What was the potential energy of the earth-spacecraft system?

Question

Ten days after it was launched toward Mars in December 1998, the Mars Climate Orbiter spacecraft (mass 629 kg) was

2.87 x 10^6 km from the earth and traveling at

1.20 x 10^4 km/h relative to the earth.

Answer 1

Potential energy U = -GMm/r

G = 6.67 x 10^-11 Mm^2/kg^2

M = 5.98 x 10^24 kg

m = 629 kg

r = 2.87 x 10^9 m

U = -8.7 x 10^7 J