On 5 March 1979, Voyager 1 made its closest approach of Jupiter. It passed the planet at a distance of 349,000 kilometers (217,000 miles).

Voyager 1 began Photographing Jupiter long before that approach. 

The photograph above was taken in December 1978 from a distance of 83 million km (or 52 million miles). 

Voyager 1 discoveries of Jupiter 

The biggest surprise was the discovery of volcanism on Io, one of Jupiter's moons. It was the first time that and active volcano was discovered in the Solar System outside Earth.

Here is a picture of volcano Loki erupting:

Activity on Io affects the whole Jovian system. Eruptions from Io's volcanos spread sulfur, oxygen and sodium into Jupiters magnetosphere.

Close up of a volcano and lava flows on Io.

Voyager 1 also photographed by another of Jupiter's moons: Europa. Taken from 3 million kilometers, show the surface unimpacted.

 Compare that to the cratered surface of Ganymede, Jupiter largest moon. The above photograph was taken from 253,000 km

 Voyager one stopped photographing Jupiter in April 1979.