  Planetary formation models predict the existence of massive terrestrial
planets and experiments are now being designed that should succeed in
discovering them and measuring their masses and radii. We calculate internal
structures of planets with one to ten times the mass of the Earth
(Super-Earths) in order to obtain scaling laws for total radius, mantle
thickness, core size and average density as a function of mass. We explore
different compositions and obtain a scaling law of $R\propto M^{0.267-0.272}$
for Super-Earths. We also study a second family of planets, Super-Mercuries
with masses ranging from one mercury-mass to ten mercury-masses with similar
composition to the Earth's but larger core mass fraction. We explore the effect
of surface temperature and core mass fraction on the scaling laws for these
planets. The scaling law obtained for the Super-Mercuries is $R\propto
M^{\sim0.3}$.
