Seismology on Mars: An analysis of direct, reflected, and converted seismic body waves with implications for interior structure

The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission has been collecting high-quality seismic data on Mars since early 2019 that provide the first direct observations of its interior structure. Here we report a complete analysis part marsquakes known as low-frequency events (main energy below 1 Hz) are sensitive to deep interior. To identify body-wave arrivals in highly-scattered martian seismograms, employ four complementary approaches: 1) time-domain envelopes; 2) polarised waveforms their 3) polarisation analysis; 4) waveform matching. Through careful application this processing scheme each marsquake, able significantly increase number phase picks relative earlier analyses (from 41 76), including from (P S), reflected (PP, SS, PPP, SSS, ScS), converted (Ps Sp) phases. constrain depth marsquakes, also phases (pP sS). Following this, invert an initial set for models structure, event distance, depth, while predicting travel times not identified at outset. Based predictions, repick (every pick is subject our scheme), thereby enlarging differential travel-time (all main P-wave arrival), subsequently re-invert updated structure models, distances, depths. Proceeding thus, present radial velocity crust, mantle, core. We observe crustal interfaces average depths 10, 25, 45 km, respectively, which former two interpreted intra-crustal latter crust-mantle boundary. find upper mantle consistent with low-velocity zone associated thermal lithosphere gradient range 2.4–2.9 K/km extends ~450 km. Martian indicates potential core-mantle-boundary temperatures ranges 1650–1750 K 1900–2100 K, implying entirely liquid core present. identification ScS phases, obtain improved estimate radius (1820–1870 km) mean density (6–6.2 g/cm3).