Gr 9-12 Fisher's answer to the question, ``Is there life on Mars?'' is an unequivocal ``I don't know.'' Of course, no absolutely certain answer can be made on the basis of the available evidence, as is explained in a discussion of what constitutes scientific proof. However, the structure of this study leads readers to expect a definitive conclusion, and Fisher's failure to take a stand either way is a letdown. Fisher first examines the underlying assumptions concerning the nature of life and why it is reasonable to look for life on Mars. This section serves as a primer on evolution and cellular chemistry. The development of the three biological experiments carried by the Viking spacecrafts to test for life is covered in detail, and the results are meticulously analyzed. (The controversial ``third experiment'' produced the greatest evidence for what might be life.) This account is an excellent illustration of the application of the scientific method. Unfortunately, in attempting to appeal to younger readers, Fisher constantly interrupts his report with asides of adolescent babble. This does not make the subject matter any easier to understand and will distract to older readers. On the opposite extreme, there are many allusions, mostly poetic, which will be lost even on senior high students. Some might object to the human chauvinism Fisher espouses to justify space exploration. The illustrations are simple and adequate. Persistent researchers will be amply rewarded with detail, but they will have to endure much which is extraneous to the central purpose. Dennis Ford, Canandaigua Junior Academy Library, N.Y.