Density vs. mass of transiting super-Earths. The data for the known transiting super-Earths and mini-Neptunes are shown, as well as the relationships for the four rocky compositions considered in this study. Earth, Venus, Uranus and Neptune are shown for reference. The error bars for the density are calculated as ρ_min = 4π/3   (M − σM)/(R + σR)³ and ρ_max = 4π/3   (M + σM)/(R − σR)³.