NASA reports that, Mars Insight lander has detected a faint seismic signal through its SEIS (Seismic Experiment for Interior Structure) instrument. This is the first time in 128 sols that the lander had recorded trembling from inside the planet. All the earlier recorded events were of the surface activities like the wind.
In the below video and audio illustration, three distinct kinds of sounds can be heard – which differentiates between the noise from the wind prevalent in the martian surface, the seismic event itself and the tiny noise made by the robotic arm as it moves around taking pictures. Based on this comparison, NASA scientists think that it could likely be the first recorded Marsquake as the surface is usually extremely quiet.
The detailed press release by NASA can be found here.