The effect of impurities on the electrical resistivity of Fe at core conditions is controversial due to the challenges of measuring transport properties of Fe alloys under high‐pressure and high‐temperature conditions. In this study we describe an innovative technique to make wires of Fe‐Si samples initially in powder form for measuring electrical resistivity. The electrical resistivity of Fe‐2, Fe‐8.5, and Fe‐17 wt%Si was measured at 3, 4, and 5 GPa at temperatures into the liquid state and compared to results of Fe‐4.5 wt%Si and Fe from prior studies. Isothermal electrical resistivity increases linearly with increasing Si content. Yet the effect of Si content on the magnitude of the electrical resistivity compared to that of Fe diminished as temperature increased at all experimental pressures. This implies the contribution to the electrical resistivity due to Si impurities is dependent on temperature, in disagreement with Matthiessen's rule. Thermal conductivity of Fe‐Si alloys calculated using the Wiedemann‐Franz law indicates a nonnegligible influence of the Si content on the thermal conductive properties of Fe‐Si alloys. The results are used to calculate the adiabatic heat flux of an Fe‐Si lunar core and date the end of the high magnetic field intensity era of the lunar dynamo to be in the range 3.32–3.80 Ga.

There is a considerable amount of literature on the electrical resistivity of iron at Earth’s core conditions, while only few studies have considered iron and iron-alloys at other planetary core conditions. Much of the total work has been carried out in the past decade and a review to collect data is timely. High pressures and temperatures can be achieved with direct measurements using a diamond-anvil cell, a multi-anvil press or shock compression methods. The results of direct measurements can be used in combination with first-principle calculations to extrapolate from laboratory temperature and pressure to the relevant planetary conditions. This review points out some discrepancies in the electrical resistivity values between theoretical and experimental studies, while highlighting the negligible differences arising from the selection of pressure and temperature values at planetary core conditions. Also, conversions of the reported electrical resistivity values to thermal conductivity via the Wiedemann-Franz law do not seem to vary significantly even when the Sommerfeld value of the Lorenz number is used in the conversion. A comparison of the rich literature of electrical resistivity values of pure Fe at Earth’s core-mantle boundary and inner-core boundary conditions with alloys of Fe and light elements (Si, S, O) does not reveal dramatic differences. The scarce literature on the electrical resistivity at the lunar core suggests the effect of P on a wt% basis is negligible when compared to that of Si and S. On the contrary, studies at Mercury’s core conditions suggest two distinct groups of electrical resistivity values but only a few studies apply to the inner-core boundary. The electrical resistivity values at the Martian core-mantle boundary conditions suggest a negligible contribution of Si, S and O. In contrast, Fe-S compositions at Ganymede’s core-mantle boundary conditions result in large deviations in electrical resistivity values compared to pure Fe. Contour maps of the reported values illustrate ρ(P, T) for pure Fe and its alloys with Ni, O and Si/S and allow for estimates of electrical resistivity at the core-mantle boundary and inner-core boundary conditions for the cores of terrestrial-like planetary bodies.

Electrical resistivity measurements of Fe–10wt%Ni–10wt%Si have been performed in a multi-anvil press from 3 to 20 GPa up to 2200 K. The temperature and pressure dependences of electrical resistivity are analyzed in term of changes in the electron mean free path. Similarities in the thermal properties of Fe–Si and Fe–Ni–Si alloys suggest the effect of Ni is negligible. Electrical resistivity is used to calculate thermal conductivity via the Wiedemann–Franz law, which is then used to estimate the adiabatic heat flow. The adiabatic heat flow at the top of Earth’s core is estimated to be 14 TW from the pressure and temperature dependences of thermal conductivity in the liquid state from this study, suggesting thermal convection may still be an active source to power the dynamo depending on the estimated value taken for the heat flow through the core mantle boundary. The calculated adiabatic heat flux density of 22.7–32.1 mW/m² at the top of Mercury’s core suggests a chemically driven magnetic field from 0.02 to 0.21 Gyr after formation. A thermal conductivity of 140–148 Wm⁻¹ K⁻¹ is estimated at the center of a Fe–10wt%Ni–10wt%Si Venusian core, suggesting the presence of a solid inner core and an outer core that is at least partially liquid.

Geodesy is a very active and essential research discipline in geophysics but it is not a commonly studied subject at the secondary school or junior post-secondary levels. Far more frequently, gravity and gravitational acceleration are discussed, to some extent, in elementary kinematics or classical mechanics courses. This often takes the form of the force acting on a body or bodies due to gravity, or that the acceleration (agrav) of a free-falling body is 9.8(1) m/s2—which implies the setting of the question is at Earth’s surface. While the latter is a reasonable and practical approximation, agrav observed over the surface of Earth varies and is dependent on several factors. These are normally related to elevation and latitude variations caused by Earth’s rotation. Earth’s rotation contributes negatively to agrav at the equator due to the centrifugal force outward and equatorial bulge, which makes the equatorial radius larger than the polar radius. Offsetting this partially is the positive contribution to agrav at the equator caused by the equatorial bulge because of the extra mass comprising the bulge.

Raman spectroscopy is a rapid, nondestructive analysis technique used in various scientific disciplines, including mineralogy, chemistry, materials science, and biology. The analysis of Raman spectra and the identification of specific substances in unknown samples can be complex and time-consuming due to the large database of Raman spectra. The Raman Match application was developed to simplify and automate the sample identification process through a search and match method. The application integrates the well-established RRUFF Raman database with the Python programming language. It provides a user-friendly graphical interface to load Raman spectra, identify and fit peaks, match peaks to the reference libraries, visualize the results, and generate publication-ready figures. The application offers a swift and automated method for mineral identification using Raman spectroscopy in laboratory and field settings and during planetary exploration missions to extraterrestrial environments with constraints on time and resources.