Widespread occurrence of (per)chlorate in the Solar System

Abstract

Perchlorate (ClO4−) and chlorate (ClO3−) are ubiquitous on Earth and ClO4− has also been found on Mars. These species can play important roles in geochemical processes such as oxidation of organic matter and as biological electron acceptors, and are also indicators of important photochemical reactions involving oxyanions; on Mars they could be relevant for human habitability both in terms of in situ resource utilization and potential human health effects. For the first time, we extracted, detected and quantified ClO4− and ClO3− in extraterrestrial, non-planetary samples: regolith and rock samples from the Moon, and two chondrite meteorites (Murchison and Fayetteville). Lunar samples were collected by astronauts during the Apollo program, and meteorite samples were recovered immediately after their fall. This fact, together with the heterogeneous distribution of ClO4− and ClO3− within some of the samples, and their relative abundance with respect to other soluble species (e.g., NO3−) are consistent with an extraterrestrial origin of the oxychlorine species. Our results, combined with the previously reported widespread occurrence on Earth and Mars, indicate that ClO4− and ClO3− could be present throughout the Solar System.