Perchlorates on Mars: Occurrence and implications for putative life on the Red Planet

The discovery of perchlorate in martian regolith, ubiquitously distributed at levels far exceeding those noted on Earth, raises challenges for in situ resource utilization and life-supporting systems. However, this challenge can be overcome by organisms with extreme tolerance to various stressors, characterization of the mechanisms supporting such features, and their subsequent employment in biological systems using genetic engineering and synthetic biology. Using such organisms could be an excellent complement to the physical and chemical technologies of perchlorate removal. Here, we review the research devoted to perchlorates on Mars, their types, spatial variability, age, and production mechanisms. We also characterize the perchlorate toxicity and the organisms (photosynthetic and chemoautotrophic bacteria as well as heterotrophic microorganisms and microinvertebrates) evidenced to withstand exposure to high perchlorate concentrations. The mechanisms behind this tolerance are also discussed in the context of future research prospects and their use in Mars exploration.