The third unmanned probe to make an approach to the largest planet of the solar system did so on this day in history.
Voyager 1, launched in 1977, made its closest approach to Jupiter on March 5th, 1979. It began its study of the planet earlier in that year. Aside from close-up images of the Great Red Spot and other features of the gas giant, it also studied some of the moons of Jupiter in details.
One of the major discoveries that Voyager 1 made was the find of sulfuric volcanoes on the moon of Io.
Voyager 1 went on to encounter Saturn. More probes, including Voyager 2, would encounter Jupiter as well throughout the next years and decades.