This past September marked the 40th year in space for NASA’s twin probes: Voyager 1 and Voyager 2. Since the two first left Earth in 1977, they have traveled more than 10 billion miles, exploring our solar system’s planets and beyond.
The initial mission was to explore Jupiter and Saturn. Voyager 1 arrived at Jupiter in January of 1979, despite being launched 16 days after Voyager 2, while Voyager 2 arrived in July of 1979. Voyager 1 flew very close to Jupiter and was able to observe Jupiter’s moons, rings, and magnetic fields among other aspects of Jupiter’s surroundings. The probe is credited with the extraordinary discovery of volcanoes on Jupiter’s moon, Io. This was the first documentation of volcanic activity outside of Earth. In April of 1979, it left Jupiter, with Voyager 2 following closely behind. When Voyager 2 arrived at Jupiter, it explored Jupiter’s Great Red Spot and discovered that storm was anticyclonic. This means that Jupiter’s storms form in high-pressure systems rather than low-pressure systems. It also observed additional volcanic activity as it flew by Io and collected data on Jupiter’s rings. Voyager 2 finally departed from Jupiter in August of ’79.
Both probes traveled to Saturn, where they observed its atmosphere, moons, and rings. Voyager 1 analyzed Saturn’s atmosphere and found that it mainly consists of hydrogen, with less than 10% of helium. Winds on the planet could blow at about 1,100 mph, and the day lasted 24 hours. Voyager 2 recorded that the upper atmosphere of the planet had a temperature of -203˚C, while the lower atmosphere had a temperature of -130˚C. Voyager 1 performed a flyby of Titan, one of Saturn’s moons, and attempted to determine the makeup of its atmosphere. While it was too hazy, the data suggested that it contained liquid hydrocarbons on the surface. As Voyager 1 continued toward interstellar space, Voyager 2 received an extended mission to complete a flyby of Uranus and Neptune.
In January of 1984, Voyager 2 reached Uranus and conducted studies on the planet’s atmosphere/rings and moons. It managed to discover 11 moons orbiting Uranus and recorded a 17-hour day. Voyager 2’s biggest discovery, however, was the presence of a magnetic field. Data showed that the tilted axis of the planet made the end of the magnetotail a corkscrew shape, as opposed to being straight like Earth’s. When Voyager went to Neptune in August of 1989, NASA decided to observe the planet as well as perform a fly-by of Triton. The probe discovered a Great Dark Spot, which has since disappeared. Scientists believe it was simply an opening in the clouds of Neptune that made it appear as a large spot. On Triton, data revealed that it had a denser atmosphere and a jagged terrain full of channels, ridges, and craters. Afterward, it flew toward the heliosphere, or the outer part of solar system.
In August of 2012, Voyager 1 was the first man-made object to fly into interstellar space, which is the area between solar systems that includes gasses, dust, and cosmic rays. Voyager 2 is still making its way through the outermost part of our solar system.
Both are prepared for anything — even communication. Each Voyager carries a golden disc with recordings from Earth (including “hello” in 55 languages, sounds from both nature and humans, and musical artists from Mozart to Chuck Berry). Despite all the progress the probes have made, their programs at NASA are scheduled to end between 2025-2030, as they are running low on power. For now, they continue to send back information as they fly deeper into space.