Compressional sound velocity as a function of density. Violet crossed diamonds (Crowhurst et al., 2004); blue open diamonds (Decremps et al., 2014); red open circles (Antonangeli et al., 2004b; 2012); green lined circles (Ohtani et al., 2013). The star is the ultrasonic determination reported in (Mao et al., 1998). PREM is shown as crosses. The solid line is a linear regression across all experimental data (V
P = a + bρ where a = −4,000 ± 110 m/s and b = 1.206 ± 0.011 m4/(kg s)).