The prospects for life on Mars: A post Mariner 9 assessment : draft

In this paper, Sagan reflects on the prospect of finding life on Mars in the wake of the Mariner 9 NASA mission. It reviews historical ideas of evidence for life on Mars and offers suggestions for what future missions should look for on the red planet. A later version of this draft was published as "The prospects for life on Mars: A pre-Viking assessment" in the journal Icarus in 1976.