Nitrate, perchlorate, and iodate co-occur in coastal and inland deserts on Earth

• Perchlorate, nitrate, and iodate abundances were quantified in four deserts.
• Perchlorate and iodate concentrations were highest in the Atacama Desert.
• Our work supports a localized, unknown source of perchlorate in the Atacama Desert.
• Salt abundance varies by degree of landscape stability, geologic age, and climate.
• We examine controls on salt preservation and the role of deserts as Martian analogs.

Deserts accumulate soluble salts from atmospheric deposition that impact human health, are a source of nutrients for organisms, and provide insight into how landscapes evolved on Earth and Mars. We quantified perchlorate, nitrate, and iodate abundances and co-occurrence in terrestrial deserts to identify fundamental controls on soluble salt deposition and post-depositional cycling. Soils and nitrate deposits were examined in Death Valley, USA; Atacama Desert, Chile; Kumtag Desert, China; and along an environmental gradient in the Transantarctic Mountains, Antarctica. Concentrations of soluble salts were highest in the Transantarctic Mountains and Atacama Desert, where stable, hyper-arid landscapes accumulate atmospheric salts over million-year time scales. Average nitrate concentrations of 61.3 g kg− 1 in the Transantarctic Mountains and 53.0 g kg− 1 in the Atacama Desert were significantly greater than respective averages of 8.60 g kg− 1 and 5.14 g kg− 1 in Kumtag Desert and Death Valley. Perchlorate and iodate concentrations in the Atacama Desert averaged 206 mg kg− 1 and 344 mg kg− 1, respectively, which were two to three orders of magnitude greater than in Antarctica and other sites. Our findings suggest that local processes in the Atacama Desert result either in higher rates of perchlorate and iodate deposition, or a greater preservation of these salts relative to nitrate when compared to Antarctic landscapes. Lower salt concentrations in the Death Valley and Kumtag Desert deposits likely result from relatively wet present-day and paleoclimatic conditions, a more active geologic history, and a greater likelihood that biocycling disrupted long-term salt accumulation. Associations of perchlorate and nitrate were significantly higher than iodate-nitrate and iodate-perchlorate correlations in the four deserts. Perchlorate-nitrate relationships ranged from insignificant to highly significant with stronger correlations in the Atacama Desert and Kumtag Desert compared to the Transantarctic Mountains and Death Valley. Weaker geochemical associations with iodate were attributed to differences in local deposition rates or post-depositional cycling. Interestingly, relationships among perchlorate, nitrate, and iodate were generally stronger when examined by site within each desert compared to analyzing the soils for each desert as a whole, suggesting more localized controls on soluble salt preservation. We conclude that soluble salts vary in concentration and type across Earth's deserts as a result of present-day environment, paleoclimate conditions, biocycling, and geologic age.