What can Olympus Mons tell us about the Martian lithosphere?

摘要

Under gravitational loading, a volcanic edifice deforms, and the underlying lithosphere downflexes. This has been observed on Earth, but is equally true on other planets. We use finite element models to simulate this gravity driven deformation at Olympus Mons on Mars. Eleven model parameters, including the geometry and material properties of the edifice, lithosphere and underlying asthenosphere, are varied to establish which parameters have the greatest effect on deformation. Values for parameters that affect deformation at Olympus Mons, Mars, are constrained by minimising misfit between modelled and observed measurements of edifice height, edifice radius, and flexural moat width. Our inferred value for the Young's modulus of the Martian lithosphere, 17.8 GPa, is significantly lower than values used previously, suggesting that the Martian lithosphere is more porous than generally assumed. The best-fitting values for other parameters: edifice density (2111 - 2389 kg.m(-3)) and lithosphere thickness (83.3 km) are within ranges proposed hitherto. The best-fitting values of model parameters are interdependent; a decrease in lithosphere Young's modulus must be accompanied by a decrease in edifice density and/or an increase in lithosphere thickness. Our results identify the parameters that should be considered within all models of gravity-driven volcano deformation; highlight the importance of the often-overlooked Young's modulus; and provide further constraints on the properties of the Martian lithosphere, namely its porosity, which have implications for the transport and storage of fluid throughout Mars' history. (C) 2020 The Authors. Published by Elsevier B.V.