ical activity. Embedded throughout its 

 interior are small globules of carbon- 

 ate materials, along with complex hy- 

 drocarbons called polycyclic aromatic 

 hydrocarbons (PAHs). In terrestrial 

 rocks, carbonates and PAHs are of- 

 ten — though not always — produced 

 by microorganisms. Even more striking 

 was another internal feature of the rock: 

 wormlike tubules, one-hundredth the 

 width of a human hair, which resem- 

 bled Precambrian microfossils that had 

 previously been reported in terrestrial 

 rocks more than 3 billion years old. 



In April 1996 the NASA geologists 

 and their collaborators submitted a pa- 

 per to the prestigious journal Science, 

 titled "Search for Life on Mars: A 

 Study of Martian Meteorites"; three 

 months later the paper was accepted 

 for publication. 



Few papers in Science have drawn 

 such rapt attention. On August 7, 

 1 996, a week before its publication, with 

 leaks about NASA and life on other 

 planets about to appear in the press, Pres- 

 ident Clinton appeared on the South 

 Lawn of the White House to announce 

 the remarkable discovery: "Today, rock 

 eight four oh oh one speaks to us across 

 all those billions of years and millions of 

 miles. If this discovery is confirmed, it 

 will surely be one of the most stunning 

 insights into our universe that science 

 has ever uncovered." 



Kathy Sawyer, a veteran science 

 writer for The Washington Post, de- 

 scribes what happened at the press con- 

 ference immediately following the pres- 

 ident's announcement. ALH84001 

 went into the conference as the 

 celebrity of the day, but it emerged with 

 a reputation as controversial as Michael 

 Jackson's. Daniel Goldin, the dynamic 

 NASA administrator, spoke enthusias- 

 tically of the progress of science, fol- 

 lowed by a sober and detailed presenta- 

 tion of the evidence by McKay and his 

 collaborators. But when the micro- 

 phone passed to an independent com- 

 mentator, "designated skeptic" J. 

 William Schopf, the tone of optimism 

 changed abruptly. Schopf, a UCLA pa- 

 leobiologist, put his assessment bluntly. 



"I think," he told the conference, "a lot 

 more additional work needs to be done 

 before we can have firm confidence that 

 this report is of life on Mars." 



In this expert chronicle of the some- 

 times acrimonious controversy that 

 followed, Sawyer provides a razor- 

 sharp portrait of good science at work. 

 Hers is a story of conscientious inves- 

 tigators using state-of-the-art tech- 

 niques on a problem with no simple 

 resolution, unlike the comedy of er- 

 rors over cold fusion in the 1980s. In- 

 formed observers have still not reached 

 agreement on the "wormlike" features 

 in ALH84001. Some have questioned 

 the supposed biological origin of sim- 

 ilar microfossils in ancient terrestrial 

 rocks. And almost ten years after that 

 August news conference, the "addi- 

 tional work" that Schopf recom- 

 mended continues: on the Antarctic 

 ice sheet, in high-tech laboratories on 

 Earth, and even on Mars itself. 



Men of Salt: Crossing the Sahara 

 on the Caravan ofWltite Gold 



by Michael Benanav 

 The Lyons Press, 2006; $23.95 



What am I doing? Michael Be- 

 nanav asks himself rhetorically, 

 about halfway through this travelogue. 

 "A Jewish guy raised in suburban Con- 

 necticut chasing a camel train across the 

 Sahara . . . just to pick up some salt?" 



The answer is, as the reader soon learns, 

 having a wonderful time. For writers 

 such as Benanav, who like their journeys 

 primal, places where you can have a gen- 

 uine adventure nowadays — out of range 

 of cell phones, soft-drink machines, and 

 caffc macchiatos — are almost impossible to 

 find. But the road from Timbuktu to 

 Taoudenni is certainly one of them. 



Camel caravans regularly travel the 

 route, making the round-trip in about 

 a month. Taoudenni, Mali, situated 

 deep in the Sahara Desert, is as barren 

 as the surface of Mars. Even after trav- 

 eling for days through the Tanezrouft, 

 a part of the desert known to the local 

 Tuareg tribesmen as "The Land of 

 Thirst," Benanav is floored by the ab- 

 solute desolation of its only inhabited 

 location. "[Taoudenni] is situated on 

 utterly lifeless desert flats; not a single 

 leaf, or even thorn, grows from the 

 parched, dusty dirt, which was so sharp 

 it bit into the soles of my bare feet." 



So what draws people to Taoudenni? 

 One word: salt. For centuries enter- 

 prising nomads have led trains of camels 

 there to pick up eighty-pound plates of 

 rock salt chiseled from an ancient seabed 

 by a hardy population of miners. At 

 Taoudenni the heat is hellish, the well 

 water brackish, and the housing little 

 more than a cluster of dirt huts made of 

 rubble from the mines. But Saharan salt 

 brings a good price back in more civi- 

 lized parts, and there aren't many other 

 ways to earn cash in this impoverished 



Young Tuareg men lead a train of camels, laden with slabs of salt, across the 

 Sahara to markets in Timbuktu, Mali. 



March 2006 NATURAL HISTORY 



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