Seismic investigations of the Martian near-surface at the InSight landing site
- 1ETH Zurich, Institute of Geophysics, D-ERDW, Zurich, Switzerland (cedric.schmelzbach@erdw.ethz.ch)
- 2Jet Propulsion Laboratory, California Institute of Technology, USA
- 3Deutsches Zentrum für Luft und Raumfahrt, Germany
- 4Institut de Physique du Globe de Paris, France
- 5Institut Supérieur de l'Aéronautique et de l'Espace (ISAE), France
- 6Imperial College, London, UK
- *A full list of authors appears at the end of the abstract
The InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet. A second surface-based instrument, the heat flow and physical properties package HP3, was placed on the Martian ground about 1.1 m away from SEIS. HP3 includes a self-hammering probe called the ‘mole’ to measure the heat coming from Mars' interior at shallow depth to reveal the planet's thermal history. While SEIS was designed to study the deep structure of Mars, seismic signals such as the hammering ‘noise’ as well as ambient and other instrument-generated vibrations allow us to investigate the shallow subsurface. The resultant near-surface elastic property models provide additional information to interpret the SEIS data and allow extracting unique geotechnical information on the Martian regolith.
The seismic signals recorded during HP3 mole operations provide information about the mole attitude and health as well as shed light on the near-surface, despite the fact that the HP3 mole continues to have difficulty penetrating below 40 cm (one mole length). The seismic investigation of the HP3 hammering signals, however, was not originally planned during mission design and hence faced several technical challenges. For example, the anti-aliasing filters of the seismic-data acquisition chain were adapted when recording the mole hammering to allow recovering information above the nominal Nyquist frequency. In addition, the independently operating SEIS, HP3 and lander clocks had to be correlated more frequently than in normal operation to enable high-precision timing.
To date, the analysis of the hammering signals allowed us to constrain the bulk P-wave velocity of the volume between the mole tip and SEIS (top 30 cm) to around 120 m/s. This low velocity value is compatible with laboratory tests performed on Martian regolith analogs with a density of around 1500 kg/m3. Furthermore, the SEIS leveling system resonances, seismic recordings of atmospheric pressure signals, HP3 housekeeping data, and imagery provide additional constraints to establish a first seismic model of the shallow (topmost meters) subsurface at the landing site.
Cedric Schmelzbach, Nienke Brinkman, David Sollberger, Sharon Kedar, Matthias Grott, Fredrik Andersson, Johan Robertsson, Martin van Driel, Simon Stähler, Jan ten Pierick, Troy L. Hudson, Kenneth Hurst, Melanie Drilleau, Balthasar Kenda, Raphael Garcia, Naomi Murdoch, Domenico Giardini, Philippe Lognonné, W. Tom Pike, Tilman Spohn, W. Bruce Banerdt, Lucile Fayon, Anna Horleston, Aaron Kiely, Brigitte Knapmeyer-Endrun, Christian Krause, Nicholas C. Schmerr, Pierre Delage, Nick Teanby, Christos Vrettos
How to cite: Schmelzbach, C., Brinkman, N., Sollberger, D., Kedar, S., Grott, M., Andersson, F., Robertsson, J., van Driel, M., Stähler, S., ten Pierick, J., Hudson, T., Hurst, K., Drilleau, M., Kenda, B., Garcia, R., Murdoch, N., Giardini, D., Lognonne, P., Pike, W. T., and Spohn, T. and the InSight SEIS and Near Surface Team: Seismic investigations of the Martian near-surface at the InSight landing site, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20481, https://doi.org/10.5194/egusphere-egu2020-20481, 2020.
