Publication Date:
2023-07-25
Description:
The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 [1] to in-situ measure the surface heat flow. Temperature sensors were to be installed at a target depth of 3–5m by a small penetrator, nicknamed the mole. A radiometer to measure the surface temperature complements the package. The mole, requiring friction on its hull to balance remaining recoil from its hammer mechanism, did not penetrate to the targeted depth. Instead, it reached a depth of 40cm, bringing the mole back-end 2–3cm below the surface. Lessons learned from the penetration failure have been discussed by [2]. The root cause of the failure - as was determined through an almost two years long campaign - was a lack of friction in an unexpectedly thick cohesive near-surface duricrust. The mole was used as a penetrometer and a thermal probe [3,4] instead and the hammering signals were recorded by the InSight seismometer [5]. Accordingly, the soil is highly porous and layered with a density of 1200kg/m3, thermal conductivity of 39mW/m K, cohesion between 4 and 25kPa, and s and p wave velocities of around 115 and 60m/s, respectively. The thermal conductivity varies with the season and the atmospheric pressure by +/-5% showing that gas in the pores contributes significantly to the heat transport. [1] Spohn et al. (2018) doi:10.1007/s11214-018-0531-4 [2] Spohn et al. (2022) doi:10.1016/j.asr.2022.02.009 [3] Spohn et al. (2022) doi: 10.1007/s11214-022-00941-z [4] Grott et al. (2021) doi:10.1029/2019EA000670 [5] Brinkmann et al. (2022) doi:10.1029/2022JE007229
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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