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# Afterword: Terraforming Ganymede:

### Science and Technology in
Robert A. Heinlein's Farmer in the Sky
by Dr. Jim Woosley
for Sophia and Jayson

Farmer in the Sky1,2 was Robert A. Heinlein's fourth in the series of juvenile science fiction novels written for Scribner's between 1947 (Rocket Ship Galileo) and 1958 (Have Space Suit—Will Travel).3 Written in 1950 during breaks from script writing and filming of Destination Moon, and with a view towards condensation into a serial on establishing Boy Scout troops in space for the Scouting magazine Boy's Life, the novel tells the story of William "Bill" Lermer, a typical early teenaged hero of the Heinlein juveniles.

Farmer is set in a fictional future partially consistent with several of the other juveniles (as well as some of Mr. Heinlein's adult novels). Population growth continues unabated on an exponential curve on Earth, and the presence of sentient natives of Mars and Venus has encouraged humanity to look further for potential colonization. While Mr. Heinlein was aware of some of the visions for large orbiting space-stations (having included a permanently occupied space station in his earlier novel Space Cadet4), Gerard O'Neil had not yet created the concept of constructed colonies in space, and Mr. Heinlein postulated large-scale human settlement on the surface of Ganymede, Jupiter's largest moon, in prelude to wider colonization within the Jovian system.

The purpose of this essay is to explore the science behind Heinlein's vision of terraforming Ganymede. Along the way, we'll discuss what's known today about Jupiter and its moons, as well as some of the other fundamental science inherent in the story. We'll take a look at what has changed in almost sixty years, and comment on Mr. Heinlein's postulates, right and wrong. And we'll add a little local color about some of the other aspects of the story.

### Jupiter and Ganymede

Farmer in the Sky was written in the pre-dawn of the space age. Most of what was known about Jupiter and the Galilean satellites, including Ganymede, was based purely on optical observations, with whatever chemical knowledge could be gleaned from optical spectroscopy. Radio astronomy was in its infancy, and the discovery of radio emissions from Jupiter lay five years in the future.5 The US launch of Explorer 1 and the discovery of the terrestrial Van Allen belts, essential knowledge for all aspects of particle activity in a planetary magnetic field, lay eight years in the future.6

These discoveries were not available to Mr. Heinlein as he wrote Farmer in 1950. For a representative review of what was known about Jupiter and the Galilean Satellites at the time, I turned to the university library and discovered Peek's book about Jupiter from 1958.7 Other than the astronomical verities, the relevant contents of this book can be summarized as follows:

- • You can make lots and lots and LOTs of pretty pictures of Jupiter and analyze the cloud dynamics endlessly and try to guess model what the planet rotating underneath the clouds looks like.8
- • Spectroscopy can be used to determine some of the molecular constituents of Jupiter's atmosphere (however, ammonia and methane are the only verified constituents as of Peek's writing). Otherwise, based on mathematical modeling, consisting mainly of estimates of planetary density derived from the measured mass and size, the planet is made mostly of hydrogen and helium, with the former solidified at the core but also dominant in the atmosphere. Water and carbon dioxide in solid form are also expected.9
- • It is (in 1958) far too soon to draw any conclusions about Jupiter's radio emissions.10
- • Any astronomer who thinks he can draw conclusions about the surface features of the rapidly moving Galileans satellites is fooling himself.11

Needless to say, Mr. Heinlein had to rely on a lot of guesswork. His conservative concept that the surface of Ganymede was sterile and silica based, and that Ganymede had significant quantities of ice that could be used both for water and, after electrolysis, for atmospheric oxygen, was not unreasonable. Still, as the largest natural satellite in the solar system, larger than the planet Mercury, Ganymede was a natural choice for colonization if Venus and Mars have been bypassed.

Fifty-seven years later, we know much more about Jupiter and the Jovian satellites, from continued telescopic observation with improved instruments including improved radio-telescopes, and from satellite flybys including the two Pioneer missions, the two Voyager missions, and the long-term Galileo observations. But we do not have direct knowledge of any of the Jovian satellites from landers, so much of what we know remains speculative. Books have been written about the Galileo exploration of the Jovian system, such as Fisher's Mission Jupiter,12 an excellent popular summary of the Galileo observations; and the number of web sites maintained by NASA and academic institutions reporting on Galileo is, well, astronomical.13

During the course of its mission, Galileo made two passes by Ganymede (each consisting of two observation programs) in 1996 and 1997.14 One of the first major observations was that Ganymede had its own magnetic field, which interacts with the broader Jovian magnetic field. Photographs also showed that the crust had been subject to extreme stress during Ganymede's geological history, with long fissures and rifts indicating massive geological shifting, together with evidence of meteor and cometary impacts dating to the early days of the solar system. The rifts are tens of kilometers long and the edges separate by heights of up to about 500 meters.

Mathematical modeling—much more sophisticated than scientists of Mr. Heinlein's day had available—has allowed scientists to construct an interior view of Ganymede based on detailed study of gravitational anomalies.15 Ganymede appears to have a solid rocky or metallic core representing half or more of its total diameter (and hence a quarter of its total mass). The mantle is composed of a pressure-softened mixture of water ice and rocky silicates, while the crust is a tens of mile thick layer of hardened water ice and rocky material, with the darker portions of the surface having the larger rocky component. In other words, plate tectonics on Ganymede is a superchilled version of arctic ice breakup on Earth. I am not, however, looking for polar bears or penguins to wander the landscape.

Surface temperatures hover in the -300 to -170 degrees F range under the 30-fold weaker sunlight at Galileo's orbit. Observations of traces of ozone indicate that the moon has a slight atmosphere of oxygen, probably from decomposition of the surface water ice under the incidence of solar radiation, converting to ozone by radiation bombardment just in the terrestrial ionosphere. Galileo is tidally locked to Jupiter—one of the facts known to Mr. Heinlein—with a "year" equal to its day, and just over one standard terrestrial week.

### A Matter of Energy

Early in Farmer, Bill's father George Lermer, an engineer, tells his son "Wherever Man has mass and energy to work with and enough savvy to know how to manipulate them, he can create any environment he needs." Mr. Heinlein postulates in Farmer, just as in the later novel Time for the Stars,16 the development of total matter-to-useful energy conversion as the basis both for propulsion and the energy for terraforming the Jovian moons.

Heinlein's "converters" are not technically described in the story, and there is no inference that he had any fundamental insights (or knowledge of ongoing research) regarding whether this technology would be plausible. He certainly knew something of the status of development of nuclear technology (over and above his forays into the consequences of nuclear weapons,17 "Blowups Happen" had been written four years earlier) and he was undoubtedly familiar with both the theory and experimental status of antimatter and the fictional employment of antimatter.18 On the other hand, popular understanding of antimatter was still almost two decades in the future, as the increasing audience for science fiction created for television first shared Montgomery Scott's concern for his ". . . poor bairns."19

On the other hand, antimatter is hideously expensive to manufacture by current technology, which involves the use of particle accelerators to collide protons and other particles, followed by collection of the rare antiproton produced by this process.20 Mr. Roddenberry never gets around to explaining how the antimatter that runs the Enterprise warp engines is manufactured, either. It's safe to say that a "converter" could not be a conventional particle accelerator which produces antimatter.

So, is such technology possible? Nobody knows for sure, and nobody that I know of is working on it, but there is existing theory which makes the technology at least plausible. One branch of particle physics that gained a lot of currency in the 1980s (though not as much now as the field rushes headlong down the path of string theory)21 has come to be known as preon theory. Preon theory holds that, just as matter reduces to atoms; and atoms to electrons, protons, and neutrons; and protons and neutrons to quarks, it is plausible that there is another layer of particles below quarks, one that might be either related to electrons, or also form a common constituent with electrons. One of the most complete such theories, originally developed by Israeli physicist Haim Harari in 1979,22 postulated two varieties of particles (with corresponding anti-particles) that he called "rishons." The rishon theory has the strong advantage of being rishon-neutral: the precise combination of rishons making up an electron, a proton, a neutron, and an electron anti-neutrino contain precisely enough rishon-anti-rishon pairs to completely annihilate. Thus, manipulated in an appropriate fashion (one not described by the theory, unfortunately), matter formed from rishons could be converted directly into electromagnetic energy. This concept very quickly captured the imagination of science fiction authors; James P. Hogan has accurately described the production of antimatter by such a technology,23 and Vonda McIntyre incorporated it into her explanation of the "Genesis Effect" in the novelization of Star Trek II: The Wrath of Kahn.24

While it appears unlikely that the precise theory developed by Harari is true, it is not implausible that future developments in particle physics will allow the development of a theory, and ultimately an energy conversion technology, based on a set of collectively neutral preons.

Before leaving the concept of power production, one other approach has been suggested for effective energy production at or above the scale of matter-antimatter annihilation: siphoning of energy from the quantum mechanical vacuum, by use of the Casimir effect. Since it is not consistent with the limited technical description in Farmer, and since the capability of power production via this mechanism has been well described by other scientists with ties to science fiction,25,26 I won't address the details of the technology.

Another perspective on extreme energy production, requiring the active spiritual participation of a human being, was the "quantum ramjet" introduced by Spider Robinson in his completion of Mr. Heinlein's Variable Star.27 For story purposes, this concept is not significantly different from Casimir effect energy production; I won't comment on its plausibility other than to say that I was at least willing to suspend my disbelief until much deeper into the story, on a very different point.

### Mass + Energy = ?

Now that we have some background, it's time to look at the technical elements of Heinlein's vision for the terraforming of Ganymede. Those may be summarized as follows:

- • Atmosphere generation (started in 1998, in the novel). Energy conversion was used for thermal decomposition of water ice native to Ganymede, releasing the product gases to the atmosphere. The hydrogen diffuses away to leave an oxygen atmosphere of three pounds per square inch (psi) net pressure at the surface of Ganymede.
- • A "heat trap" operating by the greenhouse effect; however it is not described except to say that it gives off a greenish tint—the color of ionized oxygen—when operating at full strength, that it is operated from the power plant, that it allows light from the Sun (and other sources, such as Jupiter) to pass without allowing significant light or heat to be reflected back into space, and it covers the whole planet.
- • Importing conditioned fertile soil with bacteria and earthworms to work from the conditioned soil (and colony compost) as a base to build fields for soil agriculture from the sterile Ganymede rock.
- • Importing most terrestrial plant foodstocks and edible animals, down to such details as importing bees for pollinization, as well as for honey. Hydroponics was the initial basis for farming, supplemented by soil-grown foodstocks as soil was imported and dirt farmers staked and terraformed claims one acre at a time, with all but the most backbreaking of labor performed by hand.

The colony on Ganymede appears to be based on the economic assumption that each task should be accomplished with the smallest expenditure of mass in transit, regardless of relative efficiency, and subject to the caveat that the planetary engineering apparatus—atmosphere maintenance and the "heat trap"—should have preference. Hence, large earth-moving equipment necessary to break up the soil to develop and extend dirt farming is rare and expensive, personal transportation is almost-non-existent, and farm work that could be done in a matter of days with modern agricultural equipment adapted to Ganymede is instead performed using backbreaking physical labor, with most of the benefits of modern agricultural technology packaged into the expensive conditioned soil and pre-engineered Ganymedean hybrids prior to shipment from earth.

### The Economics of Colonization

There are several economic inconsistencies in Farmer. Given the scale of engineering development necessary to the terraforming of the moon, and the amount of mass necessary to the terraforming apparatus, it seems strange that the moon is struggling with maintaining tractors and rock-crushing equipment. What is not clear, without a great deal of systems analysis (and given the appropriate energy and other supporting technologies), is whether the greatest agricultural productivity comes from moving people to Ganymede, or more equipment. Of course, such an analysis must consider the inherent flexibility of human beings – and the apparent desire of the Colonization Commission to establish Ganymede as a self-sufficient colony prior to the war they anticipate could end Earth's ability to support its colonies in space. The system described, while romantically harkening back to the days of the American frontier, is also well suited to matching agricultural output to available productive manpower.

The greatest inconsistency is related to the development and use of converter technology. Converter technology was used at a very large scale at the start of the Atmosphere Project in 1998. When the Lermers arrive on Ganymede, it is stated that the population is 30,000 people, and that the colony had been assimilating 500 people per year prior to the arrival of 6,000 people on the Mayflower, the first converter technology ship. This implies that the minimum time of colonization was 60 years. Why did it take (at least) 60 years to transition from use of converter technology at the scale necessary to build a breathable atmosphere out of ice, while maintaining the heat trap (however much power that took), to using it for space propulsion? It took about 200 million times more energy to build the atmosphere (using Mr. Heinlein's numbers in Farmer) than to run the Mayflower. This is as the ratio of an ounce of nitroglycerin to the Trinity bomb. Is there something unique about converter technology that caused it to be employed on a planetary engineering scale before it could be scaled down for space propulsion? Or did Mr. Heinlein let this one pass for the sake of his story?

There are other implications of this result. Was the Ganymede colony conceived as much as an isolated demonstration pilot project for a difficult and dangerous power technology as it was for the benefits of having a remote terrestrial colony? Without converter technology, how many trips of scientist and engineers, and equipment sized to move tons of matter per second, were required just to complete the atmosphere project? If the atmosphere project is assumed to have required 20 years to complete, the amount of ice which had to be fed into the atmosphere generation equipment is on the order of a million tons per second, or an ice cube over 100 yards on the side, every second. Together with both the converter and the earth-moving equipment necessary to sustaining that rate of mass flow, day in and day out, for twenty years. And they had trouble transporting farm tractors?

Of course, much hinges on the ability of the "heat trap" to supplement the power generated by the converter station by allowing Ganymede to retain a significantly higher fraction of natural sunlight. The heat trap is the Deus ex machina which allows widespread colonization of the moon without the type of shelter systems that are associated today with Lunar bases. The catch is that it might not help as much as Mr. Heinlein presumes. The blackbody temperature of Ganymede is about -237 degrees F, and eliminating all re-emission of infrared light from solar heating would not raise the average above -16 degrees F.28 It would be warmer in the temperate zones of Ganymede, of course, but a balmy day at the equator is unlikely to exceed freezing by much (presuming that the surface range of temperatures stays constant). One may speculate that the energy which sustains the heat trap, as well as the broadcast power across the planet, is required to provide additional warming—but the sustaining power requirement is enormous.

It should also be noted that, based on what we know about Ganymede today, success in heating the whole moon to a habitable temperature would result in a substantial ocean of water from melted ice, and the possibility of a significant component of ammonia in the atmosphere. The land surface might well be reduced to a few small islands.

One factor which Mr. Heinlein consistently missed in his 1950s novels was the advance in radio communications technology, a failing that he shared with many of his contemporaries. In Farmer, radio transmission from Ganymede to Earth was only possible by relay through Mars and then only under the most favorable conditions, recurring for only a few months every couple of years. Modern unmanned satellites with quite modest antennas are now capable of transmission from the Jupiter system to Earth, and it is inconceivable that a manned outpost or colony on Ganymede would ever be out of touch with Earth for more than hours or days, except in a major emergency.

### Agriculture in the Shade

Sixty years after the writing of Farmer, it is unfortunately safe to say that very few boys of the age that the novel was originally aimed at have ever been on a working farm. Much of the information that Mr. Heinlein portrays about agriculture in small farming communities remains accurate. Unfortunately, the family farm has been largely replaced by the corporate farm, and as suggested above, I suspect that large-scale farming on a terraformed moon within the solar system would be conducted on a corporate rather than a family farm model.

### It's a Gas

The Atmosphere Project first generated an oxygen atmosphere for Ganymede by thermal dissociation of water ice, and at the time of the novel was beginning to work on ammonia to add nitrogen to the atmosphere. There is, unfortunately, at least one problem with this approach: a spark is going to ignite anything organic in its proximity, and the flame will be almost impossible to quench (and might get hot enough to also consume the nascent nitrogen in the atmosphere as well). I don't believe that it is possible to maintain a colony under these conditions; any householder or worker who ignores his electrical grounding is a dead man, sooner or much sooner. Taking more time and generating a balanced oxygen/nitrogen atmosphere with an oxygen partial pressure of under 30 percent is required for both short-term and long-term safety.

### The "Jupiter Effect"

The most dramatic section of the story involves the "moonquake" which is occasioned by an alignment of all Jovian moons with the planet Jupiter and with the sun, triggered by the tectonic stresses associated with the large mass movements of the Atmosphere Project. This consequence is, unfortunately, far too probable due to the high tides of the Jovian system, which subject Europa and Io to solid stresses. Ganymede is somewhat isolated from this by its larger distance from Jupiter, but a tectonic reshuffling after a project of this scale is to be expected, sooner or later.29

### Out in Space

Mr. Heinlein lacked the advantage of modern research of the effects of ionizing radiation in space and its potential effects on human health, which, while certainly overdramatized in the popular media (much less the monster movies spawned by the Atomic Age in the years following Farmer) cannot be neglected in a serious study of long-term space travel. Cosmic radiation was well known, of course, due to its ability to penetrate the atmosphere; but ionizing solar radiation and the accompanying radiation belts, where such radiation is captured in planetary magnetic fields, were completely unknown; and the one aspect of such phenomena observable from the surface of the Earth, the aurora, was poorly understood until well after the discovery of the Van Allen radiation belts.30

Thus, when Bill questions the relatively thin hull of the Mayflower, he is told about radiation cascades and the theory that shipboard radiation dosages are minimized by a thin hull. Modern science realizes that, at least during intense solar activity, shielding must be provided, either in the form of a significant amount of shielding mass or in the form of an electromagnetic field capable of deflecting the radiation, which might present other problems of its own. Given the power available with converter technology, the latter solution would undoubtedly be more elegant, and less expensive, than the necessary shielding mass.

Heinlein postulates "fake rings" of debris in the plane of Jupiter's moons. We now know that all of the giant planets have equatorial ring systems, though the rings of Saturn remain by far the most spectacular.31

### Conclusions

Based on what was known at the time, Farmer in the Sky presents an elegant approach to the terraforming and settlement of the Jovian moons. Some day in the future—and perhaps not that far in the future, if we can develop the supporting energy and propulsion technologies—mankind will follow Heinlein's vision to make use of the mass of Ganymede—and Callisto—and the other Jovian moons. We will have to rely on greater technological protections for the settlement, with emplaced camps and protective shelters (including protection from the ambient radiation trapped by both the Jovian and Ganymedean magnetic fields) such as we are currently discussing for our own moon, but the problems of water (and oxygen) will be much more easily solved on a moon with large quantities of water ice than they will on our own dehydrated satellite.32 And agriculture "under lights" including hydroponics and forced gardens will remain part of the solution. Power will be localized and will undoubtedly be based on a combination of nuclear and solar cells operating from concentrated sunlight for many years—probably for centuries, rather than decades—following the first settlements. Terraforming even so small a moon as Ganymede will not be possible without the vast power that can be delivered by large-scale "converter" or Casimir effect technologies, or the equally audacious ability to build and maneuver in-space solar collectors thousands of kilometers across.

But it's also interesting to look at the things that Heinlein got right, the areas where he had (or had access to) accurate knowledge and the ability to extrapolate from it. The opening chapter features Bill and his father having dinner. Twenty years before the microwave became commonplace, Heinlein predicted frozen convenience foods, "nuked" baked potatoes, and synthetic condiments—all in disposable convenience packaging marked with nutritional information. That detailed sociological projection is just as impressive that the technical details of terraforming a world.

### Acknowledgements

I would like to thank Dr. Conley Powell and Ms. Patricia Taylor for their review of the manuscript and helpful discussion. And a big thanks to Toni Weisskopf for permitting me this opportunity. Any errors, of course, remain mine.

### About the Author

Dr. Woosley, with degrees in physics and astronomy, biophysics, and elementary particle physics, has worked in industrial and flight systems safety, among related projects, for the past two decades.

* * *

1 Citations for first editions of Mr. Heinlein's writings are taken from the Bibliography found in Robert A. Heinlein, edited by Virginia Heinlein, Grumbles from the Grave. New York: Ballantine/Del Rey, 1989.

2 Robert A. Heinlein, Farmer in the Sky. New York: Scribners, 1950.

3 Grumbles from the Grave, Chapter III.

4 Robert A. Heinlein, Space Cadet. New York: Scribners, 1948.

5 http://radiojove.gsfc.nasa.gov/library/sci briefs/discovery.html accessed 2008 January 27.

6 http://www.astronautix.com/craft/exporera.htm accessed 2008 January 27. The launch of Explorer 1 occurred on 1958 January 31, fifty years ago this week as I write this.

7 Bertrand M. Peek, The Planet Jupiter. New York: McMillan, 1958.

8 Peek, ibid, Chapters 1- 20.

9 Peek, ibid., Chapters 21-4, 26-7.

10 Peek, ibid., Chapter 25.

11 Peek, ibid., Chapters 30-31.

12 Daniel Fischer, Mission Jupiter: The Spectacular Journey of the Galileo Spacecraft. New York: Copernicus (Springer Verlag), 2001.

13 The Official NASA Web site for Galileo is at the Jet Propulsion Laboratory, "Galileo Project Home." http://www2.jpl.nasa.gov/galileo/ as of 2008 January 29.

14 http://www2.jpl.nasa.gov/galileo/quick look.html accessed 2008 January 29.

15 http://www.resa.net/nasa/ganymede.htm; http://www.solarviews.com/eng/ganymede.htm; accessed 2008 January 29.

16 Robert A. Heinlein, Time for the Stars. New York: Scribners,

17 Nuclear Essays from Expanded Universe.

18 Robert A. Heinlein, Expanded Universe. New York: Ace Books, 1980 (Reprinted: Baen Books, 2003).

19 Star Trek. NBC Television, 1966-1969.

20 Anti-matter synthesis by modern technology is discussed extensively in Robert Forward in Mirror Matter.

21 Lee Smolin, The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next. Houghton Mifflin, 2006.

22 Haim Harari, A Schematic Model of Quarks and Leptons. Stanford Linear Accelerator Lab (SLAC) Report SLAC-PUB-2310, April, 1979; "The Structure of Quarks and Leptons," Scientific American, April 1983; reprinted in Richard A. Carrigan, Jr. and W. Peter Trower, editors, Particles and Forces: At the Heart of Matter. New York: Freeman, 1990

23 James P. Hogan, Voyage from Yesteryear. New York: Ballantine, 1982.

24 Vonda McIntyre, Star Trek II: The Wrath of Khan. New York: Pocket Books, 1982.

25 Robert F. Forward, "Extracting electrical energy from the vacuum by cohesion of charged foliated conductors." Physics Review B, Volume 30, Number 4, page 1700, 1984 August 15. Archived at http://www.calphysics.org/articles/Forward1984.pdf. This among many excellent technical references on this application of the Casimir force by Dr. Forward and others.

26 Dr. Travis Taylor, Warp Speed. Riverdale, New York: Baen Books, 2004.

27 Robert A. Heinlein, Spider Robinson, Variable Star. Tor, 2006.

28 This assumes a doubling of ambient energy (100% efficiency of the heat trap) and heat content linearly proportional to temperature, the simplest assumption (dQ = cdT). Dr. Conley Powell, in discussion of this point, notes that a run-away greenhouse effect as occurs on Venus could result in substantially higher temperatures, but agrees that it may be very difficult to engineer such an atmosphere for Ganymede and leave a habitable world. It certainly wouldn't be a mostly oxygen, or oxygen/nitrogen, atmosphere.

29 Douglas Cohen (Writer & Director), Laura Verklan (Director) (2008). (Alien Moons) [Television Episode]. In The Universe, (2007-2008). The History Channel.

30 http://en.wikipedia.org/wiki/Aurora %28astronomy%29#History of Aurora theories, accessed 2008 February 2.

31 http://en.wikipedia.org/wiki/Planetary rings, accessed 2008 February 2. Cohen, ibid.

THE END

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