  Impact craters exist on solid surface planets, their satellites and many
asteroids.The aim of this paper is to propose a theoretical expression for the
product $\rho r^{3} v_{1}^{2}$,where the three symbols denote the mass
density,radius and speed of the impactor. The expression is derived using well
known results of solid state physics,and it can be used in estimating
parameters of impactors which have led to formation of craters on various solid
bodies in the Solar System.
