VTechWorks staff will be away for the Thanksgiving holiday beginning at noon on Wednesday, November 27, through Friday, November 29. We will resume normal operations on Monday, December 2. Thank you for your patience.

Browsing by Author "Banerdt, W. B."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Machine learning and marsquakes: a tool to predict atmospheric-seismic noise for the NASA InSight mission
    Stott, A. E.; Garcia, R. F.; Chedozeau, A.; Spiga, A.; Murdoch, N.; Pinot, B.; Mimoun, D.; Charalambous, C.; Horleston, A.; King, Scott D.; Kawamura, T.; Dahmen, N.; Barkaoui, S.; Lognonne, P.; Banerdt, W. B. (Oxford University Press, 2023-01-04)
    The SEIS (seismic experiment for the interior structure of Mars) experiment on the NASA InSight mission has catalogued hundreds of marsquakes so far. However, the detectability of these events is controlled by the weather which generates noise on the seismometer. This affects the catalogue on both diurnal and seasonal scales. We propose to use machine learning methods to fit the wind, pressure and temperature data to the seismic energy recorded in the 0.4–1 and 2.2–2.6 Hz bandwidths to examine low- (LF) and high-frequency (HF) seismic event categories respectively. We implement Gaussian process regression and neural network models for this task. This approach provides the relationship between the atmospheric state and seismic energy. The obtained seismic energy estimate is used to calculate signal-to-noise ratios (SNR) of marsquakes for multiple bandwidths. We can then demonstrate the presence of LF energy above the noise level during several events predominantly categorized as HF, suggesting a continuum in event spectra distribution across the marsquake types. We introduce an algorithm to detect marsquakes based on the subtraction of the predicted noise from the observed data. This algorithm finds 39 previously undetected marsquakes, with another 40 possible candidates. Furthermore, an analysis of the detection algorithm’s variable threshold provides an empirical estimate of marsquake detectivity. This suggests that events producing the largest signal on the seismometer would be seen almost all the time, the median size signal event 45–50 per cent of the time and smallest signal events 5−20 per cent of the time.
  • Thumbnail Image
    Seasonal Variations of Soil Thermal Conductivity at the InSight Landing Site
    Grott, M.; Piqueux, S.; Spohn, T.; Knollenberg, J.; Krause, C.; Marteau, E.; Hudson, T. L.; Forget, F.; Lange, L.; Mueller, N.; Golombek, M.; Nagihara, S.; Morgan, P.; Murphy, J. P.; Siegler, M.; King, Scott D.; Banfield, D.; Smrekar, S. E.; Banerdt, W. B. (American Geophysical Union, 2023-04)
    The heat flow and physical properties package measured soil thermal conductivity at the landing site in the 0.03-0.37 m depth range. Six measurements spanning solar longitudes from 8.0 degrees to 210.0 degrees were made and atmospheric pressure at the site was simultaneously measured using InSight's Pressure Sensor. We find that soil thermal conductivity strongly correlates with atmospheric pressure. This trend is compatible with predictions of the pressure dependence of thermal conductivity for unconsolidated soils under martian atmospheric conditions, indicating that heat transport through the pore filling gas is a major contributor to the total heat transport. Therefore, any cementation or induration of the soil sampled by the experiments must be minimal and soil surrounding the mole at depths below the duricrust is likely unconsolidated. Thermal conductivity data presented here are the first direct evidence that the atmosphere interacts with the top most meter of material on Mars.
  • Thumbnail Image
    Surface waves and crustal structure on Mars
    Kim, D.; Banerdt, W. B.; Ceylan, S.; Giardini, D.; Lekic, V.; Lognonne, P.; Beghein, C.; Beucler, E.; Carrasco, S.; Charalambous, C.; Clinton, J.; Drilleau, M.; Duran, C.; Golombek, M.; Joshi, R.; Khan, A.; Knapmeyer-Endrun, B.; Li, J.; Maguire, Ross; Pike, W. T.; Samuel, H.; Schimmel, M.; Schmerr, N. C.; Stahler, S. C.; Stutzmann, E.; Wieczorek, M.; Xu, Z.; Batov, A.; Bozdag, E.; Dahmen, N.; Davis, P.; Gudkova, T.; Horleston, A.; Huang, Q.; Kawamura, T.; King, Scott D.; McLennan, S. M.; Nimmo, F.; Plasman, M.; Plesa, A. C.; Stepanova, I. E.; Weidner, E.; Zenhausern, G.; Daubar, I. J.; Fernando, B.; Garcia, R. F.; Posiolova, L.; Panning, M. P. (AAAS, 2022-10-28)
    We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.
  • Thumbnail Image
    Thermal Conductivity of the Martian Soil at the InSight Landing Site From HP3 Active Heating Experiments
    Grott, M.; Spohn, T.; Knollenberg, J.; Krause, C.; Hudson, T. L.; Piqueux, S.; Mueller, N.; Golombek, M.; Vrettos, C.; Marteau, E.; Nagihara, S.; Morgan, P.; Murphy, J. P.; Siegler, M.; King, Scott D.; Smrekar, S. E.; Banerdt, W. B. (American Geophysical Union, 2021-07-14)
    The heat flow and physical properties package (HP3) of the InSight Mars mission is an instrument package designed to determine the martian planetary heat flow. To this end, the package was designed to emplace sensors into the martian subsurface and measure the thermal conductivity as well as the geothermal gradient in the 0–5 m depth range. After emplacing the probe to a tip depth of 0.37 m, a first reliable measurement of the average soil thermal conductivity in the 0.03–0.37 m depth range was performed. Using the HP3 mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 ± 0.002 W m−1 K−1, consistent with the results of orbital and in-situ thermal inertia estimates. This low thermal conductivity implies that 85%–95% of all particles are smaller than 104–173 μm and suggests that soil cementation is minimal, contrary to the considerable degree of cementation suggested by image data. Rather, cementing agents like salts could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are (Formula presented.) kg m−3, indicating soil porosities of (Formula presented.) %.