Shock-Chemistry in Natural Materials and Evolution of Planetary Surfaces

摘要

There are two possible types of chemical reactions that can take place due to shock-loading of a mineral. The first type is one that takes place on a longer time scale than the shock event, and is due to ''shock activation'' of the mineral, i.e., the increase in specific free energy due to increased densities of defects and dislocations. An example of this type was experimentally studied by measuring shock-enhanced dissolution rates of three silicate minerals. The second type is the reaction that occurs immediately, or upon release to ambient pressure, and is due to the large increase in internal energy provided by the shock, together with the shift in chemical equilibrium brought about by the increased pressure and temperature. The clay mineral nontronite was the subject of an experimental study of such reactions. Both processes can affect planetary surfaces, either independently or together. The two processes, acting in synergy, are invoked to explain the composition, mineralogy, color, and physical properties of the Martian soil. (ERA citation 12:046381)