Constraining Martian Regolith and Vortex Parameters From Combined Seismic and Meteorological Measurements

Abstract

The InSight mission (Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport mission; Banerdt et al., 2020) landed on Mars in November 2018 within a quasicircular depression called Homestead hollow (Figure 1; Golombek et al., 2020) in the Elysium Planitia region. Since then, the InSight mission has been performing the first comprehensive surface-based geophysical investigation of Mars using the SEIS (Seismic Experiment for Interior Structure; Lognonné et al., 2019) instrument. This lownoise seismometer with unprecedented sensitivity (Lognonné et al., 2020) contains three long period or very broad band (VBB) sensors and three short period (SP) sensors (Lognonné et al., 2019). To support the seismic measurements InSight also has a high performance barometer, and temperature and wind sensors

Vortex‐Dominated Aeolian Activity at InSight's Landing Site, Part 1: Multi‐Instrument Observations, Analysis, and Implications

“…All data and models are band‐pass filtered in the 0.05–0.3 Hz frequency range. Model parameters indicate a minimum diameter of 5 m at a miss‐distance of 4–5 m from the center of the vortex, Young's modulus of 200 MPa, Poisson's ratio of 0.2 (both values consistent with Lognonné et al., 2020, Murdoch et al., 2020, Kenda et al., 2020, and Garcia et al., 2020 papers), and a core pressure drop of Δ P < 18.5 Pa. The trajectory of the fit is at 130°.…”

“…Given a pair of images in which a track is detected, the time of its formation can only be bounded by the times at which the images were taken. Because multiple candidate vortices can occur within the timeframe of two images, the pressure solution becomes ill‐defined for the identification of the source vortex; the maximum pressure drop in that period does not necessarily indicate the closest encounter due to a size/distance degeneracy (e.g., Lorenz, 2016; Murdoch et al., 2020). This degeneracy arises since the acquired pressure drop of a weak, smaller vortex passing close to the lander cannot be distinguished from a larger, more energetic vortex passing further away, and vice versa.…”

Monitoring of Dust Devil Tracks Around the InSight Landing Site, Mars, and Comparison With In Situ Atmospheric Data

“…Characterization of DDTs is important to better understand seismic, pressure, and wind data signals of passing vortices and to investigate the vortex and ground properties around the InSight lander (Banerdt et al, 2020;Golombek et al, 2020;Murdoch et al, 2020). Future HiRISE images are thus needed to monitor DDTs formation over the summer period around InSight and have a complete overview of atmospheric processes throughout an entire Martian year, in concert with in situ measurements.…”

“…However, for small convective vortices (i.e., diameter <10 m), the DDT's width can actually be a good estimate of their size. Together with information about DDTs' trajectories, they can be used to calculate expected minimum pressure drops and seismic signals in comparison with InSight measurements (Banerdt et al, 2020;Murdoch et al, 2020).…”

“…In particular, a great number of rapid, short-lived pressure drops occurring between late morning and late afternoon (Banfield et al, 2020), which are diagnostic of a vortex passing over or close to the lander and indicate intense convective vortex activity. Seismic signatures corresponding to convective vortices have also been detected by the SEIS instrument (Kenda et al, 2020;Lognonné et al, 2020;Murdoch et al, 2020). Surprisingly, to date, neither of Insight's cameras (the Instrument Context Camera, ICC, and Instrument Deployment Camera, IDC, located respectively below the deck and on the robotic arm of the InSight lander, Maki et al, 2018) have directly imaged any dust devil, unlike previous missions such as Pathfinder (Ferri et al, 2003), Spirit (Greeley et al, 2006), and Curiosity (Lemmon et al, 2017).…”