The planet Marscrimson and bright, filling our telescopes with vague intimations of almost-familiar landformshas long formed a celestial tabula rasa on which we have inscribed our planetological theories, utopian fantasies, and fears of alien invasion or ecological ruin. In the past few years we have been begun inscribing something new in the sands of Mars: tire tracks. Two recent books come at the planet from very different perspectives. In Roving Mars, Steve Squyres gives us a vivid, intimate travelogue of the spectacularly successful (and as of this writing, ongoing) mission of the Mars Exploration Rovers, for which he serves as principal investigator. Robert Markleys Dying Planet takes a more distant view of the human relationship with Mars. An English professor at the University of Illinois, Markley writes about Mars science as a knowledgeable outsider, weaving in cultural history and science fiction. Roving Mars is a page-turner. Squyress writing is clear, with folksy touches, including flashes of dry humor and brief but revealing vignettes illuminating the personalities of a number of the key players. Many books wax eloquent about planetary exploration. Squyres shows how it is actually done. Spirit and Opportunity may not be the best spacecraft names ever, but they do provide the perfect subtitle for this book. We learn just how much spirit, in the form of human ingenuity, perseverance, joy and tears, is distilled into those craft, and how for years opportunity knocked at Squyress door and then quickly ran off and left him, as proposals were rejected, missions were canceled, and NASAs Mars plans went through countless revisions. His perseverance seems quixotic at times, yet he never stopped answering the door, and when opportunity finally came knocking for real, Squyres was given a chance, with a ridiculously compressed schedule, to get two rovers built, tested and ready for launch in 34 months. He and his team understandably got attached to the rovers. You, too, will come to identify with the little mechanical puppies as you learn about their troubled gestation, hurried birth and solitary departures. I was initially surprised to find that 65 percent of the book takes place before the fi rst picture is returned from Mars. I came to appreciate this focus on the lesser-known early story. I already thought of Spirit and Opportunity as the "miracle rovers" for their great longevity. But I had no idea. Even though you know that ultimately nothing serious is going to go wrong before they get to Mars, the tale of tribulations is gripping. Working under intense time and budget pressure, the team wrestles with faulty parachutes, defective instruments, flubbed tests, mysterious short circuits, and design flaws discovered as the pages fl y off the calendar toward a launch window that could not be changed, because of the laws of celestial mechanics. I found myself wiping away tears as Squyres described the strange sadness finally evoked by the launch, as he realizes that however it all ends, they aint never coming back home. Roving Mars is often refreshingly candid. Describing a design error that got his teams camera rejected from an earlier mission, he confesses, "With one terrible, boneheaded mistake we had thrown away five years of work." He shares some of the less than exemplary behavior needed to win the game of big science: the artful formation of science teams put together, in part, to neutralize the competition, the changing of mission designs to win over potential reviewers, and the sometimes brutal necessity of competing ruthlessly against ones long-time friends and colleagues. He also writes revealingly about the tense battles pitting "the idealistic, impractical scientists against the stubborn, practical engineers." This disarming honesty is one of the aspects of the book I appreciate the most. What are they going to do now, take his mission away? Squyres can tell it like it is because he has succeeded. A very different perspective on the culture of science can be found in Dying Planet. This book is not a page-turner. The style is hyperacademic and wordy. As a scientist, I found Markleys approach, which examines science as a cultural enterprise and critically dissects our language, methods and beliefs, to be both enlightening and occasionally annoyingthe latter mostly when the language became opaque and the analysis long-winded. The amount of serious scrutiny devoted to mediocre (but fun) films like Total Recall overestimates their importance as barometers of societal views and attitudes about the human future on Mars. The book is also sprinkled with numerous small but irritating errors that would have been caught in a careful once-over by a planetary scientist. But if you can deal with occasional passages about bringing Mars "within the semiotics of historical and experiential time" and "the ways in which Mars exists as a complex multidisciplinary object," there are many historical, literary, political and cultural nuggetsin particular, a reanalysis of the lingering impact on planetary science of the Martian canal theory of Percival Lowell, a planetologist who early in the 20th century suggested that the lines visible on Mars were the engineering works of an advanced race struggling to irrigate their drying, dying world. Whereas previous writers have suggested that Lowells influence quickly waned after 1920, Markley argues that this standard account "underestimates the ways in which Lowells paradigm of a dying planet influenced scientific speculation about the composition of the Martian atmosphere, the character of its surface, and the nature of its putative life-forms." The idea of the canals, and of a relatively wet and clement Mars, persisted in scientific discourse up to, an even into, the Space Age. Markley shows that throughout the 20th century, reputable scientists held out hope for water and plant life on Mars even while spectroscopic evidence of temperature and atmospheric composition suggested otherwise. This history should give us pause today when we rejoice in the latest evidence for a possible bio-friendly Mars. More than a century after Lowells controversial observations, Mars remains the planet that lost its water and, probably, its capacity for life. It is now obvious that Mars cannot be flagrantly alive in the sense that Earth is. Today the question is, Can Mars be at least barely alive, with colonies holding out in underground lakes and hot springs? Possible signs of life continue to be the subject of debate and spur for further observations: 100 years ago it was the canals; 50 years ago, ephemeral hints of chlorophyll were seen and later discredited. Today we see traces of atmospheric methane that just might be the breath of underground survivors. Meanwhile the rocks, mute witnesses to the real Martian story, are beginning to talk under the patient scrutiny of the Mars Exploration Rovers. Markley might have a field day with some of the language in Roving Mars. Squyres seems obsessed with finding a "water story," even to the point of repeatedly implying that the success of each rovers mission hinges on finding concrete evidence of rocks formed in or altered by liquid water. Now of course, "following the water" is important for figuring out the natural history of Mars and whether it might have been more life-friendly in the past. But isnt a robot geologist, especially the first one on a new world, successful if it simply learns any story the rocks have to tell? It doesnt seem quite right to launch an investigation committed to finding a certain answer. Even less so when that answer, "Yes, there was water here, at some uncertain time and for some uncertain duration," basically confirms the paradigm that has been developing since 1971, as Mariner 9 and subsequent orbiters have provided images and global maps showing abundant evidence for flooding and channel formation. Ultimately the tremendous success of this mission goes much deeper than a simple verification of this widespread belief. Mars has myriad stories to tell. If water is what we seek, then thats what well find. It is obvious that Squyres knows all this, so why the dumbed-down rhetoric, where success is equated with proving a certain hypothesis? This is, in part, playing along with a certain line that NASA is using to package our current Mars exploration program. "Follow the Water" makes a fine slogan, and it does capture the essence of the questions of comparative planetology and habitability, both past and future, that form the core goals of our Mars program. Yet the actual motivations and strategies are never that simple. Given Squyress admirable candor in addressing other aspects of NASA politics, I was surprised to see him uncritically adopt what seems like a simplified motivational mantra when describing the success criteria for his complex, multifaceted mission. Maybe hes just haunted by Lowells ghost. Squyress book ends in September 2004, with Opportunity rooting among the sedimentary rock walls of Endurance crater, and Spirit steadfastly climbing up West Spur in the Columbia hills, where it has finally found some honest-to-goodness bedrock. I am hoping that next year there will be a paperback edition with the further exploits of the miracle rovers and their dogged, intelligent designers.
David Grinspoon is curator of astrobiology at the Denver Museum of Nature and Science and author of Lonely Planets: The Natural Philosophy of Alien Life.