Mechanochemical generation of perchlorate on Mars

Perchlorates (ClO₄^-) are widespread in the solar system having been detected on Earth, on Mars, in chondrite meteorites and in lunar samples. On Mars, perchlorates expand the potential for habitable conditions by lowering the freezing point of liquid water in the formation of brines. In future manned space exploration their presence poses a hazard to human health, however, it also represents opportunities as a source of oxygen and fuel. Despite their prevalence, the mechanism(s) of perchlorate formation in different environments are poorly understood. Here, it is demonstrated that perchlorate can be generated through the mechanical activation of silicates in the presence of chloride; a process that is widespread in environments on Mars through aeolian abrasion, and likely other solar system bodies, including Earth. The results of laboratory experiments are reported where a suite of single-phase rock forming minerals, common to the Martian crust, were crushed with halite and the formation of perchlorate measured with ion chromatography. Results indicate that perchlorate generation may have been occurring much more rapidly than previous models have predicted. This provides a potential mechanism for more widespread habitable aqueous niches for life to have existed over the Amazonian on an otherwise largely dry Mars.