Laboratory investigation of mechanical energy dissipation relevant to rocky interiors of small icy moons

The habitability of icy moons in the outer Solar System is linked to their ability to maintain warm subsurface oceans through time, but the mechanisms leading to heat generation in small icy moons are not well constrained. While most heat generation in response to tidal forcing is thought to occur in icy crusts and water oceans, the deformation of chondritic material thought to make up rocky cores and mantles has not previously been studied comprehensively in a laboratory setting under relevant planetary conditions. We experimentally deformed samples of the Kilabo meteorite, an LL6 chondrite, under axial strain rates of 10^-5 s^-1 and confining pressures up to 100 MPa. We recorded the strength of the material, measured energy dissipation through acoustic emission events, and observed ultrasonic wavespeeds as a function of confining pressure. Our results suggest that dissipative brittle deformation is possible even during isotropic pressurization, as well as at low stresses and strains during nominally “elastic” deformation, due to the porous nature of the material. However, energetic acoustic emission events associated with brittle deformation become less powerful as confining pressure increases. The mechanical behavior of the meteoritic material also evolved as a function of increasing confining pressure: peak strength occurred at 50 MPa confining pressure, and material continuously stiffened as pressure increased. These pressure-dependent properties indicate that larger icy moons could have stiffer, less deformable silicate layers than those found in small icy moons, corresponding to a lower relative contribution of silicate deformation to the bodies’ total heat budgets. Future experiments on carbonaceous chondrites under oscillatory loading conditions are necessary to fully measure the potential magnitude of tidal heating in rocky silicate cores of icy moons.