Structure of the Earth decay of radioactive elements, and freezing of the inner core. Structure of the Earth The internal structure of the Earth is layered in spherical shells: an outer silicate solid crust, a highly viscous asthenosphere and mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. Scientific understanding of the internal structure of the Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of
ITS launch vehicle "evolved quite a bit" since the November 2016 articulation of the very large "ITS launch vehicle." A key driver of the new architecture is to make the new system useful for substantial Earth-orbit and cislunar launches so that the new system might pay for itself, in part, through commercial spaceflight activities in the near-Earth space zone. In September 2017, the new smaller design was revealed to be the diameter launch vehicle, referred to by its "code name" BFR, with similar core vehicle structure (carbon fiber), engines (Raptor), and Mars mission architecture; but explicitly aimed at superseding and replacing the entire