95 research outputs found
Thermal Conductivity of the Martian Soil at the InSight Landing site from HP3 Active Heating Experiments
The heat flow and physical properties package (HP3) 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 HP3 mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 +/- 0.002 W/mK, 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 micrometer 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/m3, indicating soil porosities of 61
Mars Soil Properties from Phobos Eclipse Observations by InSight HP³ RAD
Mars surface temperature response to insolation variations constrains soil properties and indicates layering consistent with cementation at depth
The InSight HP3 Penetrator (Mole) on Mars: Soil Properties Derived from the Penetration Attempts and Related Activities
The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3–5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5–6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure – as was determined through an extensive, almost two years long campaign – was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign – described in detail in this paper – the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole tip finally reached a depth of about 37 cm, bringing the mole back-end 1–2 cm below the surface. It reversed its downward motion twice during attempts to provide friction through pressure on the regolith instead of directly with the scoop to the mole hull. The penetration record of the mole was used to infer mechanical soil parameters such as the penetration resistance of the duricrust of 0.3–0.7 MPa and a penetration resistance of a deeper layer (> 30 cm depth) of 4.9±0.4 MPa. Using the mole’s thermal sensors, thermal conductivity and diffusivity were measured. Applying cone penetration theory, the resistance of the duricrust was used to estimate a cohesion of the latter of 2–15 kPa depending on the internal friction angle of the duricrust. Pushing the scoop with its blade into the surface and chopping off a piece of duricrust provided another estimate of the cohesion of 5.8 kPa. The hammerings of the mole were recorded by the seismometer SEIS and the signals were used to derive P-wave and S-wave velocities representative of the topmost tens of cm of the regolith. Together with the density provided by a thermal conductivity and diffusivity measurement using the mole’s thermal sensors, the elastic moduli were calculated from the seismic velocities. Using empirical correlations from terrestrial
soil studies between the shear modulus and cohesion, the previous cohesion estimates were found to be consistent with the elastic moduli. The combined data were used to derive a model of the regolith that has an about 20 cm thick duricrust underneath a 1 cm thick unconsolidated layer of sand mixed with dust and above another 10 cm of unconsolidated sand. Underneath the latter, a layer more resistant to penetration and possibly containing debris from a small impact crater is inferred. The thermal conductivity increases from 14 mW/m K to 34 mW/m K through the 1 cm sand/dust layer, keeps the latter value in the duricrust and the sand layer underneath and then increases to 64 mW/m K in the sand/gravel layer below
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Interpreting Aspirational Forms: A Technography of 3d Printing
This thesis examines the coinciding of human values and the affordances of technological material as an active form of directed evolution. Considering an entangled person and technology as an assemblage, the investigation responds to the question of technological choice as it refers to discrete moments of change: why is it that the assemblage orients toward a specific future way of being? This research demonstrates the choice is discernible as a chain of dependent moments which circumscribe innovation. Owing to its highly adaptable ontology as a relation between people and technology, the ethnographic fieldwork for this study involved interviewing hobbyists of 3d printing about their relationship with the platform technology. This work finds that the chain of dependent moments which minimally describe evolution for the person-printer assemblage can be organized as three successive coincidences: a predisposition prior to a new entanglement, a turn in which the person and printer are interactive, and an aspirational form which emerges with a discernible future orientation. As this study is reactive to larger discussions of global anxiety around human progress and the reality of the Anthropocene, I argue that theorists of progress should adopt a posthuman perspective which contends with the discursive relation between human values and material affordances as a superior descriptive heuristic than a focus on human choice alone
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