Abstract EANA2026-96

While perchlorate salts rarely occur as natural deposits on Earth, they are thought to be widely distributed on Mars. This has sparked discussion about their toxicity toward putative Martian microorganisms as well as potential future Mars astronauts. Research on perchlorate abundances on Mars and its toxicity has provided new insights, helping to clarify several earlier misconceptions, such as:

1. While 0.4–0.6 wt.% perchlorate has been detected in Martian regolith by the Phoenix lander (more precisely, in the 1:25 regolith-to-solution mixtures, the perchlorate ion concentration ranged from 2.2 to 2.6 mM), these concentrations do not correspond to salt concentrations that might naturally occur on Mars in temporally stable brines formed by deliquescence or brine melting. Concentrations in such brines would be significantly higher, likely reaching saturation levels.
2. While perchlorate is considered an endocrine disruptor in vertebrates (including humans), as it competes with iodide uptake and impairs thyroid hormone synthesis, its toxicity toward microbes is usually caused by its chaotropicity and interactions with biological processes.
3. While perchlorate is thermodynamically a strong oxidant, it is kinetically stabilized in solution, occasionally leading to an overestimation of its potential to function as a direct oxidative stressor in cellular systems.

This presentation will compare perchlorate concentrations occurring on Mars with recently examined microbial perchlorate tolerances. Furthermore, our most recent research on stress responses and cellular perchlorate adaptation mechanisms will be discussed, along with the consequences of using perchlorate-containing regolith for ISRU processes on Mars and the potential risks for astronauts.