Physics and Chemistry of the Solar System
by John S. Lewis
Academic Press, San Diego, 1995, 556 pp.
Hardcover, $149.00; softcover, $69.95

It is common for books whose titles suggest great scope--such as this one surely does--to contain acknowledgments to those who read and reviewed various chapters: The subject matter is just too broad for any one of us to be confident of getting it all right by ourselves. This book contains no such acknowledgments. Although I cannot be sure of the significance of that lack, I guess that no such reviews were requested. This could be the reason that the book suffers from considerable imbalance, omission, and error, but nonetheless contains a lot of information on some topics, presented in prose that is generally interesting and clear. As the intended target, according to the author, comprises upper-level undergraduates, graduate students, and practicing scientists wanting a broader context, the imbalance appears to me to be a serious flaw. The book covers ground from galaxies to the Sun and its nebula, to the major planets and their satellites, to small bodies, to the terrestrial planets, to atmospheres, and to life here and elsewhere, and so should be of general interest. Yet it is a clear demonstration of the dangers of writing outside the field of one's own expertise.

Lewis' expertise is nebular condensations, atmospheres, and theoretical modeling, not the analysis of materials at sample or orbital scales. The sections about the Sun and the solar nebula, about the major planets, and about the atmospheres of the larger terrestrial planets are thus full and the known parameters and models well covered. They have generous helpings of equations and derivations and lots of plots showing how things behave, or how theorists think they should behave--for me at least, the helpings were too generous. Similarly, the perspective on nucleosynthesis is more than adequate for a book of the stated purpose. Some things will be confusing at the introductory level--for instance, a table of elemental abundances of the solar system has no units, and it is not stated that the abundances (mass, or number of atoms??) are normalized to silicon. The actual units are well known to those in the business but surely not to others. These chapters have a much greater emphasis on the chemistry than on what I might consider the physics, but subjects such as "Radio Wave Propagation in Space Plasmas" are included. The chapter "Comets and Meteors" appears to me to be a balanced introduction to both physics and chemistry, and is up-to-date enough to include some discussion of the Shoemaker-Levy 9 collisions with Jupiter.

In the fields outside Lewis' main interests, however, the book falls short. Thus whereas trace elements including the rare earths have assumed a prominent role in planetary geochemistry papers over the last couple of decades, not a single rare earth diagram appears in this book, and their use in tracing mantle characteristics and processes is absent. Similarly absent is the use of radiogenic isotopes as tracers, and element tracers of core formations and crust-mantle separation. And there is no related experimental petrology either; petrology is limited to stating the concepts of Bowen from 50 years ago. Considering the amount of attention and discussion given to petrogenesis and differentiation of terrestrial planets by magma oceans over the last two decades, the absence of any discussion of the physics of magma oceans, even in the section about our Moon, is a mistake. Missing from the index are the likes of neutron activation, partition coefficients, the rare earth elements (as a group or as individuals), magma ocean, and either core or core formation. There is no discussion of analytical techniques, so that mass spectrometry, electron microprobes, and X-ray fluorescence are out. Interferometry is in, presumably because it is a planetary astronomy technique and obtains atmospheric molecule data.

The Earth is intentionally left until late (in the introduction we are told this is to defer its complexity; when we get to it, we are told this is to minimize the tendency to anthropomorphize). Yet, despite what Lewis might wish, the Earth--and, since the Apollo voyages, the Moon--provides our greatest source of information, our most keen insights into what planets are, and our testbeds for the creative speculations of planetary theorists. Lewis seems to be painfully unaware that our understanding of the Moon gained through the Apollo program has greatly influenced our view of all other planets. Yet he devotes as much space to each of Io, rings, and the Venus atmosphere and its possible interaction with the venusian surface--all based on an incredibly small and unreliable database--as he does to the entire Moon. The discussion of Earth's history includes a misunderstanding of the basis of stratigraphic division, an erroneous view of what an early Catastrophist was, and a garbled description of Darwin's natural selection mechanism that omits variation from its basis and even suggests that Darwin and his contemporaries knew about genes (though this is probably just poor wording).

The current lull in planetary missions, says the author, is one inspiration to write this book--to avoid instant obsolescence. I cannot judge the entire contents of the book in this regard, but the Moon chapter would have been obsolete and error-ridden 20 years ago. I have mentioned the omission of magma oceans, an important paradigm in many lunar studies. Not only is the Clementine mission omitted (perhaps forgiveably as it is so recent, but Shoemaker-Levy 9 was later still and is included), but the only table of chemical analyses is Surveyor data! We are told that mare basalts have refractory elements such as U and the rare earths enriched compared with CI chondrites by a factor of about 100, when in reality only a rare few approach such perilous heights. The only reference to radiometric ages, an important basis for understanding lunar history, comes almost irrelevantly in a section on magnetics. According to this book, fine-grained basalts are called Type A and coarse-grained ones Type B, which is a holdover from Apollo 11 that was rapidly replaced by more fundamental chemical groupings. Supposedly both types show abundant vesicles (that is just wrong!). A diagram of mare basalt pyroxenes is imaginary and misleading. A list of "the most important lunar minerals" includes graphite and perovskite (their existence on the Moon has never been substantiated), and native copper, chalcopyrite, and quartz that are extremely rare (I have never seen them in 20 years of studying lunar thin sections). Olivine, a fundamental mineral in petrogenesis, is relegated to the role of a minor mineral. We are told that the highlands are dominated by anorthosites (an exaggeration) and anorthitic pyroxenites (a garbled term, and whatever they are, they do not exist in the lunar sample collection). Remote sensing of the Moon is virtually ignored. Virtually no discussion whatsoever is given to large multiring basins (not in the index) anywhere in the solar system. We are told that they are similar in appearance to ripples in water (!!!), when such an analogy is pointless in substance, erroneous in reality, and misleading in concept. Rings are scarps that have steep sharp inner slopes and gentle outer slopes, caused by faulting that is absent in ripples.

This book would have been improved by a coherent discussion of the bulk chemical compositions of the planets. While some bulk chemical properties are given, scattered about the book, this does not apply to the major elements. Some import is attached to an elevated FeO for the Moon, especially for its origin, but there is no discussion of the derivation or reality or even the magnitude of this "fact." Tables of our best estimates for the bulk compositions of the terrestrial planets, and the basis for those estimates, would have been extremely useful for those trying to acquire a general knowledge of the solar system.

For the subject matter with which I am most familiar, including impacts, meteorites (so little on the martian meteorites or the eucrite family!), and the geology and chemistry of the terrestrial planets, this book is sadly lacking. Given that the author is part of an institution with considerable expertise in solar system chemistry and physics, including sample analysis and impact mechanics, I find it surprising that the book has such imbalances and errors as it does. I would recommend other works to satisfy a desire for knowledge about the physics and geochemistry of at least the solid planets, including S. R. Taylor's Solar System Evolution (Cambridge University Press, 1992). The book does not include running references, but has suggested general and review readings for each chapter. Strangely, those for the Moon do not include The Lunar Sourcebook (eds. G. Heiken, D. Vaniman, and B. French; Cambridge University Press, 1991), an up-to-date mine of lunar chemical and physical information.

--Graham Ryder

(Dr. Ryder is a Staff Scientist at LPI)