Fixation of atmospheric nitrogen on present-day Mars during dust events

Abstract

N2 is the second most abundant gas in the present-day Martian atmosphere and hosts the essential biochemical element N. Nitrate and (per)chlorate have been detected in numerous aeolian sediments in Gale crater. Thus, a potential nitrogen fixation may be active on present-day Mars. Interactions between Martian atmosphere and surface during dust events can trigger electrostatic discharge (ESD) and complex electrochemical reactions. By simulating this process in a Mars chamber, nitrate and (per)chlorate were produced under present-day Martian atmospheric conditions. Notably, the obtained nitrate/(per)chlorate abundance ratio is in agreement with Gale crater observations (< 1.0), but much lower than those in terrestrial Mars analogues and the products of other pathways proposed for Mars. The results strongly indicate that electrochemical reactions during Mars dust events represents a new nitrogen fixation mechanism on present-day Mars. It is different from other fixation processes on Earth and early Mars, expanding the knowledge of nitrogen cycle and nitrogen fixation in solar system. Electrochemical reactions may also play crucial roles in global nitrogen cycling throughout the Amazonian period. These nitrate salts in Martian dusts potentially provide an accessible source of nitrogen for possible organic molecule formation on present-day Mars.