A new experiment conducted by a US-German research team and led Lars Ehm of the University of Stony Brook simulated meteorite impacts in a lab. The findings, published in Earth and Planetary Science Letters, will help scientists reconstruct the conditions present when craters were formed on Earth and other planets.
The scientists observed the changes in the structure of two different minerals of the feldspar group using x-ray diffraction. The results of these experiments show that the same structural changes can occur at very different pressures, depending on the rate of compression.
Meteorite impacts are an essential piece of the puzzle in the formation and evolution of Earth and other planets in our Solar system. However, the conditions of a collision, such as the size of the meteor, its speed, as well as the maximum pressure and temperature developed during a collision, are usually determined long after the collision by the irreversible changes in the state of the rocks of the impact crater.
To solve the problem of restoring collision conditions according to the rocks of the impact crater material, scientists study the behavior of materials at high temperatures and pressures. Minerals of the feldspar group - albite, anorthite and the plagioclase, which is a mixture of the two, are commonly found in the crust of terrestrial planets. Therefore, structural changes in these minerals at high temperatures and pressures can help restore the conditions of ancient collisions.
Researchers studied the amorphization of albite and anorthite minerals under high pressures developed in a diamond anvil cell. The results of the experiments demonstrated that the pressure at which the sample loses its crystal structure and transitions to the amorphous state strongly depends on the rate of increase in load: for example, with a minimum compression rate of 0.1 gigapascals (GPa), albite completely transformed into an amorphous form at a pressure of 31, 5 GPa, while at the highest compression rate of 81 GPa, this transition occurred already at a pressure of 16.5 GPa.
According to the scientists, the current state of the minerals that make up the material of the impact crater will make it possible to simulate the impact conditions of an ancient cosmic collision hundreds to millions of years after the event with more precision.