S CIENCE’ S C OMPASS 65 describes. Was she attributing emotions tense interest to exobiologists and plane- 64 such as fear, joy, and anger, etc., on the ba- tary scientists for more than three decades. 63 sis of morphological similarity to the hu- Such considerations convinced European 62 man repertoire or on the basis of other governments and the United States to fund Image not 61 contexts (as, for example, we do when de- the Cassini- project at a total cost 60 ciding the meaning of an alien expression of approximately $3 billion. The book doc- available for 59 like a cat’s purr)? This is a fundamental uments what is so special about , and online use. 58 omission. Indeed, a final major value of what researchers hope to accomplish after 57 Infant Chimpanzee and Human Child is Cassini reaches Saturn in 2004 and after 56 that today’s students and other thoughtful the Huygens probe enters Titan’s atmo- 55 readers should find in it an intriguing chal- sphere the next year. 54 lenge: Much might be gained by convinc- Author Ralph Lorenz started with the 53 ingly filling the gap between the richness Huygens project as an engineer. After re- 52 of the objective descriptions laid so gener- turning to university to obtain his doctorate, 51 ously before them and the justification of he rejoined the project as a scientist, with 50 legitimate bases for ascribing particular an accompanying demotion from business Smoggy moon. The hydrocarbons in Titan’s 49 states of emotion to these behaviors. class travel to discount economy travel. atmosphere give the moon an orange hue. 48 Lorenz’s experiences, amplified in passages 47 labeled “Ralph’s Log,” lend the book a per- be glossed over. For example, the authors are 46 BOOKS: PLANETARY SCIENCE sonal flavor and give the reader insight into forced to omit many important details that a 45 the inner workings of these complex mis- historian writing on the Cassini-Huygens mis- 44 Photochemical sions. Coauthor Jacqueline Mitton is an as- sion would want for background. Some of us 43 trophysicist, who now devotes her time to consider it a miracle that a spacecraft was de- 42 Smog Hides an writing and media consulting in the field of livered and launched, because ESA and 41 astronomy. Their prose is, accordingly, live- NASA entered this cooperative mission in the 40 Icy World ly and captivating. “sink or swim together” mode. The book has 39 The book begins with a brief historical very few glaring errors of the magnitude of Darrell F. Strobel 38 sketch that covers the 1655 discovery of the claim that “Voyager 1 reached Saturn in 37 ifting Titan’s Veil is an account of the Titan by the Dutch scientist Christiaan November 1980 after a journey lasting just 36 exploration of Titan, Saturn’s largest Huygens and essential aspects of planetary over 13 years,” which would be news to all 35 Lmoon, and the joint effort by the Euro- science (especially the satellites of Jupiter who viewed the launch in the fall of 1977. 34 pean Space Agency (ESA) and NASA to and Saturn). In the early 1980s, the scien- Even the 2600-kg Cassini spacecraft, which 33 reveal its secrets with the Cassini-Huygens tific discoveries of the two Voyager space- needed three gravity assists by and 32 mission. Why Titan? It is the solar system’s craft rewrote the textbooks on Titan by re- before going on to Jupiter, will take on- 31 second largest moon, with a radius about vealing a world completely shrouded in a ly seven years to reach Saturn. On a more irri- 30 60 km smaller than that of Jupiter’s photochemical haze. This smog elevates tating level, I found the rekindling of the de- 29 Ganymede. Whereas Ganymede’s atmo- Titan’s optical limb (the edge of its visible bate on the level of methane saturation at the 28 sphere is measured in picobars (10–12 times disk) some 200 km above the surface and tropopause and in the stratosphere (which I 27 the surface pressure of Earth’s atmo- prevented the Voyager cameras from see- and my colleagues Michael Summers and 26 sphere), the nitrogen atmo- ing the surface. Although the Xun Zhu had sparked in a 1992 paper in 25 sphere of Titan is about 1.5 Lifting Titan’s Veil Hubble Space Telescope and Icarus) attributed to a French colleague, Régis 24 bar. What really distinguishes Exploring the Giant adaptive optics on the largest Courtin. (During a 1993–94 Paris sabbatical, I 23 Titan’s atmosphere is its mildly Moon of Saturn ground-based telescopes have had convinced Régis to reanalyze infrared da- 22 offered glimpses of what might ta from the Voyager missions.) reducing character, conditions by Ralph Lorenz and 21 similar to those many believe Jacqueline Mitton be on Titan’s surface, the part- The authors present some material at 20 characterized Earth’s prebiotic ing of this veil will fall to the the level of Scientific American or Sky and 19 atmosphere, and its large suite Cambridge University Huygens probe and to the Telescope, but most of the text would be 18 of hydrocarbons, organic Press, Cambridge, 2002. radar and remote sensing sys- appropriate in an introduction to astronomy 17 268 pp. $29, £19.95. molecules, and nitriles. Among ISBN 0-521-79348-3. tems on the Cassini spacecraft. for nonscientists. Consequently, the book is 16 the nitriles, hydrogen cyanide The last third of the book is accessible to a wide audience despite a few 15 is a known precursor of α- devoted to this mission: its figures, taken from research articles, that 14 amino acids and nucleic-acid bases; thus, genesis, political aspects, design and con- might not be understood by all readers. 13 Titan’s environment is of great importance struction, launch, operations; the plans for And even the professional scientist who 12 for understanding chemical evolution in probing Titan and touring the Saturn sys- wants a brief overview on Titan or an ab- 11 Earth’s early atmosphere. Present-day Titan tem; and the problems with the radio relay breviated history of the Cassini-Huygens 10 could be a natural laboratory for chemical that link Huygens with Cassini. mission will find the book worthwhile. 9 synthesis analogous to the pioneering labo- The authors also provide interesting I recommend Lifting Titan’s Veil to anyone 8 ratory experiments on the origin of life that discussions about what the mission may having an interest in planetary exploration. 7 Urey and Miller carried out in the 1950s. reveal. Titan’s atmosphere, , With fewer than two years remaining until 6 As a result, Titan has been an object of in- and landscape each merit a chapter in the the arrival of the Cassini spacecraft and its 5 book. Based on our current knowledge, insertion into orbit around Saturn, however, 4 these chapters represent a progression the book comes with a sunset clause. We The author is in the Department of Earth and Plane- 3 tary Sciences, The Johns Hopkins University, 3400 N. from fact to speculation. expect exciting new discoveries and look 2 Charles Street, Baltimore, MD 21218–2687, USA. E- The economy of presentation required by forward to the authors reporting them in an

1 2/NASA CREDIT:VOYAGER mail: [email protected] the book’s brief length means that details must equally informative sequel.

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