© Horelston et al. (2022) TSRMars surface relief map showing InSight’s location (orange triangle), other located marsquakes (purple dots) that cluster around 30° distance, close to Cerberus Fossae, and S0976a, located within Valles Marineris just north of Sollis Planum. S1000a’s location is predicted to be somewhere within the shaded region between 107° and 147° from InSight.
Seismic wave data from the events could help researchers learn more about the interior layers of Mars, particularly its core-mantle boundary, researchers from InSight's Marsquake Service (MQS) report in The Seismic Record.
Anna Horleston of the University of Bristol and colleagues were able to identify reflected PP and SS waves from the magnitude 4.2 event, called S0976a, and locate its origin in the Valles Marineris, a massive canyon network that is one of Mars' most distinguishing geological features and one of the largest graben systems in the Solar System. Earlier orbital images of cross-cutting faults and landslides suggested the area would be seismically active, but the new event is the first confirmed seismic activity there.
S1000a, the magnitude 4.1 event recorded 24 days later, was characterized by reflected PP and SS waves as well as Pdiff waves, small amplitude waves that have traversed the core-mantle boundary. This is the first time Pdiff waves have been spotted by the InSight mission. The researchers could not definitively pinpoint S1000a's location, but like S0976a it originated on Mars' far side. The seismic energy from S1000a also holds the distinction of being the longest recorded on Mars, lasting 94 minutes.
Comment: A day earlier the same area was hit by 6.1 magnitude quake.