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The InSight-HP³ mole on Mars: Lessons learned from attempts to penetrate to depth in the Martian soil

Spohn, T. and Hudson, Troy L. and Witte, Lars and Wippermann, Torben and Wisniewski, Lukasz and Kedziora, Bartosz and Vrettos, C. and Lorenz, Ralph D. and Golombek, M. and Lichtenheldt, Roy and Grott, M. and Knollenberg, Jörg and Krause, Christian and Fantinati, Cinzia and Nagihara, S. and Grygorczuk, J. (2022) The InSight-HP³ mole on Mars: Lessons learned from attempts to penetrate to depth in the Martian soil. Advances in Space Research (69), pp. 3140-3163. Elsevier. doi: 10.1016/j.asr.2022.02.009. ISSN 0273-1177.

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The NASA InSight lander mission to Mars payload includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow. The package was designed to use a small penetrator - nicknamed the mole - to implement a vertical string of temperature sensors in the soil to a depth of 5 m. The mole itself is equipped with sensors to measure a thermal conductivity-depth profile as it proceeds to depth. The heat flow is calculated from the product of the temperature gradient and the thermal conductivity. To avoid the perturbation caused by annual surface temperature variations, the measurements need to be taken at a depth between 3 m and 5 m. The mole is designed to penetrate cohesionless soil similar in rheology to quartz sand which is expected to provide a good analogue material for Martian sand. The sand would provide friction to the buried mole hull to balance the remaining recoil of the mole hammer mechanism that drives the mole forward. Unfortunately, the mole did not penetrate more than 40 cm, roughly a mole length. The failure to penetrate deeper is largely due to a cohesive duricrust of a few tens of centimeter thickness that failed to provide the required friction. Although a suppressor mass and spring as part of the mole hammer mechanism absorb much of the recoil, the available mass did not allow designing a system that fully eliminated the recoil. The mole penetrated to 40 cm depth benefiting from friction provided by springs in the support structure from which it was deployed and from friction and direct support provided by the InSight Instrument Deployment Arm. In addition, the Martian soil provided unexpected levels of penetration resistance that would have motivated designing a more powerful mole. The low weight of the mole support structure was not sufficient to guide the mole penetrating vertically. Roughly doubling the overall mass of the instrument package would have allowed to design a more robust system with little or no recoil, more energy of the mole hammer mechanism and a more massive support structure. In addition, to cope with duricrust a mechanism to support the mole to a depth of about two mole lengths should be considered.

Item URL in elib:https://elib.dlr.de/186344/
Document Type:Article
Title:The InSight-HP³ mole on Mars: Lessons learned from attempts to penetrate to depth in the Martian soil
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Spohn, T.UNSPECIFIEDhttps://orcid.org/0000-0002-9322-6660UNSPECIFIED
Hudson, Troy L.UNSPECIFIEDhttps://orcid.org/0000-0002-5879-6633UNSPECIFIED
Witte, LarsUNSPECIFIEDhttps://orcid.org/0000-0002-3921-2524UNSPECIFIED
Wippermann, TorbenUNSPECIFIEDhttps://orcid.org/0000-0002-0354-6557UNSPECIFIED
Lorenz, Ralph D.Johns Hopkins University, Applied Physics Lab., Laurel, MD 20723, USAUNSPECIFIEDUNSPECIFIED
Golombek, M.Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USAhttps://orcid.org/0000-0002-1928-2293UNSPECIFIED
Lichtenheldt, RoyUNSPECIFIEDhttps://orcid.org/0000-0002-2539-4910UNSPECIFIED
Grott, M.UNSPECIFIEDhttps://orcid.org/0000-0002-8613-7096UNSPECIFIED
Knollenberg, JörgUNSPECIFIEDhttps://orcid.org/0000-0003-1249-8582UNSPECIFIED
Date:10 February 2022
Journal or Publication Title:Advances in Space Research
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 3140-3163
Keywords:InSight mission; heat flow probe; penetrator; Martian soil; planetary exploration
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project InSight - HP3
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Space Systems > Land and Exploration Technology
Institute of System Dynamics and Control > Space System Dynamics
Space Operations and Astronaut Training > User center for space experiments (MUSC)
Institute of Planetary Research > Planetary Sensor Systems
Institute of Planetary Research > Planetary Physics
Deposited By: Witte, Dr. Lars
Deposited On:09 May 2022 09:51
Last Modified:30 Jan 2024 11:10

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