sentences:  A study on Gliese 876 d by a team around Diana Valencia revealed that it would be possible to infer from a radius measured by the transit method of detecting planets and the mass of the relevant planet what the structural composition is.For Gliese 876 d, calculations range from 9,200 km (1.4 Earth radii) for a rocky planet and very large iron core to 12,500 km (2.0 Earth radii) for a watery and icy planet.Within this range of radii the super-Earth Gliese 876 d would have a surface gravity between 1.9g and 3.3g (19 and 32 m/s2).