PENETRATING PYROCLASTICS: IMPLICATIONS FOR MAGMA-WATER INTERACTION ON MARS

The origin of layered sediments on Mars has been attributed to various subaqueous and subaereal processes including volcanic, eolian, fluvial, lacustrine and marine. Here we present a geophysical technique used on Earth that could provide decisive evidence for original depositional processes on Mars and contribute to our understanding of past environments on the red planet, particularly subaqueous and volcanic ones. Ground Penetrating Radar (GPR) images of a pyroclastic flow deposit triggered by explosive magma-water interaction during a caldera-forming eruption in New Zealand, reveal low angle dune structures with wavelengths up to 45 meters. GPR reflectors correlate with long telescoping lee-side bedforms and migrating dune crests, providing otherwise concealed flow direction and source vent location information, as well as insight into mechanisms for wave-generated currents. The porous nature of the unconsolidated pumice and ash, and the systematic variation of grainsizes that define the internal dune stratification are ideal conditions for a GPR study, and could theoretically be repeated on Mars where conditions are known to be similar.