Impact-shock behavior of Mg- and Ca-sulfates and their hydrates

Shock recovery experiments on MgSO4, CaSO4, and their hydrates (kieserite, epsomite, and bassanite) were performed to investigate shock-induced dehydration and decomposition at shock pressures up to 36 GPa. The recovered solid samples indicated dehydration at pressures below 24 GPa, but no clear evidence was found for possible decomposition of MgSO4 and CaSO4 to produce MgO or CaO as final products. These sulfates and hydrates have been observed on the surface of Mars, and the present experimental results can be applied towards understanding the presence of surface water on Mars and the recycling of water by impacts. This finding that the sulfate hydrates undergo dehydration upon impact, as well as the fact that the sulfates CaSO4 and MgSO4 absorb moisture, suggests the total amount of water on Mars has remained almost unchanged since the time of formation of the planet.