The Search for Life on Mars

If all goes well, in 2003 two highly evolved descendants of the Sojourner ""rover"" that scuttled around Mars in 1997 will return to the planet and collect new samples. NASA scientists will then scrutinize these souvenirs for evidence of extraterrestrial life. But considering the cost of the trip, where should NASA concentrate its search? A paleontologist at the University of Sydney, Australia, who has been involved with NASA's Mars missions for more than a decade, Walter analyzes the conditions surrounding the emergence of life on earth to suggest the most likely locations of Martian fossils. Three and a half billion years ago, water was as plentiful on Mars as on earth. Scientists believe that vast quantities of water (the prerequisite for life as we know it) still exist on Mars, not only at the poles but also in an underground layer of permafrost. And in the last few decades, scientists have discovered vast numbers of micro-organisms living inside earth's rocks, far underground and around thermal springs, environments that were once considered too inhospitable to support life. Thus, Walter proposes that, despite Mars's harsh climate, fossils and living organisms might be found in three environments: former lake beds, spring deposits and microbe-produced ore deposits similar to the silver, lead and zinc deposits in northern Australia. Though Walter's concluding section on the importance of space research is weak and his exposition occasionally rambles, his chapters on paleontology, microbiology and geology are refreshingly lucid. Illustrations not seen by PW. (Nov.)