Insight Resolves 200 Meters Into the Martian Subsurface for the First Time

An artist’s impression of the layers of impact ejecta, lava, and sediments hidden in the subsurface beneath the InSight lander. Credit: Géraldine Zenhäusern/ETH Zürich.

The NASA InSight lander arrived at Elysium Planitia on Mars in November 2018 with the goal of investigating the structure and composition of the martian interior. Since landing, InSight has been listening for marsquakes and other seismic activity on Mars using its seismometer, SEIS, which converts vibrations from seismic waves into electrical signals. Different types of seismic waves travel at different speeds, which can also be affected by the materials through which they are traveling. In addition to detecting multiple marsquakes, the InSight team has recently identified another seismic signal with an energy peak at a frequency of 2.4 Hz. This peak was identified during periods of low winds, such as those present in the martian summer nights. The team ruled out generation of this peak by the response of the lander to the winds, leading them to conclude that its origin was a natural seismic response of the martian subsurface to interaction of winds with the topography at the landing site.

A study led by Manuel Hobiger of the Swiss Seismological Service and coauthors used this seismic energy peak to investigate the shallow subsurface around the landing site up to a depth of approximately 200 meters (656 feet). This team found that the top 20 meters of the subsurface consist of sandy regolith plus blocky impact ejecta. Beneath these, lava flow layers of 10 meters (upper) and 100 meters (lower) thickness sandwich approximately 45 meters of sedimentary deposits. These results from InSight are consistent with the geological history of this region previously derived from orbital mapping using imaging and spectral data for the surface, which indicate that this region formed through the processes of impact, sedimentation, and volcanic activity over a period of approximately 3.7 billion years. These results will also be useful for predicting the load-bearing capacity and trafficability of the area for future landed missions to Mars. READ MORE