Planets and satellites can be subjected to physical libration, which consists in forced periodic variations in their rotation rate induced by gravitational interactions with nearby bodies. Many bodies librate, such as Mercury, the Moon, Europa, Io or Enceladus. Can such complex motions act to generate flows in low viscosity interior fluid layers such as subsurface oceans and metallic liquid cores? It is typically assumed in planetary geophysics that fluid motions must be affiliated with buoyancy anomalies. However, our lab-numerical experiments show that, even in a shell geometry which is more relevant to model planetary liquid layers, mechanically forced flows can also drive bulk filling turbulence.