We investigate the geodynamic and melting history of Mars using 3D spherical shell models of mantle convection, constrained by the recent InSight mission results. The Martian mantle must have produced sufficient melt to emplace the Tharsis rise by the end of the Noachian–requiring on the order of 1–3×109 km3 of melt after accounting for limited (~10\%) melt extraction. Thereafter, melting declined, but abundant evidence for limited geologically recent volcanism necessitates some melt even in the cool present-day mantle inferred from InSight data. We test models with two mantle activation energies, and a range of crustal Heat Producing Element (HPE) enrichment factors and initial core-mantle boundary temperatures. We also test the effect of including a hemispheric (spherical harmonic degree-1) step in lithospheric thickness to model the Martian dichotomy. We find that a higher activation energy (350 kJ mol−1) rheology produces present-day geotherms consistent with InSight results, and of those the cases with HPE enrichment factors of 5–10x produce localized melting near or up to present-day. 10x crustal enrichment is consistent with both InSight and geochemical results, and those models also produce present-day geoid power spectra consistent with Mars. However, it is very difficult to produce sufficient melt to form Tharsis in a mantle that also matches the present-day geotherm, without assuming extremely efficient extraction of melt to the surface. The addition of a degree-1 hemispheric dichotomy, as an equatorial step in lithospheric thickness, does not significantly improve upon melt production or the geoid.

The heat flow and physical properties package measured soil thermal conductivity at the landing site in the 0.03 to 0.37 m depth range. Six measurements spanning solar longitudes from 8.0$^\circ$ to 210.0$^\circ$ were made and atmospheric pressure at the site was simultaneously measured using InSight’s Pressure Sensor. We find that soil thermal conductivity strongly correlates with atmospheric pressure. This trend is compatible with predictions of the pressure dependence of thermal conductivity for unconsolidated soils under martian atmospheric conditions, indicating that heat transport through the pore filling gas is a major contributor to the total heat transport. This implies that any cementation or induration of the soil sampled by the experiments must be minimal and that the soil surrounding the mole at depths below the duricrust is unconsolidated. Thermal conductivity data presented here are the first direct evidence that the atmosphere interacts with the top most meter of material on Mars.

The heat flow and physical properties package (HP$^3$) 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 HP$^3$ mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 $\pm$ 0.002 W m$^{-1}$ K$^{-1}$, 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 $\mu$m 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 m$^{-3}$, indicating soil porosities of 61 \%.