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NASA’s InSight has detected a large magnitude seismic event, labelled S1222a. The event has a moment magnitude of M(Ma)(W)4.7, with 5 times more seismic moment compared to the second largest even. The event is so large that features are clearly observed that were not seen in any previously detected events. In addition to body phases and Rayleigh waves, we also see Love waves, minor arc surface wave overtones, and multi-orbit surface waves. At long periods, the coda event exceeds 10 hours. The event locates close to the North-South dichotomy and outside the tectonically active Cerberus Fossae region. S1222a does not show any evident geological or tectonic features. The event is extremely rich in frequency content, extending from below 1/30 Hz up to 35 Hz. The event was classified as a broadband type event; we also observe coda decay and polarization similar to that of very high frequency type events., Geophysical Research Letters, 50 (5), ISSN:0094-8276, ISSN:1944-8007

The rate of occurrence of High Frequency (HF) marsquakes, as recorded by InSight at Homestead Hollow, Elysium Planitia, increased after about Ls =33°, and ceased almost completely by Ls =187°, following an apparently seasonal variation with a peak rate near aphelion. We define seismic rate models based on the declination of the Sun, annual solar tides, and the annual CO2 cycle as measured by atmospheric pressure. Evaluation of Akaike weights and evidence ratios shows that the declination of the Sun is the most likely, and the CO2 cycle the least likely driver of this seismic activity, although the discrimination is weak, and the occurrence of a few events in August 2020 is in favor for a triggering by CO2 ice load. We also show that no periodicity related to Phobos' orbit is present in the HF event sequence. Event rate forecasts are presented to allow further discrimination of candidate mechanisms from future observations., Earth and Planetary Science Letters, 576, ISSN:0012-821X, ISSN:1385-013X