based on numerical calculations using laboratory data of physical material properties therefore aims at improving our understanding of the origins, evolutions, and current states of planets. In the case of the terrestrial planets and satellites within the solar system the resultant radial profiles of density and related material properties are required to be consistent with geophysical observations and cosmochemical evidence for the likely compositions of crust, mantle and core as obtained from measurements by interplanetary space probes. For terrestrial exoplanets, the numerical models have to be consistent with the observed planetary masses and radii measured from ground-based observations and space missions. Calculated models will be used to derive mass-radius relationships for exoplanets assuming a range of different mineralogical compositions to gain insight in the interior structure and possible bulk compositions of these planets. Furthermore, obtaining scaling laws for key physical and chemical properties will be essential for a better understanding of global planetary processes controlling the general evolution of a planetary body and its astrobiological potential to be life-sustaining.
Figure 1:Mass-radius relationships for solid exoplanets ranging from 1 to 17.5 times the mass of the Earth. The solid curves represent chemically homogeneous, self-compressible spheres of the following materials: water-ice (blue line), silicate (green line), and iron (red line). The dashed curves denote differentiated planets of various bulk compositions. The green dashed curve is for Earth-like planets with an iron core of 32.6 wt.-% and a 67.4 wt.-% silicate mantle. The blue dashed curve is for ocean planets using the Jovian moon Ganymede as a type-example, resulting in a 45 wt.-% water-ice shell surrounding a 48.5 wt.-% silicate mantle, and a 6.5 wt.-% iron core. The red dashed curve is for iron-rich planets like Mercury composed of a 70 wt.-% iron core overlain by a 30 wt.-% silicate mantle. The crosses represent the first low-mass exoplanets with a measured planetary radius and total mass according to their observational uncertainties. Source: F.W. Wagner et al. (2011), Icarus 214, 366-376.