Martian subsurface volatile concentrations as a function of time: Clues from layered ejecta craters

Martian layered ejecta morphologies are characterized using a new preservation classification system and through measurement of ejecta mobility (EM) ratios. EM, the ratio of ejecta extent to crater radius, is believed to provide information about ejecta material fluidity during emplacement. This study compares EM and preservation classification to determine if subsurface volatile concentrations have changed measurably over time. Results from both regional and local analyses suggest that concentrations of subsurface volatiles have remained approximately constant at the depths and over the time periods recorded by these craters.