Imaging Mars: Seeking Characteristic Signals in Models of the Martian Interior

Abstract:

We expect that the interiors of terrestrial planets look somewhat like our own - with a crust, a mantle hosting a range of mineralogical transformations and an iron alloy core. Data from existing geophysical observations of Mars, including its moment of inertia and mass, together with mineralogical, cosmochemical, geodynamical and meteorite information and modeling have lead to the creation of a variety of models of the density profile of the martian interior. A number of these density models are accompanied by seismic profiles in the planet. The presence of liquid layer in the outer core is supported by geodetic information; the presence of a solid inner core has not been conclusively ruled out by previous studies though it is unlikely. Some models predict jumps in seismic velocity in the mantle as steadily increasing pressure changes the stable phase assemblage, while other models instead show smooth increases in velocity. Attenuation in the martian mantle has been estimated by considering the tidal dissipation observed as Phobos orbits Mars. 

We investigate a range of models of Mars' density and velocity structure, using both simulations of Mars' normal mode oscillations and calculations of body wave travel times, ray paths and synthetic waveforms. For several features of the martian interior, from the presence of sharp boundaries in the mantle, to probable core sizes, we seek seismically observable signatures. Probing Mars' interior using seismic techniques is a key aim of the upcoming InSight mission to Mars; if seismic sources are sufficiently numerous and energetic then the presence of known seismic signatures for characteristics of the martian interior will help us to understand what lies beneath the surface of Mars.