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Resonances and Lander Modes Observed by Insight on Mars (1-9 Hz)

Session: Insight Seismology on Mars: Results From the First Martian Year of Data and Prospects for the Future

Type: Oral

Date: 4/23/2021

Presentation Time: 02:45 PM Pacific

Description: 

NASA's InSight lander successfully touched down on Mars in November 2018 and has continuous recordings from its seismometer since February 2019. The seismic recordings reveal diurnal and seasonal changes of the broad band noise level, which are consistent with variations of the local atmospheric conditions.

The seismic data include a variety of spectral peaks, which are interpreted as wind-excited mechanical resonances of the lander, resonances of the subsurface, or artifacts produced in the measurement system. Understanding the origin of these signals is critical for the detection and characterization of marsquakes.

We identify the major spectral peaks between 1 and 9 Hz, corresponding to the frequency range most relevant to observed marsquake events. We track the variations in frequency, amplitude, and polarization of these peaks over the duration of the mission until Sol 650. The majority of these peaks can readily be classified as measurement artifacts or lander resonances. We find that some temporary peaks correlate well with movements of the robotic arm. Of particular interest is the prominent resonance at 2.4 Hz, which is used to discriminate between seismic events and local noise. In contrast to the lander modes, the 2.4 Hz resonance has distinctly different features: 1) a broad and stable spectral shape, slightly shifted on each component; 2) predominantly vertical energy/polarization; 3) temperature-independent peak frequency; 4) weak or no amplification by local winds, though there is a slow change in the diurnal and seasonal amplitude; 5) excitation during all seismic events that excite this frequency band.

Based on these observations, we suggest that the 2.4 Hz resonance is the only mode that could be related to a local ground structure.

Presenting Author: Géraldine Zenhäusern

Student Presenter: Yes

Authors