Starting 35 years ago, our view of the solar system was forever changed. The launch of the Voyager 1 probe on Sept. 5, 1977 ushered in a golden era of planetary exploration. Along with its sister probe, Voyager 2, the spacecraft took the first detailed images of planets in the outer solar system, discovering magnificent rings, churning atmospheric processes, and volcanic activity on tiny moons. Voyager 2 actually launched on Aug. 20, slightly earlier than its counterpart, but took a longer route to reach Jupiter and Saturn after Voyager 1. The Voyager probes were a scaled-back version of a proposed “Grand Planetary Tour” mission, which would have used a rare alignment in the outer solar system to swing from planet to planet with minimal fuel. In the original plan, four spacecraft would have visited all the gas giants and even tiny Pluto (then still a planet). But without budgetary support from President Nixon and Congress, the ambitious mission was canceled. Since the 1977 planetary configuration occurred only once every 177 years, NASA engineers decided to go forward with a new plan — the Voyager probes, two identical robots that would travel to Jupiter and Saturn and, if successful, on to Uranus and Neptune. Voyager 1 ultimately performed a closer encounter with Saturn’s moon Titan that flung it out of the solar system, and only Voyager 2 made it to the latter planets. We’re lucky that both probes made it as far as they did, since data from these missions was unparalleled until the more recent Galileo and Cassini probes. Both Voyager 1 and 2 are still operational, becoming some of the most distant man-made objects ever built (Voyager 1 is currently 11 billion miles from the sun) and have enough power to keep going until 2025. Here we take a look at some of the best images and discoveries that these incredible probes produced during their flight through our solar system. Above: Great Red Spot A centuries-long storm rumbles through Jupiter’s atmosphere in this image from Voyager 1, taken in 1979. The Great Red Spot, which is large enough to swallow three Earths, is a persistent cyclone large enough to be seen with some backyard telescopes. Image: NASA/JPL

Jupiter’s Rings Jupiter’s faint rings make a remarkable appearance in this photo, taken through orange and violet filters to bring out the contrast. First imaged by the Voyager probes, the four rings are made mostly of fine dust and are spread out between an area about 60,000 to 140,000 miles from Jupiter. Image: NASA/JPL

Io’s Volcanoes The Voyager probes gave astronomers their first close-up peek of Jupiter's moons. The spacecraft discovered intense volcanic activity on Io caused by constant stretching and squeezing from Jupiter’s gravitational field. The above image shows a massive eruption from Io’s Loki Patera, a massive volcanic depression with an active lava lake. Below is a view of Ganymede, the largest moon in the solar system showing razed craters, bright rays, and young, clean surface ice. The photo below that shows long cracks in the surface of Europa, which indicate a deep subsurface ocean, a possible location to search for life in the solar system. Images: 1) NASA/JPL/USGS. 2) NASA/JPL. 3) NASA/JPL.

Saturn Shadow Voyager 1 made it to Saturn after a speedy three years, taking many incredible images, such as this one of the gas giant’s well-known ring system. This shot was taken as the probe departed Saturn, swinging its way out of the solar system. Image: NASA/JPL

Saturn and Moons Two of Saturn’s tiny moons can be seen in this impressive shot, along with the gas giant’s rings. The moons, Tethys (above) and Dione, are mostly composed of water ice. Saturn’s largest moon, Titan, can be seen in the image below, its surface obscured by thick orange clouds of methane and ethane. Images: 1) NASA/JPL. 2) NASA/JPL.

Saturn’s Rings False-color images (above) show off Saturn’s C- and B-rings in brilliant shades. High-resolution shots (below) also show off dark spoke-like features swirling around in the ring structure. Astronomers suspect that Saturn’s electromagnetic field is interacting with the rings in some way to produce these spokes but their ultimate cause remains a mystery. Images: 1) NASA/JPL. 2) NASA/JPL.

Saturn’s Atmosphere This image from Voyager 2 combines images taken in ultraviolet, violet, and green filters to bring out features in Saturn’s atmosphere. Changes in the atmosphere from Voyager 1’s pass a year earlier suggested seasonal variations taking place on the planet. Image: NASA/JPL

Uranus Farewell The aquamarine crescent of Uranus can be seen above in this parting shot from Voyager 2, taken in 1986. The spacecraft – the only probe to ever visit both Uranus and Neptune – discovered a number of the planet’s moons and provided close-up shots of its impressive ring system (below). Images: 1) NASA/JPL. 2) NASA/JPL

Uranus’ Moons The image above shows Uranus’ largest moon, Titania. Covered in impact scars, Titania is a cold gray world that also features many canyons and scarps. The patchwork surface of another moon, Miranda, can be seen in the photo below. Abundant features known as chevrons indicate past geologic activity. Images: 1) NASA/JPL. 2) NASA/JPL

Neptune in Full Voyager 2 is the only spacecraft to visit distant Neptune, the farthest planet in our solar system, arriving in 1989. This full image (above) shows the planet’s Great Dark Spot, a hole in Neptune’s methane clouds that appears and disappears periodically. Below is a closer shot of the structure, with feathery white clouds that lie along its edge. Images: 1) NASA/JPL. 2) NASA/JPL

Triton’s Surface This enormous mosaic shows the surface of Neptune’s largest moon Triton in exquisite detail. The moon’s surface is the coldest recorded place in the solar system, with temperatures reaching -391 degrees Fahrenheit. The moon is covered mostly in nitrogen ice, though pinkish deposits of methane ice can also be seen. Image: NASA/JPL/USGS