The Voyager programme was launched by NASA in 1977 to take advantage of a favourable alignment of Jupiter, Saturn, Uranus and Neptune. Although their original mission was to study only the planetary systems of Jupiter and Saturn, Voyager 2 continued on to Uranus and Neptune. Data and photographs collected by the Voyagers’ cameras, magnetometers and other instruments, revealed unknown details about each of the four giant planets and their moons.
Brian Cox revealed during his BBC series “The Planets” how NASA made a particularly bizarre find on Neptune.
He said last month: “It took 12 years, but Voyager finally crossed the great expanse of space between Earth and the most distant planetary system.
“Neptune – 17 times the mass of the Earth and even more massive than Uranus.
“But in contrast to its sister planet, Neptune’s atmosphere is bursting with activity.
“What we found was a planet of extreme weather, where high altitude winds whip white methane clouds at speeds of over 2,000 km/h.
“Those are the highest wind speeds anywhere in the Solar System.”
Dr Cox went on to reveal how the space agency is still baffled by the weather found on Neptune.
He added: “And Voyager saw a great dark spot, not unlike Jupiter’s great red spot.
“A storm system the size of Earth that, when looked at only four or five years later, we found had vanished.
“But over the years we’ve observed more storms raging over the planets.
“It’s one of the great mysteries of planets.”
Dr Cox also revealed how the same mission revealed Uranus has rings “just like Saturn”.
“Almost nine years after leaving Earth, Voyager approached an entirely new class of planet.
“Just like Jupiter and Saturn, the planet’s upper atmosphere is composed mostly of swirling hydrogen and helium gas and hidden beneath lies an exotic, icy mix of methane, ammonia and water.
“Voyager spent just six hours with Uranus and as its gaze widened it took in the entire system.
“And just like Saturn, Uranus has rings.
“But the rings are so dark, so faint that they’re very difficult to see from Earth.”