In-situ regolith seismic velocity measurement at the InSight landing site on Mars

Brinkman, Nienke; Schmelzbach, Cédric; Sollberger, David; Pierick, Jan ten; Edme, Pascal; Haag, Thomas; Kedar, S.; Hudson, T. L.; Андерссон, Фредрик; Driel, Martin van; Nicollier, Tobias; Robertsson, Johan O. A.; Giardini, Domenico; Spohn, Tilman; Krause, Christian; Grott, M.; Knollenberg, J.; Hurst, Ken Joslin; Rochas, L.; Vallade, Julien; Blandin, Steve; Lognonné, Philippe; Pike, Tom; Banerdt, W. B.

doi:10.1002/essoar.10512064.1

Cited by 5 publications

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References 50 publications

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“… 2020 ; Brinkman et al. 2022 ). Because of the short travel path of around 1.2 m, the traveltimes of the seismic waves were expected to be on the order of several milliseconds only and therefore shorter than the SEIS sampling interval of 10 ms (governed by the sampling frequency of 100 Hz).…”

Section: Soil Mechanical and Thermal Properties Derived From Actions ...mentioning

confidence: 99%

“…Based on these traveltimes, we estimated a bulk P- (compressional) and S- (shear) wave velocity of m/s and m/s, respectively, for the regolith volume between the mole and SEIS (Brinkman et al. 2022 ). Assuming a density of 1200 kg/m 3 , the velocity estimates translate into bulk, shear, and Young’s moduli as well as Poisson’s ratio of MPa, MPa, MPa, and , respectively.…”

Section: Soil Mechanical and Thermal Properties Derived From Actions ...mentioning

confidence: 99%

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The InSight HP3 Penetrator (Mole) on Mars: Soil Properties Derived from the Penetration Attempts and Related Activities

et al. 2022

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The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3–5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5–6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure – as was determined through an extensive, almost two years long campaign – was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign – described in detail in this paper – the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole tip finally reached a depth of about 37 cm, bringing the mole back-end 1–2 cm below the surface. It reversed its downward motion twice during attempts to provide friction through pressure on the regolith instead of directly with the scoop to the mole hull. The penetration record of the mole was used to infer mechanical soil parameters such as the penetration resistance of the duricrust of 0.3–0.7 MPa and a penetration resistance of a deeper layer ($>30~\text{cm}$ > 30 cm depth) of $4.9\pm0.4~\text{MPa}$ 4.9 ± 0.4 MPa . Using the mole’s thermal sensors, thermal conductivity and diffusivity were measured. Applying cone penetration theory, the resistance of the duricrust was used to estimate a cohesion of the latter of 2–15 kPa depending on the internal friction angle of the duricrust. Pushing the scoop with its blade into the surface and chopping off a piece of duricrust provided another estimate of the cohesion of 5.8 kPa. The hammerings of the mole were recorded by the seismometer SEIS and the signals were used to derive P-wave and S-wave velocities representative of the topmost tens of cm of the regolith. Together with the density provided by a thermal conductivity and diffusivity measurement using the mole’s thermal sensors, the elastic moduli were calculated from the seismic velocities. Using empirical correlations from terrestrial soil studies between the shear modulus and cohesion, the previous cohesion estimates were found to be consistent with the elastic moduli. The combined data were used to derive a model of the regolith that has an about 20 cm thick duricrust underneath a 1 cm thick unconsolidated layer of sand mixed with dust and above another 10 cm of unconsolidated sand. Underneath the latter, a layer more resistant to penetration and possibly containing debris from a small impact crater is inferred. The thermal conductivity increases from 14 mW/m K to 34 mW/m K through the 1 cm sand/dust layer, keeps the latter value in the duricrust and the sand layer underneath and then increases to 64 mW/m K in the sand/gravel layer below.

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Section: Soil Mechanical and Thermal Properties Derived From Actions ...mentioning

confidence: 99%

Section: Soil Mechanical and Thermal Properties Derived From Actions ...mentioning

confidence: 99%

The InSight HP3 Penetrator (Mole) on Mars: Soil Properties Derived from the Penetration Attempts and Related Activities

et al. 2022

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“…Therefore, constraining the parameters space is relevant for obtaining the proper model. So far, the best new constraints of the inversion are the shear-wave velocities obtained from the hammering experiment (Lognonné et al, 2020;Brinkman et al, 2022), determined to be lower than 80 m/s at the surface, and the thickness of the shallow regolith layer, expected to be no deeper than 10 m (Golombek et al, 2020b,a). Due to the expected compaction, the S-wave velocity of the first layer is modelled as a power law increase.…”

Section: Inversion Algorithm and Parameterizationmentioning

confidence: 99%

“…This way, the P-wave velocity is derived from the inverted S-wave velocity. In particular, for the shallowest layer, we used Vp/Vs = 1.87, as reported by Brinkman et al (2022), and ρ = 1350 kg/m 3 , following the pre-landing assessment of this site (Morgan et al, 2018). This Vp/Vs lies in the range 1.68 -2.56 for dry unconsolidated material, as shown by investigations on Earth samples and also derived for the Lunar regolith (e.g., Uyanik, 2010;Dal Moro, 2015).…”

Section: Inversion Algorithm and Parameterizationmentioning

confidence: 99%

“…First, the SEIS recordings of the hammering sessions of the HP 3 (Heat Flow and Physical Properties Package) experiment were used to derive the seismic wave velocities in the first tens of centimeters below the ground surface (Brinkman et al, 2019;Lognonné et al, 2020). A re-evaluation of this data has determined the P-wave velocity to be 119 ± 29 m/s and the S-wave velocity to be 61 ± 20 m/s in the first ~40 cm of the shallowest layer (Brinkman et al, 2022). Kenda et al (2020) derived a subsurface model based on ground-motion compliance (the surface response to atmospheric pressure loading) measurements, which was extended by Onodera (2022), who proposed a model with a single discontinuity at ~1 m depth in the first ~75 m of the subsurface below the lander, corresponding to the martian regolith over a layer of coarse blocky material.…”

Section: Introductionmentioning

confidence: 99%

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Empirical H/V spectral ratios at the InSight landing site and implications for the martian subsurface structure

Carrasco

Knapmeyer‐Endrun

Margerin

et al. 2022

Geophysical Journal International

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Summary The H/V spectral ratio inversion is a traditional technique for deriving the local subsurface structure on Earth. We calculated the H/V from the ambient vibrations at different wind levels at the InSight landing site, on Mars, and also computed the H/V from the S-wave coda of the martian seismic events (marsquakes). Different H/V curves were obtained for different wind periods and from the marsquakes. From the ambient vibrations, the recordings during low-wind periods are close to the instrument self-noise level. During high-wind periods, the seismic recordings are highly contaminated by the interaction of the lander with the wind and the martian ground. Therefore, these recordings are less favorable for traditional H/V analysis. Instead, the recordings of the S-wave coda of marsquakes were preferred to derive the characteristic H/V curve of this site between 0.4 and 10 Hz. The final H/V curve presents a characteristic trough at 2.4 Hz and a strong peak at 8 Hz. Using a full diffuse wavefield approach as the forward computation and the Neighbourhood Algorithm as the sampling technique, we invert for the 1D shear-wave velocity structure at the InSight landing site. Based on our inversion results, we propose a strong site effect at the InSight site to be due to the presence of a shallow high-velocity layer (SHVL) over low-velocity units. The SHVL is likely placed below a layer of coarse blocky ejecta and can be associated with Early Amazonian basaltic lava flows. The units below the SHVL have lower velocities, possibly related to a Late Hesperian or Early Amazonian epoch with a different magmatic regime and/or a greater impact rate and more extensive weathering. An extremely weak buried low velocity layer (bLVL) between these lava flows explains the data around the 2.4 Hz trough, whereas a more competent bLVL would not generate this latter feature. These subsurface models are in good agreement with results from hammering experiment and compliance measurements at the InSight landing site. Finally, this site effect is revealed only by seismic events data and explains the larger horizontal than vertical ground-motion recorded for certain type of marsquakes.

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Seasonal Variations of Soil Thermal Conductivity at the InSight Landing Site

Grott

Piqueux

Spohn

et al. 2023

Geophysical Research Letters

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Thermal conductivity is a fundamental physical property that largely controls the range of temperatures experienced at the surface and in the shallow subsurface of a planet. In granular material, heat is transported through grain-to-grain contacts, conduction through the pore-filling gas, and radiation between individual grains. In martian soil, the first two contributions dominate the transport, and grain-to-grain contacts are particularly enhanced if grains are cemented or indurated (Piqueux & Christensen, 2009b;Presley et al., 2009). Conversely, the contribution of heat transport through the gas phase can inform us about the state of soil cementation or induration. Here, the term cementation refers to the deposition of crystalline material and the formation of bridges between grains. In contrast, cohesion is related to an increase in shear strength caused by electrostatic forces. In the following, we will refer to low cohesion granular material as unconsolidated.

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In-situ regolith seismic velocity measurement at the InSight landing site on Mars

Cited by 5 publications

References 50 publications

The InSight HP3 Penetrator (Mole) on Mars: Soil Properties Derived from the Penetration Attempts and Related Activities

The InSight HP3 Penetrator (Mole) on Mars: Soil Properties Derived from the Penetration Attempts and Related Activities

Empirical H/V spectral ratios at the InSight landing site and implications for the martian subsurface structure

Seasonal Variations of Soil Thermal Conductivity at the InSight Landing Site

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