Small-scale Structure of the Martian Mantle

The InSight mission's SEIS instrument has provided a unique opportunity to probe the deep interior of Mars. This seismic exploration of the Martian interior has emerged as a promising avenue for revealing the enigmatic geophysical properties and dynamic processes within the planet's mantle.In this study, we present an analysis of the seismic signature of marsquakes which transit deep into the mantle, providing crucial information on the seismic velocity profile and potential heterogeneities. The quakes show a characteristic late emergence of the first energy at higher frequencies which can be analysed as due to the scattering of seismic energy as it transits the mantle. From this we are able to quantify the size distribution of the mantle's small-scale heterogeneity as well as to constrain the rheological properties and convective vigor of the Martian mantle.As unlike Earth, Mars has sealed its mantle contents under a stagnant lid, we use our observations to provide evidence about the early stages of planetary formation and differentiation on Mars. Our findings contribute to the better understanding of the Martian mantle's geodynamics and allow a comparative assessment of the evolution of planetary interiors that likely apply to other planets that lack plate tectonics.