As reported in these articles, InSight recorded 174 events until the end of September 2019. Since then, the measurements have continued leading to more than 450 observed marsquakes as of today, which have not yet been analysed in detail. This accounts for one event a day on average. The data allows researchers observing how seismic waves travel through the planet and unveiling its internal characteristics – similar to how x-rays are used in medical tomography. Before InSight landed, researchers had developed a wide range of possible models to represent the internal structure of the red planet. The recorded marsquakes, already after few months, enable refining the understanding of the structure of the planet and to reduce the uncertainties.

Marsquakes are similar to the seismic events we see on Earth, although they are generally of smaller magnitude. The 174 registered marsquakes can be categorized into two families: One includes 24 low-frequency events with magnitudes between 3 and 4, as documented in the papers, with waves propagating through the Martian mantle. A second family of marsquakes comprises 150 events with smaller magnitudes, shallower hypocentral depth and high frequency waves trapped in the Martian crust. “Marsquakes have characteristics already observed on the Moon during the Apollo era, with a long signal duration (10 to 20 minutes) due to the scattering properties of the Martian crust”, explains ETH Professor Giardini. In general, however, he says, interpreting marsquake data is very challenging and in most cases, it is only possible to identify the distance but not the direction from which the waves are arriving.

InSight opens a new era for planetary seismology. The SEIS performance exceeded so far expectations, considering the harsh conditions on Mars, characterized by temperatures ranging from minus 80 to 0 degrees Celsius every day and by strong wind oscillations. Indeed wind shakes the InSight lander and its instrumentation during the day leading to a high level of ambient noise. However, at sunset, the winds calm down allowing recording the quietest seismic data ever collected in the solar system. As a result, most seismic events detected on Mars by SEIS occurred in the quiet night hours. The challenging environment also requires to carefully distinguishing between seismic events and signals originating from movements of the lander, other instruments or atmospheric-induced perturbances.

The hammering by the HP3 instrument (another InSight experiment) and the close passage of whirlwinds (dust devils), recorded by SEIS, allow to map the physical properties of the shallow soil layers just below the station. We now know that SEIS landed on a thin, sandy layer reaching a few meters deep, in the middle of a 20 meter-wide ancient impact crater. At greater depths, the Martian crust has properties comparable to Earth’s crystalline massifs but appears to be more fractured. The propagation of the seismic waves suggest that the upper mantle has a stronger attenuation compared to the lower mantle.

InSight landed in a rather quiet region of Mars, as no events near the station have been recorded up to now. The three biggest events were located in the Cerberus Fossae region about 1’500 km away. It is a tectonic graben system, caused by the weight of the Elysium Mons, the biggest volcano in the Elysium Planitia area. This provides strong evidence that seismic activity on Mars is not only a consequence of the cooling and therewith the shrinking of the planet but also induced by tectonic stress. The total seismic energy released on Mars lies between the one of Earth and of the Moon.

SEIS, complementary to other InSight measurements, also meaningfully contributed data to better understand the meteorological processes on Mars. The instrument’s sensitivity to both wind and atmospheric pressure allowed identifying meteorological phenomena characteristic of Mars, including the many dust devils that pass by the spacecraft every afternoon.

More detailed results of the seismic analysis and additional findings of the InSight mission can be accessed in the series of papers recently published in Nature Geosciences: The seismicity of Mars, Crustal and time-varying magnetic fields at the InSight landing site on Mars, The atmosphere of Mars as observed by InSight, Initial results from the InSight mission on Mars. 

Learn more about the NASA InSight mission: https://mars.nasa.gov/insight/ and about ETH Zurich’s involvement in InSight: www.insight.ethz.ch

Unique in the world

LabQuake exposes rock samples of a maximum size of 7.6 cm to conditions at which deep geothermal energy plants operate: temperatures of up to 170° Celsius and a confining pressure of 170 MPa, which corresponds approximately to 1678 atmospheres or a 17.3 km high water column. The maximum force that the scientists can apply to the rock samples equals to the weight of 125 mid-size SUVs (about 2500 kN).

One of the first applications of LabQuake will be to repeat experiments on rock samples collected in underground research labs. LabQuake ideally supplements experiments at the deca-meter scale performed in the Grimsel In-situ Stimulation and Circulation (ISC) project. Scientists test hypotheses from this project and downscale them to LabQuake. Afterwards, they upscale the new findings and apply them to field scale experiments that are conducted within the Bedretto Laboratory for Geoenergies. Hence, LabQuake bridges the gap between projects at different scales and contributes to improve their accuracy and their performance.

The finances for LabQuake amount to roughly 1.2 million Swiss Francs and were secured through the start-up fund of the Professorship Wiemer, with contributions from the SNF R-equipment programme, the ETH equipment programme and the department of Earth Sciences.

To see how LabQuake was delivered to the SED, watch the time-lapse video here.