 Voyager 1 began photographing Jupiter in January 1979 and made its closest approach on March 5 , 1979 , at a distance of 349 @,@ 000 km from Jupiter 's center . This close approach allowed for greater image resolution , though the flyby 's short duration meant that most observations of Jupiter 's moons , rings , magnetic field , and radiation environment were made in the 48 @-@ hour period bracketing the approach , even though Voyager 1 continued photographing the planet until April . It was soon followed by Voyager 2 , which made its closest approach on July 9 , 1979 , 576 @,@ 000 km away from the planet 's cloud tops . The probe discovered Jupiter 's ring , observed intricate vortices in its atmosphere , observed active volcanoes on Io , a process analogous to plate tectonics on Ganymede , and numerous craters on Callisto . 
 Voyager 1 began photographing Jupiter in January 1979 and made its closest approach on March 5 , 1979 , at a distance of 349 @,@ 000 km from Jupiter <a href='null_genetive' title='1'><mark>'s</mark></a>center . This close approach allowed for greater image resolution , though the flyby <a href='null_genetive' title='2'><mark>'s</mark></a>short duration meant that most observations of Jupiter <a href='null_genetive' title='3'><mark>'s</mark></a>moons , rings , magnetic field , and radiation environment <a href='uninflect' title='4'><mark>were</mark></a> made in the 48 @-@ hour period bracketing the approach , even though Voyager 1 continued photographing the planet until April . It was soon followed by Voyager 2 , which made its closest approach on July 9 , 1979 , 576 @,@ 000 km away from the planet <a href='null_genetive' title='5'><mark>'s</mark></a>cloud <a href='uninflect' title='6'><mark>tops</mark></a> . The probe discovered Jupiter <a href='null_genetive' title='7'><mark>'s</mark></a>ring , observed intricate vortices in its atmosphere , observed active volcanoes on Io , a process analogous to plate tectonics on Ganymede , and numerous craters on Callisto . 
Voyager 1 began photographing Jupiter in January 1979 and made its closest approach on March 5 , 1979 , at a distance of 349 @,@ 000 km from Jupiter  center . dis close approach allowed fa greater image resolution , though the flyby  short duration meant that most observations of Jupiter  moons , rings , magnetic field , and radiation environment was made in the 48 @-@ hour period bracketing the approach , even tho Voyager 1 continued photographing da planet until April . It was soon followed by Voyager 2 , which made its closest approach on July 9 , 1979 , 576 @,@ 000 km away from tdaplanet  cloud top . The probe discovered Jupiter  ring , observed intricate vortices in its atmosphere , observed active volcanoes on Io , a process analogous to plate tectonics on Ganymede , and numerous craters on Callisto .