The SEIS (Seismic Experiment for Interior Structure) instrument on NASA’s InSight lander detected the faint seismic signal on April 6, 2019, the lander’s 128th Martian day (sol). An artist’s impression of the InSight lander on Mars. Image credit: NASA / JPL-Caltech. Most people are familiar with quakes on Earth, which occur on faults created by the motion of tectonic plates. Mars and the Moon do not have tectonic plates, but they still experience...