A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

A series of round-robin measurements of the self-field ac loss of Bi-2223 tapes

A round-robin of self-field ac loss measurements on Bi-2223 tapes has been performed for the first time, under the Brite EuRam research programme SACPA. Excellent agreement on loss data has been obtained by the four measurement partners. This further confirms the validity of the electrical technique employed and allows reliable comparisons between the loss data of the individual partners in the project. The different measurement systems and sample mounting procedure are described. For accurate measurement of the loss voltage to the required sensitivity, only a lock-in technique was suitable. The phase of the applied current was measured with a Rogowski coil (with or without compensation) or a non-inductive resistor