On 19 December 2018, the NASA InSight mission placed a seismometer on the surface of Mars. It aims to record marsquakes in order to to gain a better understanding of the planet’s interior. Since the very first day, the data recorded is continuously scrutinized by the Marsquake Service led by ETH Zurich, operated by the Seismology and Geodynamics group and the Swiss Seismological Service. At first, the data mostly showed the frequency and intensity of dust devils, whirlwinds which are very common on Mars. This already proved that the seismometer was performing well. On 6 April 2019 (Sol 128, 15:32 local Mars time), researchers from ETH on duty for the Marsquake Service discovered a potential marsquake in the data. It is the first signal that appears to have come from inside Mars, even though its exact cause is still an on-going scientific investigation.
Three other signals of likely seismic origin occurred on 14 March, 10 April, and 11 April 2019. These signals are more ambiguous to the InSight team than the one on 6 April, but do not appear to be clearly associated with atmospheric disturbances or other known noise sources. They are smaller than the event on 6 April and were only detected by the more sensitive broadband sensors. The team will continue to study these events to try to determine their origin.
Based on these first records, marsquakes seem to be distinct to earthquakes. According to their size and long duration, they are more similar to quakes recorded on the Moon by the Apollo programme. Whereas on Earth plate tectonics is the dominant process that provokes quakes, on the Moon the cooling and contraction causes tremors. The relevant processes at Mars are not yet fully understood. In any case, stress is built up over time until it is strong enough to break the crust. Different materials can change the speed of seismic waves or reflect them, allowing scientists to use these waves to learn about the interior of a planet and model its formation. The events recorded until now are too small to provide useful data on the deep Martian interior. Nevertheless, they mark a milestone of the InSight mission, proving the efficiency of the data processing and analysis capabilities, both developed at ETH Zurich.