Jovian and Saturnian satellites

The years 1983‐1987 follow mankind's epochal first spacecraft encounters with the giant planets Jupiter and Saturn. Possibly the most spectacular “discoveries” there were the diversity and level of geological activity on the satellites that circle each. And part of the excitement no doubt stemmed from rebuttal of pre‐encounter preconceptions, as the satellites of the inner solar system, while fascinating, are geologically dead. Consequently, an entirely new branch of solar system science has opened up, one that is fascinating in its own right, and one that promises to greatly aid understanding of the origin and evolution of the Earth, the solar system, and life itself.