To determine which planet would gravitationally attract the spacecraft the least, we can look at the estimated mass of each planet. The gravitational attraction is directly related to the mass of the planet — the more massive the planet, the stronger its gravitational pull.
Based on the provided masses:
- Venus: 4.87 x 10²⁴ kg
- Mars: 0.642 x 10²⁴ kg
- Jupiter: 1,898.0 x 10²⁴ kg
- Neptune: 102.0 x 10²⁴ kg
Among these, Mars has the smallest mass (0.642 x 10²⁴ kg). Therefore, it would gravitationally attract the spacecraft the least.
The answer is: Mars.