin and bones included, bursting into searing flames as soon as the first spark occurred). The crucial nitrogen cycle involved in the biological production of protein was mentioned. The isostatic dangers caused by melting lots of ice and redistributing large amounts of liquid water were involved in the dramatic highlight of the book: an earthquake destroys the "heat trap" which leads to a sudden freezeup which nearly wipes out the colony. The biology is tailor-made: "almost everything grown on Ganymede was a special mutation adapted to Ganymede conditions." Seasonal climate, too, was designed by turn- ing winter "on" and "off" via modulating the "heat trap": "we had to have winter; the freezing and thawing was necessary to develop the ground."

Problems involved with setting up a planetary ecology were not underestimated, as Heinlein's young narrator explained: "The trouble with ecology is that you never know where to start because everything affects everything else. . . . Take the old history book case: the English colonies took England's young bachelors and that meant old maids at home and old maids keep cats and the cats catch field mice and the field mice destroy the bumble bee nests and bumble bees are necessary to clover and cattle eat clover and cattle furnish the roast beef of old England to feed the soldiers to protect the colonies that the bachelors emigrated to, which caused the old maids." This particular chain may be dubious; the concern for such ecological subtleties rests on far firmer foundations.

Social issues also appeared as Heinlein's teenage hero argued with a friend on Earth who was trying to dissuade him from emigrating. The friend said, "My old man says that nobody but an utter idiot would even think of going out to Ganymede. He says the Earth is the only planet in the system fit to live on and that if the government wasn't loaded up with a bunch of starry-eyed dreamers we would quit pouring money down a rat hole trying to turn a bunch of bare rocks in the sky into green pastures. He says the whole enterprise is doomed. It's a perilous toehold, artificially maintained and someday the gadgets will bust and the whole colony will be wiped out and then we will quit trying to go against nature."

Of course, Heinlein felt just the opposite, as his character described his own concept of human destiny: "They say man is endlessly adaptable. I say on the contrary that man doesn't adapt himself as much as he adapts his environment." His concept of the essence of humanity allowed him to judge as "human" a vanished alien race because "they weren't ani- mals, pushed around and forced to accept what nature handed them; they took nature and bent it to their will."

The cost of the project brought up an issue which Heinlein could not duck, so he used a very clever way out. Although the public reason for the Ganymede project did involve an attempt to make it financially profitable and to use it for shipping excess population, the 'real reason' in Heinlein's world view was to establish an independent human civi- lization off Earth, safe from the inevitable nuclear holocaust which pop- ulation and resource-exhaustion problems would bring to Earth. Enlight- ened members of the world government were motivated in their support of the expensive Ganymede project by such logic, Heinlein suggested.

Heinlein, more than any other writer, had humanized terraforming. Through his novel he had shown the hopes, fears, doubts, and motivations of realistic people involved in a terraforming project. The change in scale from Stapledon's eons and galaxies to Heinlein's first person narrative coincides with a change in attitude toward planetary engineering. Once it was sheer fantasy for the unimaginable future; now it was conceivable for tomorrow or the day after.

Science fiction continued to return to the theme of terraforming. As summarized in The Visual Encyclopedia of Science Fiction (1977), Ganymede was still the favorite of many writers. In "The Snows of Ganymede" (1955), PouI Anderson described the terraforming of Gany- mede, a popular idea used earlier by Heinlein and more recently in Greg Benford's Jupiter Project (1972). Terraforming was the theme of George 0. Smith's "Speculation" (1976), which told how organic Earth soil was transported to Mars and cultivated. Earth plants then gradually spread across the planet, the microorganisms in the Earth soil penetrating the Martian surface, paving the way for terrestrial vegetation. The same au- thor's "The Planet Mender" (1952) described cosmic engineering where mountains of ice from Uranus were routed via Mercury and Phobos to become rain on Mars. Heinlein also wrote of cosmic engineering in his book, Between Planets (1951). He mentioned a plan to move Pluto and Neptune nearer the Sun, while pushing Mercury farther out. Still another terraforming work, Frank Herbert's Dune (1965) depicted a desert planet being reclaimed by its inhabitants.

Scientists Take Notice
References to terraforming were not being made just by science fiction writers. The brilliant galaxy specialist, Dr. Fritz Zwicky of the California Institute of Technology, came out with such forecasts even before Heinlein's Farmer in the Sky was published.

Delivering the annual "Halley Lecture" at Oxford on May 12, 1948, Dr. Zwicky (then fifty years old) remarked that "the application of . . . Knowledge to active interference in material celestial affairs and the re- construction of sections of the universe other than the surface of the Earth has not yet been realized. It remains a distinct possibility for the future . . ." At the close of his paper ("Morphological Astronomy," printed in the August 1948 issue of "Observatory"), Zwicky went into greater detail, suggesting that "in the wake of the realization of large-scale nuclear fusion there will, no doubt, follow plans for making the planetary bodies habitable by changing them intrinsically and by changing their position relative to the sun. These thoughts are today perhaps nearer to scientific analysis and mastery than were Jules Verne's dreams in his time."

Zwicky returned to this theme in later writings. With the dawn of the space age, he considered possible operations on the Moon, while keeping his eyes on more distant horizons. In 1960, he wrote that "mod- ern astronomy intends to embrace two additional activities: the direct experimentation with extraterrestrial bodies and phenomena, and the possible reconstruction of celestial bodies, starting with those of the Solar System. . . . A more complete survey of this future field of endeavor is badly needed." After presenting ideas for the creation of an atmosphere for the Moon, he continued: "For Mars and Venus which are large enough to retain an atmosphere it would thus be a question of altering this at- mosphere sufficiently through generation of oxygen and elimination of certain other gases to make them inhabitable. Mars in this respect would seem to be the brightest prospect." Zwicky anticipated that "the chance of exploring entirely new worlds, pioneering in making them habitable, and creating new forms of society, will be the greatest challenge for all great minds." Before he died in 1974, Zwicky had tried to accept that challenge and interest others in it, but without measurable success.

The Venus Algae and Carl Sagan
On the occasion of the launching of the first space probe towards Venus in February 1961 (it failed), a twenty-six-year-old research fellow at the "Space Sciences Laboratory" of the Institute for Basic Research in Science in Berkeley, California, wrote a summary of what was known, suspected, and projected for the planet Venus for the "Current Problems in Research" column of "Science" magazine. The young scientist's name was Carl Sagan.

"It appears very unlikely that there are indigenous surface organisms at the present time," Sagan wrote, since scientists were beginning to suspect that Venus was the hell-hole it actually is. "If, indeed, Venus proves to be without life, there will exist the prospect of microbiological planetary engineering."

Such a speculative topic had rarely been mentioned before, and it was tagged onto the end of the otherwise very sober summary of current knowledge and ignorance about the planet. But there was no attempt to downplay the significance of Sagan's proposal, taken from the pages of science fiction and now proclaimed on the pages of "Science" magazine.

"To prepare Venus for comfortable human habitation, it is necessary to lower the surface temperature and to increase the partial pressure of molecular oxygen. Both ends could be accomplished if a means were found to dissociate carbon dioxide to oxygen and elemental carbon . . . . Extensive laboratory experiments should be performed on the ecology of the algae in simulated Cytherian [Venusian] environments . . . The microbial re-engineering of Venus will become possible . . . The green- house effect is rendered less efficient and the surface temperature falls . . . Surface photosynthesis becomes possible . . . Rain will reach the surface . . . Venus will have become a much less forbidding environment than it appears at present . . ."

It really doesn't matter that Sagan was quite wrong about what might happen, and far off base on his concept of the conditions on Venus. He had estimated temperatures still too temperate, and surface pressure still too low by a factor of thirty. He believed that "the quantities of water vapor in the two atmospheres are approximately equal," when Venus is actually highly depleted in water in comparison to Earth.

As new data came in, the "algae solution" for rebuilding Venus was appropriately modified. More important than the factual problems, how- ever (and Sagan was as well informed as anyone else at that time), was the public's exposure to the concept of planetary engineering on Venus, and the respectability which the idea garnered from having been men- tioned on the pages of "Science". Terraforming still had a long way to go to acceptability-but it had started along the road.

Taking Planets Apart
Terraforming received additional scientific respectability from Dr. Freeman Dyson of the Institute for Advanced Study in Princeton, who described various types of planetary engineering possibilities in light of their interstellar detectability. That is, perhaps we would detect extrater- restrial civilizations, not from their deliberate radio transmissions, but from noticing the physical results of their planetary and stellar engineering activities.

Speaking in California in April, 1965, Dyson described his approach to what is "possible" for planetary engineering: "My rule is, there is nothing so big nor so crazy that one out of a million technological societies may not feel itself driven to do, provided it is physically possible . . . I assume that all engineering projects are carried out with technology which the human species of the year 1965 A. D. can understand. This assumption is totally unrealistic. I make it because I cannot sensibly discuss any technology which the human species does not yet understand . . . My third rule is to ignore questions of economic cost." On these grounds, what kinds of planetary engineering are possibly waiting out there on the galaxy to be discovered?

"It is possible to take planets apart," Dyson claimed. "One can think of several feasible methods of disassembling a planet." One method, which Dyson describes using Earth as an example (while disclaiming any advocacy of actually doing it to Earth), involves using electromagnetic force to transfer the momentum of orbiting satellites into Earth's rotation, and accelerating the planet to the point where centrifugal force could tear it apart. Calculations show that if all of the solar energy passing through a region three-quarters of a million kilometers across (about equal to the circle bounded by the Moon's orbit) were applied at 100% effi- ciency to speeding up the spin of Earth, the disintegration point (when the "day" was reduced to less than 100 minutes) would come in about 40,000 years. Dyson had proved his point.

Since at least some technological civilizations would expand out into the galaxy and would engage in massive stellar engineering, Dyson asks why we have not detected signs of such activity. "We must ask: what does a galaxy look like when technology has taken over? . . . A galaxy in the wild state has too little matter in the form of planets, too much in the form of stars. . . . A "tame" galaxy, then, would be different: there would be enhanced infrared radiation, the "waste heat" of futuristic industries; there would be a large ratio of nonluminous to stellar mass; there would be a lot of star-star collisions or artificially induced super- novas, since these are two potential techniques for taking stars apart; there would be "an unusual abundance of short-lived giant stars and deficiency of ordinary dwarf stars," because of the former's utility for supporting habitable solar systems over the "short run" of several hundred million years.

As an example of the contributions such theorizing about terraform- ing can have for other, seemingly unrelated intellectual pursuits, Dyson then proceeded to tie his galactic engineering speculation into the context of the search for extraterrestrial intelligence (or "SET!"). "Why do we not see in our galaxy any evidence of large-scale technology at work? . . I have the feeling that if an expanding technology had ever really got loose in our galaxy, the effects of it would be glaringly obvious. Starlight instead of wastefully shining all over the galaxy would be carefully dammed and regulated. Stars instead of moving at random would be grouped and organized . . . So in the end I am very skeptical about the existence of any extraterrestrial technology."

"Dyson Sphere" is the term given to one such planetary engineering project described by the Princeton scientist in the early 1960's. Once a large planet had been taken apart (Dyson computes that Jupiter's total vaporization would require "only" the Sun's total energy output for 800 years), the material could be used to construct a sphere around the entire Sun at a distance equal to the radius of Earth's orbit. In some versions, this sphere is solid; in others, it consists of an intricate ballet of separately orbiting small objects. Whatever form it might take, it would nearly fully utilize the entire energy output of the Sun.

NASA Recognizes Terraforming
Terraforming finally received an official blessing from NASA when, in 1975, it was the topic of a special study concentrating on Mars. A team of scientists at the NASA Ames Research Center near San Francisco examined the possibilities of introducing Earth life on Mars, or, if Mars was not habitable in its present situation, of altering the conditions of the planet. Their study was published by NASA in 1976 and was entitled "On the Habitability of Mars: An Approach to Planetary Ecosynthesis." Several members of the study group, along with unofficial consultants, again met in November 1976 at the 13th Annual Meeting of the Society of Engi- neering Science at NASA's Langley Research Center near Norfolk, Vir- ginia. They put together a special session at the conference, but were unable to call it "Planetary Engineering" as planned; it came out "Plan- etary Modeling" instead. The titles of the presented papers, however, gave clear indication of what was being discussed: "The Making of an Atmosphere," "Atmospheric Engineering of Mars," and "Creation of an Artificial Atmosphere on the Moon."

The Public Notices Terraforming
In 1978-1979 there appeared in popular scientific magazines a series of articles on the topic of planetary engineering. First off the presses, in the May 1978 issue of "Astronomy", was an article by this writer entitled, simply, "Terraforming." Public reaction was good, so the article was re- written by the staff of "Astronomy" for their children's astronomy offshot magazine, "Odyssey", appearing in the January 1979 issue under the title "Man on Mars-it Might be You!" The July, 1978 issue of "Analog Science Fiction/Science Fact" carried an article by Ralph Hamil entitled "Terra- forming the Earth," which did not mention other planets, but did cata- logue a myriad of planet-wide engineering projects which could transform the face of our own planet. Meanwhile, NASA futurist Dr. Jesco von Puttkamer, a regular contributor to "Future" magazine (later, "Future Life"), wrote "In Earth's Image: The Terraforming of Other Planets" for the March 1979 issue. Coming out at practically the same time was an entirely new version of this writer's speculations, published by the new "OMNI" mag- azine as "Farming the Planets".

The First Terraforming Colloquium
By late 1978 it appeared time to prepare for one more step on the road from science fiction to science speculation. Anticipating the new data which would soon come in from Venus and Jupiter, as well as the continued publication of Viking data analysis, I made inquiries about the suitability of holding a speculative special session on terraforming at the imminent annual Lunar and Planetary Science Conference, to be held in Houston in March 1979. Encouraged by volunteer participants and by the conference staff, a public "call for papers" was announced at the American Astronautical Society conference in Houston on October 30. Over the months that followed, a wide selection of previously uncoor- dinated research came to my attention. One disappointment was the decision by the conference management to allow the terraforming session to use conference facilities, but not to give the session any official status. According to the letter announcing this decision, terraforming was "highly speculative and not closely linked to exploration of the planets, the theme of this conference." It was not an unreasonable judgment, and the session planning went forward.

The evening of March 16, 1979 marked the world's first conclave of terraforming researchers, who had traveled from California, Colorado, and Washington, D.C., to be with fellow enthusiasts from Texas. Prior to the colloquium, the participants met at a picnic supper on the lawn of the Lunar and Planetary Institute, a handsome building on the shore of Clear Lake which had formerly been a millionaire's summer retreat. The picnic's idyllic setting was marred by attacks of fire ants, underscoring the small scale problems of setting up a planet-wide ecology hospitable to human life-somewhere else, if not on Earth!

The colloquium itself lasted four hours and drew over one hundred planetary scientists from the Tenth Annual Lunar Science Conference, then in progress. The contents of the papers discussed that evening have been incorporated into this book. Beyond the technical topics was another aspect of the concept which moved one nationally renowned space sci- entist to proclaim, "I'm most impressed by the enthusiasm of these young people and their willingness to do their homework and face real prob- lems." For much of the scientific community, the colloquium served as a public announcement that yet another "crackpot idea" was about to move closer to scientific respectability at last.

The time was ripe. Decades, even centuries of writers had popular- ized and prophesied. Independent theorists had gone their own ways in isolation. Now the separate threads could reinforce each other and be woven into a tapestry of stunning perspective which this book attempts to portray.

Chapter 1: Terraforming Manifesto
The first human beings to visit another world beyond this Earth sensed immediately the incompleteness of its Creation. When the Apollo 8 crew- men saw the Moon close up, they seemed to realize that, although Earth had undergone a full evolution from dust to human home-world, the evolution of the Moon was unfinished. It remained sterile and lifeless, an affront to the astronauts' sensibilities.

Consciously, perhaps, they did not anticipate the possibility that future generations of spacefarers would be able to take up where nature had left off, and would be able to remake the desolate Moon into a smaller copy of Earth, complete with its own oceans, forests, prairies, and cloud-studded blue skies. Few people anywhere on Earth, even now, appreciate that remote possibility.

Yet that possibility, and the stark contrast between the oasis Earth and the stillborn world of the Moon, might have been the basis of the insight that moved those astronauts to their unlikely choice of the Biblical reading that they radioed back to Earth. It was Christmas Eve, 1968, but the far-ranging spacemen did not choose to read from any Gospel account of Christ's nativity. They went, instead, to the creation of Earth-and foreshadowed the nativity of a whole new world.

"In the beginning, God created the Heaven and the Earth," intoned William Anders across 400,000 kilometers of space. "And the Earth was without form, and void." Below him, an empty, half-formed world passed by his porthole.

Following the turn of Apollo 8's navigator James Lovell, spaceship commander Frank Borman finished the reading: ". . . And God said, let the waters under the heaven be gathered together unto one place, and let the dry land appear: and it was so. And God called the dry land Earth . ."

The suggestion that human activity may someday be able to cultivate other worlds, bringing forth vegetation and animal life on a worldwide scale, may in the perspective of the Bible reading appear presumptuous, even blasphemous. Yet it is only a logical evolution of human activity over the millennia, different only in scale from earlier activities.

Rebuilding Environments
Since human beings first huddled around a campfire, or patched together protective garments against sun or cold, they have sought to live in environments for which their naked bodies were not designed. The aqualung and the oxygen mask are modern technological extensions of this basic principle. Philosophers and anthropologists often mark the beginnings of human intelligence at that point in dim prehistory when human beings began to deliberately alter their external conditions or environments, rather than passively accept the physical environment by changing and evolving their physical selves. After that conceptual break- through, the march from scraped animal hides and campfires to spacesuits and life support systems was merely one of technology, not concept.

The external environments which have been altered by human ac- tivities have grown in scope, from the warmth of a cave to the clearing of a forested valley, then to a regional scale of terraced hillsides, drained swamps, and eroded countrysides. To make life more comfortable, or to open new regions to habitation, people have diverted rivers, tried to make the rain fall, pushed back the sea, destroyed and rebuilt native ecologies, and thrown mountains into marshes. And by accident, unintentionally and in ignorance, human activities have made deserts, wiped out local natural balances, and polluted rivers, lakes, and estuaries.

This philosophy of environmental modification for human gain is hound to continue, on Earth and off. Tempered by lessons learned from unforeseen consequences of environmental abuse on Earth (primarily due to illusions about the unlimited ability of Earth to endure pollution and to provide material resources), humanity can carve out new lands for human settlement, whether on the Matto Grasso or on Mars; the Tibetan Plateau or Venus; the ocean bottom or the Moon; the Gobi or Ganymede.

The other worlds, potential candidates for new homes for humanity, are presently inhospitable to unprotected human bodies. So when human beings first venture there, they will fashion protective garments, and artificially warm their shelters, and carry their own supplies. So it was in the first moments of human history, when the first ventures were made into inhospitable lands; the process continues today with expeditions to the antarctic and the ocean floor. This inhospitality, in space as on Earth, is not a barrier, only a difficulty. The universe is not actively hostile, merely neutral, and subject (as always) to the consequences of deliberate human manipulation. If the challenges are greater and on a grander scale, then so too will be tomorrow's human skills, powers, and ingenuity.

Rebuilding Planets
Now let us conjure up the visions of planetary engineering. Imagine the terraforming of new worlds in space. When once long ago, fertile valleys needed irrigation, now whole planets lie dry but potentially fertile. Where once caves were warmed, now whole worlds lie ready for thermal manipulation.

Imagine the misnamed "maria" of the Moon filled with water, and the dry rilles doused with torrents from mountain thunderstorms, as the clouds of the new blue lunar skies increase the full Moon's brightness manyfold, casting starker shadows back on Earth. Imagine the pink skies of Mars turned dark blue, and the red rocks tinged with the dark green of algae, as the permafrost buried in a tomb of eons is melted to carve new flood channels and to roam again through the humid skies. Imagine the hell-planet Venus brought to truly deserve its name as the "twin of Earth," with its suffocating atmosphere locked safely away or dispersed into space, with its months-long "day" repaired, and with a new Earth- like magnetic field gaining strength to ward off solar radiation, Imagine Mercury, shielded and watered, a home for human beings. Imagine the newly probed giant moons of Jupiter and Saturn and Neptune, warmed, sculpted, and watered for settlement.

Caption: Since many potential new Earths lack atmospheres and oceans, the necessary volatile material must be imported from elsewhere in the Solar System. Here, "ice-teroids" (a term coined by artist David Egge) from beyond Jupiter smash into the formerly dry surface of one such world-perhaps the Moon or Mars or Mercury.

Imagine the depths of space, 100 million kilometers from any planet, teeming with artificial settlements carrying millions of our not-too-distant descendants, Imagine the foreboding Jovian gas giants, distilled down for their essences, their rocks to form new Earths and their gases to power thirtieth century machines. Lastly, imagine Earth, birth world but no longer prison world of the human race, made deliberately into the par- adise people have always sought, but which has always existed only in the eternal imaginations of all-too-mortal minds.

Beyond Earth there lie numerous planets, even more numerous moons, and innumerable asteroids, comets, meteor swarms, and similar debris. Some of these bodies consist of rocky and metallic material, while others are mostly formed of volatile gases and ices. And, of course, there are various gradations of mixtures. All are lit and heated by the nuclear fires of the Sun; some have their own internal heat sources as well.

Through terraforming, mankind will rearrange these physical objects, altering their movements and radiation balances, breaking them up or pushing them together, in order to create Earth-like worlds. Even here the definition of "Earth-like" is still unresolvable; the best we can say is that these rebuilt worlds will be capable of supporting Earth-derived life, including people, without significant restrictions.

The major players in this Solar System reconstruction project will, of course, be the large planets upon which we will try to create habitable environments. Mars and Venus are obvious first choices, with the Moon and Mercury coming along later. Satellites of the Jovian planets have the right size for a sufficiently large gravity field, but their compositions are not always appropriate; such candidates as Io, Europa, Ganymede, Cal- listo, Titan, Triton, and the Pluto-Charon duet need to be individually considered.

Mars, as the Mariner and Viking probes have shown us, is small and cold with a too-thin atmosphere and an absence of detectable amounts of liquid water. However, the planet is probably the best candidate for the first terraforming target. There is plentiful evidence that great supplies of water are frozen beneath the surface; there are several different schemes for warming the planet to the point that its new climate could be self-sustaining; terrestrial organisms could be seeded there to help convert the atmosphere. We shall examine how all this can be done-along with several technological roadblocks not widely recog- nized-in two full chapters.

Venus deserves a chapter all its own because of its former reputation as a "twin" of Earth, and its present status as "the best model of classical visions of Hell known in the Solar System." Some of the oldest serious suggestions of terraforming planets dealt with the possibility of rebuilding Venus, but new developments have dealt serious blows to the feasibility of such proposals. While Mars may turn out to be easier to terraform than we had once thought, Venus will probably be that much more difficult.

Perhaps half a dozen smaller, airless worlds are also candidates for terraforming, although wide ranges of solar intensity must be dealt with, and the entire mass of the atmosphere would probably have to be im- ported. In a chapter devoted to the Moon, Mercury, lo, and similar worlds, we'll look at the individual problems of each, compared to the tools and techniques and cunning which will, by then, be available.

The giant Jovian planets-Jupiter, Saturn, Uranus, and Neptune - consist of tremendous amounts of gases such as hydrogen, helium, methane, and ammonia, together with rocky cores several times the size of Earth. At first glance, it seems their powerful gravity keeps these ma- terials safe beyond human reach-but only at first glance.

This leaves the smaller moons, the asteroids, and the comets. Since they cannot be converted into Earth-like worlds, they can be considered raw materials to he used in the conversion of the more likely targets, the rocky planets. Their primary use will be to provide volatile materials for atmospheres, since such bodies consist (to varying degrees) of water-ice, nitrogen compounds, and similar necessary ingredients. We will need much better knowledge of their compositions in order to decide which ones are the best to use.

Rebuilding Earth
Terraforming has a great deal of promise even if we never consider other planets at all. The climate of Earth itself may need to be preserved against natural disaster by means of terraforming.

For example, it is now generally accepted that our home world is at present deep in an Ice Age, of which we are temporarily experiencing direction and in intensity, and it mysteriously reverses its polarity pe- riodically-with disturbing ecological consequences, including the ex- tinction of species. The flux of cosmic radiation can be vastly increased by the appearance of nearby supernovas, bathing Earth's surface in mu- tagenic and carcinogenic radiation for decades at a time, and hiding underground may not help, since the radiation would completely overturn natural atmospheric cycles involving nitrogen, ozone, and other gases.

All of these changes and disasters have been going on for millions and billions of years, and terrestrial life has apparently repeatedly been subjected to climatic catastrophes. Now Earth is hosting a life form-homo sapiens-whose current civilization is probably not suffi- ciently elastic to tolerate any repetition of these typical events. If, or rather, when these disasters happen again, civilization could very well be destroyed.

Or maybe not. Homo sapiens is the first terrestrial species to have an alternative; they can learn how to step in and interfere, so as to control or mitigate these natural variations and factors. Human civilization can act as warden to its entire planet, and must do so if long-term survival is to be the goal.

If these ideas seem too far-fetched for serious consideration (in this century at least), they can be shown to be otherwise. As we shall see, rebuilding planets (including our own) is feasible even if we are restricted to technologies and techniques within the range of our late twentieth century imaginations.

As a demonstration, consider some technologies which are really at the outer limits of present possibilities.

Imagine manipulations of subatomic particle physics which allow the conversion of small asteroids and moonlets into miniature suns via the unleashing of runaway nuclear reactions fuelled by the objects' own substance. Arthur C. Clarke and Krafft Ehricke have both independently described such a trick, and they have both realized the uses to which such miniature suns could be put orbiting worlds in the dark, cold, outer Solar System.

Imagine mono-molecular films of fantastic strength, useful for build- ing airtight roofs over celestial objects whose natural gravity is insufficient to long retain a gaseous envelope.

Imagine true artificial gravity-not the pseudogravity of spinning space- craft where momentum masquerades as mock weight-but authentic inverse-square-law attractive forces which can be turned on and off via the application of energy and ingenuity. Such a device (and its logical consequent, true antigravity) would open the entire Solar System to hu- man occupation, and as an architectural feature of deep-space habitats (each with their own external atmospheres and minature sunlets), such a device could provide homes for the vast majority of our descendants, making living on planets as archaic as living in caves. Earth's surface could be reserved for archeologists, tourists, and a few hermits.

Imagine the opposite of artificial miniature suns-an artificial energy sink-which absorbs radiation indefinitely, providing the means of dis- sipating radiation belts, supernova blasts, and locally, the heat of the Sun itself so that manned probes could reach and enter the interior of our local hearth-star, or even the interior of Earth itself in search of knowledge and riches.

Imagine distant, unreachable planets (perhaps even other stars) as targets for remote-controlled biological terraforming, as canisters of spores are launched by a gigantic, interplanetary electromagnetic cannon on voyages lasting centuries or millennia, so that by the time human settlers arrive, the waiting planets will have developed to the point where the colonists can land safely.

Imagine stars themselves as objects to be engineered, first in order to modulate their energy outputs by alternately banking and stoking their nuclear fires, and ultimately as sources of raw material for the construction of Sun-like stars with useful energy outputs and lifetimes (stars could be mined by detonating them or colliding them, and then sweeping up the ashes).

Imagine entire self-contained worlds, stellar systems, or even glob- ular clusters propelled across intergalactic gulfs on voyages of curiosity, conquest, or retreat-with ultimate arrival a million years or more in the future.

Now relax. These stupendous technologies have been deliberately conjured up for several reasons. The first reason is to make tame planetary engineering-the subject of this book-seem less mind-boggling in com- parison, and to demonstrate that after a thousand years of terraforming the solar system, our descendants are going to have even bigger projects to tackle. The second reason is to show how the concept of terraforming impacts (often in a subtle way) upon most other topics of modern space technology and theory.

Take "SETI"-the search for extraterrestrial intelligence-as an ex- ample. Terraforming is an important topic here. If there really are alien civilizations loose in the galaxy, they are probably engaged in some form of terraforming, perhaps even in a form far beyond those wild imaginings just presented. As space philosopher Dr. Freeman Dyson has expressed it: "We are searching for extraterrestrial technology, not intelligence. We are not interested in what the average extraterrestrial looks like, but only what the most conspicuous might look like."

Such a civilization might make itself deliberately conspicuous by attempts to broadcast recognizable radiation signals across the galaxy (this is the assumption of current SETI theorists); but equally likely, such a civilization might become evident to Earth science via byproduct energy fluxes and modulations consequent to its planetary and stellar engineering activities. Alternately, we might detect-and hopefully recognize-traces of interstellar spaceprobe exhausts, or echoes of thermonuclear blasts of interstellar wars, or something else.

Another example: theorists have wrestled with the question of the origin of life on Earth, and the possibility that such a process has also occurred elsewhere in the Solar System or in the galaxy. Difficulties connected with describing this "accidental" process under postulated terrestrial conditions five billion years ago have led some scientists to wonder whether life might actually have originated elsewhere-under less hostile conditions, and in an originally simpler form-and then have drifted to Earth as spores; this theory has been dubbed "panspermia." A few people have even suggested that the implantation of life on Earth was deliberately accomplished by some extraterrestrial intelligence; this subtheory has been called "directed panspermia." Such an artificial effort to reshape a planet by biological processing is typical terraforming and the implication is startling: the Earth itself may once have been a target for terraforming.

These manifold speculations are beyond the intended scope of this book. Let us leave such stellar engineering topics for later examination and devote our attention to our own Solar System, our future, and new Earths.

"Copyright 1981, James Oberg, all rights reserved".

New Earths Stackpole, 1981, $19.95; New American Library, 1983, trade paperback, $8.95. This is the world's first non-fiction book about "terraforming", or planetary engineering. Foreword by Jack Williamson; Introduction; Terraforming Manifesto; The Biosphere; How Earth "Happened"; Restructuring Earth; Resources for Terraforming; The Technology; Mars -- A First Look; Mars -- A Closer Look; Venus as a True Twin; The Smaller Worlds; Why? Who? By What Right?; Afterword; Glossary; Bibliography; Index.

Hardcover only, free postage/handling -- $19.95 total. Specify desired dedication for autographing, if any.

Send check or money order to: Soaring Hawk Productions Rt 2 Box 350 Dickinson, Texas 77539

Related Links
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only