Insight Senses its two Biggest Marsquakes so far, Coming From the Opposite Side of the Planet universetoday storybywill
The larger of the two was traced to Valles Marineris, one of Mars’ distinguishing geological features and the largest canyon system in the Solar System. Earlier images of cross-cutting faults and landslides in the region, taken from orbit, suggested that Valles Marineris was seismically active. But this latest event is the first time that seismic activity has been confirmed there. The second, S1000a, occurred 24 days later and was the longest event on record, lasting 94 minutes.
This means that the waves do not reach a seismometer directly but are reflected off the core at least once before reaching the other side of the planet. Savas Ceylan, a co-author from ETH Zürich, explained the significance of these detections in a recent“Recording events within the core shadow zone is a real stepping stone for our understanding of Mars. Prior to these two events, the majority of the seismicity was within about 40 degrees distance of InSight.
While both marsquakes originated on the far side of mars, they also differed in some key respects. In short, S0976a was characterized by only low-frequency energy and was likely much deeper in origin. Meanwhile, S1000a had a very broad frequency spectrum, including low-amplitude Pdiff waves that traversed the core-mantle boundary. This was the first time that InSight detected this kind of seismic energy, which could reveal new insights into Martian seismology.