Studying the Weather from the Inside
Gazing across the vast distances of the cosmos, two planets seemed likely targets for early atmospheric explorers, Mars and Venus. Both were fairly accessible, being the closest planets around. Venus was an easier target to get to. The planet’s path takes it around the Sun at an average distance of 67 million miles, compared to Earth’s 93 million miles. At times, the planets are a scant 23.7 million miles apart. An added attraction of Venus is that it is “downhill.” Things in the Solar System tend to fall toward the Sun. A spacecraft is no different. Since Venus is closer to the Sun than Earth is, the Sun’s gravity helps speed a Venus-bound spacecraft, while a Mars-bound one is fighting against the Sun’s gravity, going outward. All these factors meant that a trip to Venus would take roughly 4 months, while a trip to Mars could take as long as eight. In the early days of space exploration, a few extra months often meant the difference between success and failure.