Abstract

Explosive volcanism should be the most common style on a planet characterized by a low atmospheric pressure and by an assumed high volatile content. However, the observations of the surface of Mars show how explosive volcanism is not widespread as it should be in a planet with the above mentioned characteristics. Therefore, one of the two characteristics should be missing. Considering that the atmospheric pressure has been more or less the same all over the Martian history, then the obvious conclusion is that Mars never had such an high volatile content. Yet, low contents of volatile can still trigger explosive volcanism in the low pressure environment of Mars and this is the reason why several pyroclastic deposits have been observed on the surface of the Red Planet.