  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.
