The gravitational potential at a point in the gravitational field due to a body can also be defined as the potential energy of an unit mass placed at that point. The highest value of the potential (gravitational) is zero at infinity, and so also of the gravitational potential energy. $$ V_{ab} = V_b - V_a = -\int^{r_b}_{r_a} E.dr $$ \(V_{ab} = \) potential difference (gravitational) between points a and b, \(r_a = \) distance of ‘a’ from the centre of the body, \(r_b = \)distance of ‘b’ from the centre of the body.