Planetary mass and radius plane for small planets. The three L 98-59 planets are highlighted in the planetary mass and radius space along with a set of selected exoplanets, plus the Earth and Venus for comparison. The solid lines depict theoretical mass-radius curves from two component models of fully differentiated planetary interiors with fractional compositions by mass in water (H₂ O), silicate (MgSiO₃), and/or iron (Fe) (Zeng & Sasselov 2013). Each model’s interior composition is annotated above its respective curve.