Chaos on Io: A model for formation of mountain blocks by crustal heating, melting, and tilting

Mountains are distributed across the surface of Io, the fiercely tidally he ated moon of Jupiter, The large crustal thicknesses implied by their great heights can be reconciled with Io's high heat how, if most of the heat esca pes directly via volcanic eruptions (the heat-pipe model), but the origin o f the mountains has remained obscure. Recent images show that many of Io's mountains are tilted blocks undergoing tectonic collapse, and we propose he re that the volcanic heat-pipe land continuous terrain burial) model natura lly leads to such unstable topography, That is, burial (1) generates horizo ntal tensile stresses as the volcanic crustal stack is loaded, (2) creates large horizontal compressive confining stresses as Io's crust subsides (mov es to a smaller effective radius), and importantly, (3) allows for potentia lly large horizontal compressive thermal stresses as the base of the crust reheats owing to fluctuations in the efficiency of the volcanic heat piping . Faulting associated with these stresses may raise mountain scarps directl y or in concert with thermal uplift due to the crustal reheating; continued crustal heating and melting then lead to mountain collapse tall over <1 m. y. to a few million years). Our model predicts that regions of active mount ain formation and volcanic activity on Io should be anticorrelated, which i s observed. Moreover, substantial tidal heating and disruption of planetary crust are seen elsewhere in the Jupiter system, in the chaos terrains of E uropa. There may be stronger commonalities between the two inner jovian moo ns land early Earth) than previously realized.