When NASA researchers from the Johnson Space Center and Stanford University announced they had found combined evidence in 1996 "that strongly suggests primitive life may have existed on Mars more than 3.6 billion years ago," scientists buzzed with excitement at the possibility of life on Mars. Two weeks ago, the discovery of rock-eating microbes one mile beneath the ocean floor (published in the August 14, 1998 issue of Science) seemed to make that possibility more likely. But last week, new evidence based on geochemical models was discovered that indicates that, while basic geological conditions on Mars may meet life's minimal requirements, the biological potential of the red planet seems unlikely. The nine resources listed provide background information, specifics, and commentary on the hunt for Life on Mars.