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Near surface properties derived from Phobos transits with HP RAD³ on InSight, Mars
  • +15
  • Nils T Mueller,
  • Sylvain Piqueux,
  • Mark T Lemmon,
  • Justin N. Maki,
  • Ralph D. Lorenz,
  • Matthias Grott,
  • Tilman Spohn,
  • Suzanne E. Smrekar,
  • Joerg Knollenberg,
  • Troy L. Hudson,
  • Christian Krause,
  • Ehouarn Millour,
  • Forget Francois,
  • Matthew P. Golombek,
  • Axel Hagermann,
  • Nicholas Attree,
  • Matthew Adam Siegler,
  • William Bruce Banerdt
Nils T Mueller
German Aerospace Center (DLR), Institute of Planetary Research

Corresponding Author:[email protected]

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Sylvain Piqueux
Jet Propulsion Laboratory
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Mark T Lemmon
Space Science Institute
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Justin N. Maki
Jet Propulsion Laboratory, California Institute of Technology
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Ralph D. Lorenz
Johns Hopkins University Applied Physics Lab
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Matthias Grott
DLR Institute for Planetary Research
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Tilman Spohn
Institute of Planetary Research
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Suzanne E. Smrekar
Jet Propulsion Laboratory
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Joerg Knollenberg
DLR Institute for Planetary Research
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Troy L. Hudson
Jet Propulsion Laboratory
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Christian Krause
DLR Institute of Space Systems
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Ehouarn Millour
Laboratoire de Meteorologie Dynamique
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Forget Francois
LMD
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Matthew P. Golombek
California Institute of Technology/JPL
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Axel Hagermann
Lulea University of Technology
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Nicholas Attree
University of Stirling
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Matthew Adam Siegler
Planetary Sciences Institute
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William Bruce Banerdt
Jet Propulsion Laboratory
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Abstract

We use the surface temperature response to Phobos transits as observed by a radiometer on board of the InSight lander to constrain the thermal properties of the uppermost layer of regolith. Modeled transit lightcurves validated by solar panel current measurements are used to modify the boundary conditions of a 1D heat conduction model. We test several model parameter sets, varying the thickness and thermal conductivity of the top layer to explore the range of parameters that match the observed temperature response within its uncertainty both during the eclipse as well as the full diurnal cycle. The measurements indicate a thermal inertia of 103+48-24 Jm-2K-1s-1/2 in the uppermost layer of 0.2 to 4 mm, significantly smaller than the thermal inertia of 200 Jm-2K-1s-1/2 derived from the diurnal temperature curve. This could be explained by larger particles, higher density, or a very small amount of cementation in the lower layers.