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Soil Thermophysical Properties Near the InSight Lander Derived From 50 Sols of Radiometer Measurements
Author(s) -
Piqueux Sylvain,
Müller Nils,
Grott Matthias,
Siegler Matthew,
Millour Ehouarn,
Forget Francois,
Lemmon Mark,
Golombek Matthew,
Williams Nathan,
Grant John,
Warner Nicholas,
Ansan Veronique,
Daubar Ingrid,
Knollenberg Jörg,
Maki Justin,
Spiga Aymeric,
Banfield Don,
Spohn Tilman,
Smrekar Susan,
Banerdt Bruce
Publication year - 2021
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2021je006859
Subject(s) - radiometer , albedo (alchemy) , geology , martian soil , atmospheric sciences , layering , environmental science , martian , mineralogy , remote sensing , mars exploration program , martian surface , astrobiology , physics , art , performance art , art history , botany , biology
Measurements from the InSight lander radiometer acquired after landing are used to characterize the thermophysical properties of the Martian soil in Homestead hollow. This data set is unique as it stems from a high measurement cadence fixed platform studying a simple well‐characterized surface, and it benefits from the environmental characterization provided by other instruments. We focus on observations acquired before the arrival of a regional dust storm (near Sol 50), on the furthest observed patch of soil (i.e., ∼3.5 m away from the edge of the lander deck) where temperatures are least impacted by the presence of the lander and where the soil has been least disrupted during landing. Diurnal temperature cycles are fit using a homogenous soil configuration with a thermal inertia of 183 ± 25 J m −2 K −1 s −1/2 and an albedo of 0.16, corresponding to very fine to fine sand with the vast majority of particles smaller than 140 μm. A pre‐landing assessment leveraging orbital thermal infrared data is consistent with these results, but our analysis of the full diurnal temperature cycle acquired from the ground further indicates that near surface layers with different thermophysical properties must be thin (i.e., typically within the top few mm) and deep layering with different thermophysical properties must be at least below ∼4 cm. The low thermal inertia value indicates limited soil cementation within the upper one or two skin depths (i.e., ∼4–8 cm and more), with cement volumes <<1%, which is challenging to reconcile with visible images of overhangs in pits.