Abstract
Clues to a planet's geologic history are contained in its interior structure, particularly its core. We detected reflections of seismic waves from the core-mantle boundary of Mars using InSight seismic data and inverted these together with geodetic data to constrain the radius of the liquid metal core to 1830 ± 40 kilometers. The large core implies a martian mantle mineralogically similar to the terrestrial upper mantle and transition zone but differing from Earth by not having a bridgmanite-dominated lower mantle. We inferred a mean core density of 5.7 to 6.3 grams per cubic centimeter, which requires a substantial complement of light elements dissolved in the iron-nickel core. The seismic core shadow as seen from InSight's location covers half the surface of Mars, including the majority of potentially active regions-e.g., Tharsis-possibly limiting the number of detectable marsquakes.
Highlights
The core of a planet plays a prominent role because it governs many of the fundamental processes from dynamo action and magnetic field generation to mantle convection that impact the surface through volcanic and tectonic activity, and may influence the early climate through magnetic shielding of the atmosphere
In the analysis described we conduct frequency-dependent polarization analysis (FDPA) on waveforms recorded by InSight SEIS VBB to identify the arrival of bodywave phases
(2) Within the ScS prediction time window, we identify peaks with a horizontally rectilinear motion (HRM) maximum and simultaneous vertically rectilinear motion (VRM) minimum where (a) HRM/VRM > 1 and (b) HRMmax>HRMmean +σHRM and (c) VRMmin
Summary
The core of a planet plays a prominent role because it governs many of the fundamental processes from dynamo action and magnetic field generation to mantle convection that impact the surface through volcanic and tectonic activity, and may influence the early climate through magnetic shielding of the atmosphere. To identify energy pulses that are consistent with ScS, we performed a slant stack [37] for the events, using predicted travel times in 5000 mantle models compatible with surface reflected seismic body waves [32]. The spectral character and the travel time of the direct S-wave for the most distant event (S0167b) located to date [30, 32] was consistent with and comparable to that of the ScS phase (Fig. S6-1) [38] This supports the identification of the latter as a core-reflection that has traversed the entire attenuating mantle. The new Martian seismic data and models presented here provide a wealth of new insights into the interior structure of Mars, which contain the clues needed to unravel the planetary building blocks [57], the physical and chemical conditions during assembly [52] and chronology of crust, mantle, and core formation [25]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
