Shock Vaporization/Devolatilization of Evaporitic Minerals, Halite and Gypsum, in an Open System Investigated by a Two‐Stage Light Gas Gun.

Dry lakebeds might constitute large volatile reservoirs on Mars. Hypervelocity impacts onto ancient dry lakebeds would have affected the volatile distribution on Mars. We developed a new experimental method to investigate the response of evaporitic minerals (halite and gypsum) to impact shocks in an open system. This technique does not result in chemical contamination from the operation of the gas gun. The technique is termed the "two‐valve method," and the gun system is located in the Planetary Exploration Research Center, Chiba Institute of Technology, Japan. We detected the vaporization of halite at 31 GPa and devolatilization from gypsum at 11 GPa, suggesting that impact‐induced volatile release from dry lakebeds has periodically occurred throughout Martian history. The vaporization of halite deposits might have enhanced the production of perchlorates, which are found globally on Mars. The water loss from gypsum possibly explains the coexisting types of Ca‐sulfates found in Gale Crater. Plain Language Summary: We used a new experimental technique to investigate the result of a meteoroid impact into an evaporitic deposit on Mars. Although two‐stage light gas guns are ideal projectile launchers, the dirty gas from the gun has been a long‐standing limitation of this technique that so far greatly complicated analysis of the vapors that are generated due to such impacts. Our new method overcomes this limitation and allows us to measure impact‐generated vapor from evaporitic minerals. We detected NaCl vapor from halite and water vapor from gypsum at velocities lower than the typical impact velocities onto Mars. This suggests that volatile release from ancient dry lakebeds has periodically occurred throughout Martian history, due to stochastic meteoroid impacts. The nature of perchlorates and Ca‐sulfates found on Mars can be interpreted as the result of hypervelocity impacts onto dry lakebeds rich in evaporitic minerals. Key Points: Gas release from halite and gypsum was studied using a two‐stage light gas gun setup that avoids contamination of impact vapors from gun‐related gasesVaporization of halite at 31 GPa and devolatilization (water loss) from gypsum at 11 GPa were detectedImpacts might have resulted in efficient production of perchlorates in Martian soil and produced the anhydrite found in Gale Crater [ABSTRACT FROM AUTHOR]