SAE International, Warrendale, PA, 1995. ISBN 1-56091-609-5
Terraforming: Engineering Planetary Environments, by Martyn J. Fogg.
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SAE International, Warrendale, PA, 1995. ISBN 1-56091-609-5 |
Review by Geoffrey A. Landis of the
NASA-Lewis Research Center.
Terraforming is the concept of altering the
environment of a planetary surface to make it suitable for
(terrestrial) life.
The scientific literature about terraforming tends to be sparse, not to mention scattered over a number of journals and books. This book, by British planetologist Martyn Fogg, is an exhaustive book-length review of the scientific literature on terraforming, written at a level that's accessible to the casual (but scientifically-literate) reader. His references are quite thorough, and he is quite meticulous to credit the originator of each idea he mentions, so if you need more, you know where to go to look it up.
It's published, oddly enough, by the Society of Automotive
Engineers. Why the SAE? In explanation, Martyn says, SAE
considers themselves to be first and foremost an engineering
organization, and terraforming--planetary engineering-- is
engineering on the largest scale. Martyn Fogg is a regular writer
of "science fact" articles for Analog, and the book
reads quite smoothly. He starts with a review of the development
of terraforming in science fiction, particularly crediting Olaf
Stapleton with the first lengthy description of terraforming
(Venus, in Last and First Men, 1930), Jack Williamson with
coining the term in 1942 ("Collision Orbit", in
Astounding Science Fiction), and crediting Heinlein with the
first use of terraforming as the background for an entire book,
complete with a quantitative discussion of the energy required,
in Farmer in the Sky (1950). Note that these beat by over a
decade the first scientific discussions of terraforming, Sagan's
proposal to terraform Venus
in 1961, and the proposals to terraform Mars by Burns and Harwit,
and (independently) Sagan, in 1973.
From here, he starts out with a review of how the ecology on a
planet works, paying particular attention to how carbon,
nitrogen, oxygen, phosphorus, and energy cycle through the
system; emphasizing that we are the beneficiaries of a huge
"gratis" energy flow provided by the sun and by
the Earth's tectonic activity, that keeps the environmental
cycles working and acts as an invisible "subsidy" to
the human occupation of the Earth. His next chapter discusses
environmental modifications of the Earth, both incidental, and
deliberate (i.e., solar shields to counter greenhouse
warming.)
Finally, 200 pages into the book, he discusses terraforming other
planets. He starts with Mars, discussing the early (1973) models
of Mars that suggested that, since Mars was once apparently
warmer and wetter than it is now, a small "push" in the
right direction might "snap" Mars into an
alternative, warmer equilibrium due to a runaway greenhouse
effect. To his credit, after a long discussion of the possibility
of "gentle" terraforming of Mars, he then discusses the
very likely case that Mars is not in a such metastable state, and
discusses "hard" terraforming, with a wide analysis of
techniques such as nuclear mining, cometary impact, importing
volatiles from icy moons, and enhancing solar radiation. He
closes with an example terraforming scenario using all the tools
available. Of particular interest is his analysis of time scales.
His terraforming example requires roughly 200 years to reach the
stage where simple anaerobic microorganisms and algae can
survive, and as much as seven thousand years to completely
terraform to a human-breathable atmosphere. A
long term project indeed!
In the following chapter he discusses the much more difficult
problem of terraforming Venus. His discussion of Venus gives an
excellent historical background. When Sagan first proposed
terraforming Venus by "seeding" algae into the clouds
in 1961, Venus was though to be much more
Earthlike than it is now known to be. We now know that the
temperature of Venus is significantly hotter, the atmospheric
pressure tremendously higher, and the chemical environment a lot
harsher, than was thought in the pre-Pioneer days. Venus has just
too damn much atmosphere. He also points
out that, even if it were possible to engineer organisms to
sequester the carbon dioxide from the Venus atmosphere, the
process would take between eleven thousand and 1.1 million years,
depending on how optimistic one is about how efficient
photosynthesis could be made to become. Nevertheless, many
science journalists (e.g., Adrian Berry) have continued to plug
the "easy" terraforming of Venus by "just dropping
a handful of algae into the atmosphere", and Fogg rather
thoroughly debunks their optimism. Terraforming Venus is hard.
His discussion covers most of the
possibilities for dealing with atmosphere of Venus, ranging from
ablating it away with myriad asteroidal impacts, to freezing it
out with solar shields.
The penultimate chapter is on fringe concepts and ultimate
possibilities. He counts terraforming the moon and the larger
satellites of the outer planets under fringe concepts, although
in many ways these
would be considerably easier than some of the other things he
discusses. He then briefly discusses ever further out ideas,
including moving planets, turning Jupiter into a star, and even
the possibility of moving stars. OK. Now to be critical.
The book is billed as the first textbook on the subject of
terraforming. I wouldn't call it a textbook; it reviews the
subject, but doesn't attempt to teach the reader the techniques
of analysis. In other words, having read the book the readers
will be familiar with what has been calculated by others, but
will not have the calculational tools to analyze terraforming
calculations themselves.
In particular, I found the discussion of the greenhouse effect,
critical to an understanding of methods to warm Mars, to be
superficial, barely more thorough than what you might find in the
newspaper. There was no description of methods used to calculate
the amount of greenhouse warming. A description of the greenhouse
effect ought to include spectra, show a formula for integrating
over the spectrum to compute total heat balance, and discuss the
effect of optical depth. The book does not do this, and in fact
never even gives a simplified model to calculate the amount of
greenhouse warming. He does, however, include a useful empirical
equation (unfortunately applicable only to Mars), to calculate
the combined effect of water and CO2 greenhouse effect on overall
surface temperature.
The book suffers a bit from the fact that the illustrations are a
hodgepodge collection of pictures from various articles, with
nomenclature and units inconsistent from one to another.
He skims over the discussion of nitrogen. He claims that an
oxygen atmosphere, even at a few PSI (say, 3 PSI) partial
pressure, requires a nitrogen "buffer" to prevent a
fire hazard. His single reference for this statement, though, is
a rather dubious one. While he does note that this is "a
disputed figure," after this one note he takes the
requirement for 75% of any atmosphere to be nitrogen as a
canonical fact. This is a pity, since it allows him to avoid
asking the tricky question of how little atmospheric nitrogen an
ecosystem actually requires. Nitrogen is a tough problem for
Mars, which is nearly absent of N, as far as we can tell from all
the information we have at the present. Fogg postulates huge
reserves in the form of of nitrate deposits, but I must point out
that there is as yet no real evidence for such deposits, and it
is quite possible that nitrogen on Mars is simply not there.
He has a chapter on planetary engineering of the Earth, which
talks about reversing greenhouse warming by a sun-shield. He
doesn't note that reducing sunlight would also reduce
photosynthesis, and hence enhance the greenhouse effect. (This
could, of course, be ameliorated by a dichroic
shield, which selectively passes the wavelengths most useful for
photosynthesis). I would have liked the flow better if he had put
re-engineering Earth last, with the emphasis that we need to
study,
understand, and experiment, and make our mistakes on other
planets first before embarking to mess with the one we live on.
He could have emphasized how we understand greenhouse effect
based on our studies of Venus; how the "nuclear winter"
scenario was proposed based on studies of the effects of global
dust coverage of Mars.
A small thing that bothered me was that he
doesn't very well distinguish between realistic and far-out
ideas. One of the proposals he discusses, for example, was to
increase the spin of Venus using three
quadrillion objects circulating between Venus and the sun every 2
hours, each traveling at 10% of the speed of light. I would
personally have put that into the "fringe concepts"
section, myself. However, that's only a minor quibble. Fogg uses
the "fringe concepts" pigenhole to discuss the really
far-out concepts.
Despite my carping on minor details, it's a good book. At
forty-nine bucks for a 544 page hardcover, it's a bargain. I
highly recommend it.
Geoffrey A. Landis
Ohio Aerospace Institute at NASA Lewis Research Center
http://www.oai.org/SRA/g_landis.html
Another review of this book by Jeff
Foust and Harold Hamblet
Read the Foreword by Professor Robert Haynes.
Note: This book has just gone out of print. It appears that the only copies now available are second hand. Such copies can be tracked down via Amazon.com.