Which planet's exploration was highlighted as a significant scientific achievement of the 20th century by the Pioneer and Voyager spacecraft?

The exploration of Saturn by the Pioneer and Voyager spacecraft is recognized as a significant scientific achievement of the 20th century due to the comprehensive data and stunning imagery they provided about this complex gas giant and its unique features. Voyager 1 and Voyager 2, in particular, made groundbreaking discoveries, including detailed information about Saturn's rings and its many moons, such as Titan, which has a substantial atmosphere and hydrocarbon lakes.

The missions contributed enormously to our understanding of the planet’s magnetosphere, atmospheric dynamics, and its intricate system of rings. This wealth of information paved the way for future exploration and deepened our understanding of planetary science, furthering the field immensely. The high-resolution images and data provided by the spacecraft remain a crucial part of our scientific knowledge about Saturn.