Mapping the Planets

Article excerpt

Mapping the Planets The NASA Atlas of the Solar System, by Ronald Greeley and Raymond A. Batson. Cambridge Univ. Press, $150, 380 pp., illus.

The choicest scientific legacy of the last decade of this millennium is the unambiguous discovery of planets orbiting other stars. At this writing, the total stands at eightnot just eight new planets, but eight new stellar systems alongside our own solar system. Even this tiny sample has revealed new planetary tricks that we had never anticipated, such as giant planets orbiting almost within the central fires of their system, roasting at temperatures of 1,000 kelvin and higher. The lesson is clear: Our solar system, however wide a range of planets we see in it, is but a parochial sample of nature's handiwork.

In the 1960s, the study of Earth introduced us to the idea of a planet as a dynamic, complex, evolving entity and helped us take on the task of understanding the fifteen other planet-sized bodies in the solar system. Since then, geology has given way to comparative planetology, a discipline combining astronomy, geology, meteorology, chemistry, and physics. In turn, planetary research aided strongly in changing the descriptive discipline of geology into the quantitative sciences of geochemistry and geophysics.

Today, after three decades of planetological study of the solar system, we must step out of our little backyard and come face to face with the galaxy at large-with the genesis and ecology of other systems, some of which we know to be wildly unlike our own. The touchstone for this challenge is the solar system. What knowledge and wisdom can we extract from the exploration of the sun's domain to help us in this vastly larger effort?

The NASA Atlas of the Solar System provides an overview of a part of this knowledge, the surface geology of solid solar system bodies. The name "Atlas" is entirely accurate: the book contains more than one hundred large-format pages (12 by 18 inches), from photomosaics to highly interpreted, airbrushed renderings of spacecraft optical imaging and (in the case of perpetually cloudcovered Venus) radar wavelength data. Planets, satellites, and even Ida and Gaspra from the asteroid belt are represented. The only obvious oversight is the absence of the stunning radar images of near-Earth asteroids made by planetary scientist Steve Ostro and his coworkers at NASA's Jet Propulsion Laboratory. Also, enthusiasts of lunar polar ice will not find it mentioned; this work was already in press when the discovery was announced.

But this is not a book of "gosh, geewhiz" pictures. Its strength, its claim to authority, is its presentation of surface geology. …