In the 40 years since Voyager 1 and 2 departed Earth’s atmosphere, they have continually delivered answers to questions posed back at base.
Launched in August and September 1977, less than a fortnight apart (though not set off in chronological order), Voyager 1 and Voyager 2’s impact on scientific discovery continues to this day.
Voyager 1 is currently in what’s called ‘interstellar space’, around 20bn km from Earth.
Voyager 2, the first to depart Earth’s atmosphere, is in the ‘heliosheath’. This is the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas, almost 17bn km from home.
They are in daily communication with researchers back at NASA, too, bringing a number of incredible achievements since firing off our planet four decades ago.
Voyager 1 was the first spacecraft ever to reach interstellar space in 2012, with Voyager 2 still the only spacecraft to have flown by Jupiter, Saturn, Uranus and Neptune, with Pluto thrown in for good measure.
Between them, the duo discovered the first active volcanoes beyond Earth, on Jupiter’s moon Io; hints of a subsurface ocean on Jupiter’s moon Europa; the most Earth-like atmosphere in the solar system, on Saturn’s moon Titan; the jumbled-up, icy moon Miranda at Uranus; and ice-cold geysers on Neptune’s moon Triton.
And NASA seems to be in a celebratory mood right now.
“I believe that few missions can ever match the achievements of the Voyager spacecraft during their four decades of exploration,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate.
“They have educated us to the unknown wonders of the universe and truly inspired humanity to continue to explore our solar system and beyond.”
Voyager 1 has, throughout its trip, informed researchers that the heliosphere – the bubble-like volume containing our solar system’s planets and solar wind – effectively acts as a radiation shield for the planets.
Voyager 2 has been in the news more than Voyager 1 of late, with some of its discoveries playing a larger part in today’s space exploration missions.
An image it took of Uranus in 1986, as it neared the edge of our solar system, is still offering fascinating insights into the planetary make-up of our nearest and dearest neighbours.
A study late last year, led by University of Idaho researchers, suggested there could be two tiny, previously undiscovered moonlets orbiting near two of the planet’s rings.
“The technology is many generations old, and it takes someone with 1970s design experience to understand how the spacecraft operate and what updates can be made to permit them to continue operating today and into the future,” said Suzanne Dodd, Voyager project manager based at NASA’s Jet Propulsion Laboratory in Pasadena.
Both spacecraft will have their science instruments disengaged by 2030, though that’s not the end of Voyager 1 and 2.
Instead, they’ll be out on their own, travelling at 48,280kph, orbiting within the Milky Way every 225m years.