Modeled internal energy balance for LP 791-18 d. Plotted are convective (blue curves) and tidal (black and red curves) heat fluxes as a function of the mantle’s potential temperature. The isothermal mantle solidus is set at T_p = 1600 K. We follow the prescription of Peterson et al. (2023) and use the same parameters therein to compute: i) the convective flux assuming soft turbulence in the mantle (e.g., Solomatov 2015), whereby the four sets of curves cover a range of melt fraction coefficients (B = 10, 20, 30, and 40); and ii) the tidal heating flux of a Maxwell viscoelastic solid mantle. In addition, we compute the tidal heat flux allowing for the fluid contribution of melt in the mantle, following Farhat et al. (2025), using a conservative estimate of the dissipative timescale, σ_R = 10⁻³ s⁻¹. Interior thermal equilibria, corresponding to the balance between tidal heating and convective cooling, are shown by the colored markers.