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Thermal Conductivity of the Martian Soil at the InSight Landing site from HP$^{3}$ Active Heating Experiments
  • +14
  • Matthias Grott,
  • T. Spohn,
  • Joerg Knollenberg,
  • Christian Krause,
  • Troy L. Hudson,
  • Sylvain Piqueux,
  • N. Müller,
  • Matthew P. Golombek,
  • Christos Vrettos,
  • Eloise Marteau,
  • Seiichi Nagihara,
  • Paul Morgan,
  • J.P. Murphy,
  • Matthew Adam Siegler,
  • Scott D. King,
  • Suzanne E Smrekar,
  • William Bruce Banerdt
Matthias Grott
DLR Institute for Planetary Research

Corresponding Author:[email protected]

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T. Spohn
International Space Science Institute (ISSI)
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Joerg Knollenberg
DLR Institute for Planetary Research
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Christian Krause
DLR Institute of Space Systems
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Troy L. Hudson
Jet Propulsion Laboratory
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Sylvain Piqueux
Jet Propulsion Laboratory
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N. Müller
German Aerospace Center (DLR), Institute of Planetary Research
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Matthew P. Golombek
California Institute of Technology/JPL
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Christos Vrettos
Technical University of Kaiserslautern
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Eloise Marteau
Jet Propulsion Laboratory
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Seiichi Nagihara
Texas Tech University
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Paul Morgan
Colorado School of Mines
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J.P. Murphy
Virginia Polytechnic Institute and State University
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Matthew Adam Siegler
Planetary Sciences Institute
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Scott D. King
Virginia Tech
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Suzanne E Smrekar
Jet Propulsion Laboratory
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William Bruce Banerdt
Jet Propulsion Lab (NASA)
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Abstract

The heat flow and physical properties package (HP$^3$) 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 to 0.37 m depth range was performed. Using the HP$^3$ mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 $\pm$ 0.002 W m$^{-1}$ K$^{-1}$, consistent with the results of orbital and in-situ thermal inertia measurements. This low thermal conductivity implies that 85 to 95\% of all particles are smaller than 104-173 $\mu$m and suggests that any cement contributing to soil cohesion cannot significantly increase grain-to-grain contact areas by forming cementing necks, but could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are 1211$_{-113}^{+149}$ kg m$^{-3}$, indicating soil porosities of 61 \%.
Jul 2021Published in Journal of Geophysical Research: Planets volume 126 issue 7. 10.1029/2021JE006861