Mass-radius diagram of planets smaller than ~2.8 R_⊕. The data points are shaded according to the precision on the mass, with a full color indicating a value better than 20%. Earth and Venus are shown for comparison. The dashed lines show planetary interior models for different compositions as labelled (Zeng et al. 2019). Planets are color-coded according to the incident flux Fp, relative to the solar constant F_⊙ The horizontal light-blue shade centered on R ~ 1.70 R_⊕ shows the radius Gap. The shaded gray region marks the maximum value of iron content predicted by collisional stripping (Marcus et al. 2010).