Chlorine speciation reveals the occurrence of perchlorate in deserts on Earth and implications for Mars

Abstract:

The formation and preservation of perchlorate (ClO₄^-) in deserts on Earth is of growing interest, since the desert could serve as a viable analog for the Martian landscape where has a great perchlorate content. In this study, we investigated perchlorate distribution and chlorine (Cl) speciation in samples collected from the Taklimakan desert of China and Atacama desert of Chile by IC-MS/MS and Cl K-edge μ-XANES analyses. Results showed that that moraine contains a higher perchlorate concentration and the ClO₄^-/Cl^- ratio in comparison with other types of samples from the Taklimakan desert, which may be explained by the reason that the loss of perchlorate in glacial debris is relatively lower. The μ-XRF-XANES analysis indicated that the distribution of perchlorate is quite heterogeneous and that KClO₄ could be the dominant perchlorate species in the desert samples. This observation appears to be different from the dominant perchlorate species (e.g., Mg(ClO₄)₂) on Martial soils, likely suggesting different formation mechanisms of perchlorate and preserved environments in the history and present-day on Earth and Mars.