Gravitational attraction is determined using G (m1m2)/r^2
Which indicates the force is inversely proportional to the square of separation of the bodies
Of the terrestrial planets Mercury, Venus, Earth, and Mars - Venus and Mars are immediate neighbours to Earth. Any quantity of missions have studied either.
Venerean gravity is almost 90% of Earth's own. Venus is also closer to Sol than Earth - figuratively downhill that is. All three bodies (Venus, Earth, Mars) being in motion there may be occasions when Mars is perhaps physically closer. Yet Venus appears to have the following advantages -
- Further downhill in the Solar System
- Masses almost the same as Earth; ergo larger sphere of influence
- Average separation from Earth ~25 M Miles (Mars average distance from Earth is ~140M Miles)
Does a mission to Venus orbit require less propellant than a similar mission to Mars with the same payload?