Near Surface Properties of Martian Regolith Derived From InSight HP<sup>3</sup>‐RAD Temperature Observations During Phobos Transits

Müller, N.; Piqueux, S.; Lemmon, M. T.; Maki, J. N.; Lorenz, Ralph D.; Grott, M.; Spohn, Tilman; Smrekar, S. E.; Knollenberg, J.; Hudson, T. L.; Krause, Christian; Millour, E.; Forget, F.; Golombek, M. P.; Attree, Nicholas; Siegler, M. A.; Banerdt, W. B.

doi:10.1029/2021gl093542

Cited by 14 publications

(7 citation statements)

References 38 publications

(112 reference statements)

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“…Similar estimates for soil thermal conductivity were acquired via RAD observations during Phobos transits across the sun (Mueller et al., 2021) and through near‐surface active heating experiments performed by the HP 3 mole's TEM‐A sensors (Grott et al., 2021; Spohn et al., 2018). Thermal conductivity measurements from HP 3 , from depths ≤37 cm, indicate a low soil thermal conductivity of 0.039 ± 0.001 W m −1 K −1 and a low soil density of ∼1,095 kg m −3 .…”

Section: Review Of Post‐landing In‐situ Constraintsmentioning

confidence: 74%

“…However, the local geology provides critical context for interpreting the results from the instruments. Understanding the local stratigraphy has implications for shallow seismic velocity measurements from SEIS (Kedar et al., 2017; Lognonné et al., 2020; Murdoch et al., 2021), models and observations of seismic signals from nearby crater impacts (Daubar et al., 2020), thermal conductivity and soil porosity estimates from HP 3 (Grott et al., 2021), and thermal inertia and conductivity measurements from the onboard Radiometer (RAD) (Mueller et al., 2021; Piqueux et al., 2021). Multiple pre‐landing and post‐landing geological investigations characterized the landing site by providing geomorphologic observations of local landforms (Golombek et al., 2017, 2018; Golombek, Warner, et al., 2020; Grant et al., 2020; Sweeney et al., 2018; Warner, Golombek, et al., 2017; Warner, Grant, et al., 2020), stratigraphic and sedimentological characteristics of the regolith and lava plains (Grant et al., 2020, 2022; Pan et al., 2020; Warner, Golombek, et al., 2017; Weitz et al., 2020), measurements of the local and regional rock size distributions (Golombek et al., 2017, 2021), observations of active surface processes (e.g., eolian processes) (Baker et al., 2021; Charalambous et al., 2021), and comparisons to other landing sites (Golombek, Kass, et al., 2020; Warner, Schuyler, et al., 2020; Weitz et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

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In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site—A Type Example of a Regolith‐Covered Lava Plain on Mars

et al. 2022

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The InSight lander rests on a regolith-covered, Hesperian to Early Amazonian lava plain in Elysium Planitia within a ∼27-m-diameter, degraded impact crater called Homestead hollow. The km to cm-scale stratigraphy beneath the lander is relevant to the mission's geophysical investigations. Geologic mapping and crater statistics indicate that ∼170 m of mostly Hesperian to Early Amazonian basaltic lavas are underlain by Noachian to Early Hesperian (∼3.6 Ga) materials of possible sedimentary origin. Up to ∼140 m of this volcanic resurfacing occurred in the Early Amazonian at 1.7 Ga, accounting for removal of craters ≤700 m in diameter. Seismic data however, suggest a clastic horizon that interrupts the volcanic sequence between depths of ∼30 and ∼75 m. Meter-scale stratigraphy beneath the lander is constrained by local and regional regolith thickness estimates that indicate up to 10-30 m of coarse-grained, brecciated regolith that fines upwards to a ∼3 m thick loosely-consolidated, sand-dominated unit. The maximum depth of Homestead hollow, at ∼3 m, indicates that the crater is entirely embedded in regolith. The hollow is filled by sand-size eolian sediments, with contributions from sand to cobble-size slope debris, and sand to cobble-size ejecta. Landerbased observations indicate that the fill at Homestead hollow contains a cohesive layer down to ∼10-20 cm depth that is visible in lander rocket-excavated pits and the HP 3 mole hole. The surface of the landing site is capped by a ∼1 to 2 cm-thick loosely granular, sand-sized layer with a microns-thick surficial dust horizon. Plain Language SummaryThe InSight lander has geophysical instruments that are designed to determine the interior structure of Mars. Understanding the results from these instruments requires a geological analysis of materials beneath the landing site at Elysium Planitia. This study presents data that describe the vertical sequence of rocks and soils beneath the lander, as well as the geologic history. The results indicate that InSight rests on a 1.7-billion-year-old lava plain that is covered in a 10-30 m thick regolith that was produced by impact cratering and modified by wind. The uppermost portion of the regolith is a ∼3 m thick horizon of sand. InSight rests on sand within a degraded impact crater. The sandy material contains a slightly cohesive horizon that is only ∼1-2 cm beneath the lander and is up to 10-20 cm thick. The sandy horizon overlies rock fragments that get progressively larger with depth. Bedrock of basaltic lava exists beneath the regolith down to a depth of ∼170 m. The bedrock is interrupted by weaker materials between depths of ∼30 and 75 m. Beneath ∼170 m, the sequence is dominated by ancient (3.7-4.1 billion years old), possibly sedimentary materials.

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Section: Review Of Post‐landing In‐situ Constraintsmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site—A Type Example of a Regolith‐Covered Lava Plain on Mars

et al. 2022

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“…8). HP 3 radiometer measurements of the surface (Mueller et al 2021) yield a thermal inertia dominated by sand and not affected by rocks (Golombek et al 2020a;Piqueux et al 2021;Grott et al 2021). Stereo panoramas enable measurements of rock size and shape that indicate an impact origin for the hollow that was degraded and mostly filled by mass wasting and aeolian activity that transported sand from ejecta into the crater Grant et al 2020Grant et al , 2022Weitz et al 2020).…”

Section: Geology Investigationmentioning

confidence: 99%

Results from InSight Robotic Arm Activities

et al. 2023

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The InSight lander carried an Instrument Deployment System (IDS) that included an Instrument Deployment Arm (IDA), scoop, five finger “claw” grapple, forearm-mounted Instrument Deployment Camera (IDC) requiring arm motion to image a target, and lander-mounted Instrument Context Camera (ICC), designed to image the workspace, and to place the instruments onto the surface. As originally proposed, the IDS included a previously built arm and flight spare black and white cameras and had no science objectives or requirements, or expectation to be used after instrument deployment (90 sols). During project development the detectors were upgraded to color, and it was recognized that the arm could be used to carry out a wide variety of activities that would enable both geology and physical properties investigations. During surface operations for two martian years, the IDA was used during major campaigns to image the surface around the lander, to deploy the instruments, to assist the mole in penetrating beneath the surface, to bury a portion of the seismometer tether, to clean dust from the solar arrays to increase power, and to conduct a surface geology investigation including soil mechanics and physical properties experiments. No other surface mission has engaged in such a sustained and varied campaign of arm and scoop activities directed at such a diverse suite of objectives. Images close to the surface and continuous meteorology measurements provided important constraints on the threshold friction wind speed needed to initiate aeolian saltation and surface creep. The IDA was used extensively for almost 22 months to assist the mole in penetrating into the subsurface. Soil was scraped into piles and dumped onto the seismometer tether six times in an attempt to bury the tether and $\sim30\%$ ∼ 30 % was entrained in the wind and dispersed downwind 1-2 m, darkening the surface. Seven solar array cleaning experiments were conducted by dumping scoops of soil from 35 cm above the lander deck during periods of high wind that dispersed the sand onto the panels that kicked dust off of the panels into suspension in the atmosphere, thereby increasing the power by ∼15% during this period. Final IDA activities included an indentation experiment that used the IDA scoop to push on the ground to measure the plastic deformation of the soil that complemented soil mechanics measurements from scoop interactions with the surface, and two experiments in which SEIS measured the tilt from the arm pressing on the ground to derive near surface elastic properties.

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“…(2019). These are ρ = 1,007 kg m −3 and ρ = 1,211 kg m −3 , where the latter corresponds to an estimate that includes the additional constraint posed by the surface thermal inertia as derived from HP 3 radiometer measurements (N. T. Mueller et al., 2020; N. Mueller et al., 2021). For the soil specific heat capacity, a value of 630 J kg −1 K −1 has been assumed (Morgan et al., 2018).…”

Section: Probe Emplacement Data Acquisition and Inversionmentioning

confidence: 99%

“…As the soil density was not known a priori, we ran two different sets of inversions using the two median densities derived for the InSight landing site by Grott et al (2019). These are ρ = 1,007 kg m −3 and ρ = 1,211 kg m −3 , where the latter corresponds to an estimate that includes the additional constraint posed by the surface thermal inertia as derived from HP 3 radiometer measurements (N. T. Mueller et al, 2020;N. Mueller et al, 2021).…”

Section: Probe Emplacement Data Acquisition and Inversionmentioning

confidence: 99%

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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Near Surface Properties of Martian Regolith Derived From InSight HP³‐RAD Temperature Observations During Phobos Transits

Abstract: The Martian surface temperature response to Phobos transits at the InSight landing site is interpreted• The thermal conductivity or density of the top 0.2 to 4 mm is significantly less than that of the top 4 cm

Cited by 14 publications

References 38 publications

In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site—A Type Example of a Regolith‐Covered Lava Plain on Mars

In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site—A Type Example of a Regolith‐Covered Lava Plain on Mars

Results from InSight Robotic Arm Activities

Seasonal Variations of Soil Thermal Conductivity at the InSight Landing Site

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Near Surface Properties of Martian Regolith Derived From InSight HP3‐RAD Temperature Observations During Phobos Transits

Abstract: The Martian surface temperature response to Phobos transits at the InSight landing site is interpreted• The thermal conductivity or density of the top 0.2 to 4 mm is significantly less than that of the top 4 cm

Cited by 14 publications

References 38 publications

In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site—A Type Example of a Regolith‐Covered Lava Plain on Mars

In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site—A Type Example of a Regolith‐Covered Lava Plain on Mars

Results from InSight Robotic Arm Activities

Seasonal Variations of Soil Thermal Conductivity at the InSight Landing Site

Contact Info

Product

Resources

About

Near Surface Properties of Martian Regolith Derived From InSight HP³‐RAD Temperature Observations During Phobos Transits