Fifteenth Anniversary of Voyager 2 Flyby of Uranus in 1986
29 Jan 2001
(Source: Jet Propulsion Laboratory)
Posted by Larry Klaes from the History of Astronomy Discussion Group
The first unmanned space probe flyby in history of the planet Uranus by Voyager 2 on January 24, 1986 should have been an exciting one in the history of planetary exploration:
- Uranus was the first planet discovered by humans not thousands of years before written history and civilization, but in relatively moderns times - on March 13, 1781 by German musician turned English astronomer William Herschel, to be exact. I know others may have viewed Uranus telescopically before Herschel, be he was the first one to figure out that it was a planet and not a comet or star. Theoretically one could see Uranus with unaided vision from Earth, but it would have been too dim for our ancestors to really notice it, even in their non-light polluted night skies (at least none ever said they did that made it to our time).
- Uranus was later found to be a world tipped on its side compared to the rest of the known planets in the Sol system. Only later did astronomers learn that Pluto was tipped even moreso on its side and Venus was knocked all the way around from our perspective. With an axial tilt of almost 98 degrees (compare this to Earth's 23.5 degree tilt), Uranus' poles spend roughly half their time in the planet's 84-year solar orbit either in constant darkness or light.
- The discovery of a ring system around Uranus in 1977 gave the first real evidence that, rather than being unique to Saturn, ring systems around Jovian worlds are probably common. Indeed, the next few years - thanks to the Voyager probes - would show that these rings were indeed standard features for all of the gas giant planets of our Sol system.
- The five known moons of Uranus were virtually unknown little worlds, but after the Voyager probes' experiences with the exciting satellites of Jupiter and Saturn from 1979 through 1981, it was assumed they too would hold exciting new surprises for us.
- Voyager 2 was not meant to visit Uranus after Saturn, having already come from a scaled-down version of the Grand Tour of the outer planets. However, since Voyager 1 did make it to Saturn and perform a close examination of its largest moon Titan, Voyager 2 was given the go-ahead to Uranus and eventually Neptune in 1989 (it should be noted that Voyager 2 also survived being shut off in 1981 to allegedly save some bucks by the Reagan Administration, I kid you not). So with this rare bonus in hand, scientists were most eager to get their first close-up views of this bizarre alien world way out in the outer Sol system. But fate likes to play games with human expectations, and the Universe itself certainly does not cater to our wants and desires. The Voyager 2 mission to Uranus did go off as planned, but its two main problems had nothing to do with the space probe itself:
- Uranus itself did not turn out to be as "exciting" as the other two previously explored Jovian worlds, Jupiter and Saturn. The clouds were a bland and featureless shade of blue. The rings were dark and thin. The moons did not look much different from the other icy satellites of Jupiter and especially Saturn. Miranda was the only real exception, looking like a world that had been literally torn apart and smashed back together, complete with 20-kilometer high sheer ice cliffs.
One would think that exploring any new world for the first time in what was (and still is) the early days of our testing the waters of deep space would be exciting enough, but somehow the public and press had gotten spoiled by the amazing wonders at Jupiter and Saturn (not to mention many space-based science fiction flicks), and Uranus was just not cutting the bill, even if it was tipped on its side.
- The other deflecting event took place just four days after Voyager 2's closest flyby: The Space Shuttle Challenger 51-L mission ended tragically before it could even get into Earth orbit, where a leak in a solid rocket booster acted like a torch on the external fuel tank and caused it to explode, turning the shuttle into scrap metal and killing the seven astronauts on board - one of whom was going to be the first teacher in space.
This flight alone killed more astronauts than all previous manned space tragedies combined: The lone cosmonaut of Soyuz 1 in 1967 and the three cosmonauts of Soyuz 11 who had just returned from a thirty-day stay on the Soviet Salyut 1 space station in June of 1971 (the three astronauts of the Apollo 1 crew were killed in a fire during a ground test in 1967).
Needless to say, the press attention almost immediately evaporated from the lone space robot and the dull world it had been monitoring over two billion kilometers away to Cape Canaveral and NASA and did not come back.
Despite all this negativity from the general human perspective towards the Voyager 2 Uranus encounter, many new and important items were learned about this new world. Among them was the discovery of ten new moons circling the planet, a powerful magnetic field tipped sixty degrees to the planet's axis, and strong evidence that the outer Sol system went through a very violent period of collisions with other celestial bodies in the early days of our system's creation, judging by what happened to Uranus' moons and the planet itself, having been knocked completely on its side.
While Voyager 2 certainly did give us more information on Uranus than all previous Earth-based studies combined, no quick flyby can do what an orbiting probe can, as Galileo has certainly shown with Jupiter since 1995 and Cassini will with Saturn starting in 2004.
Though I would certainly like to be proven wrong here, there are no serious plans to orbit or even visit Uranus again any time soon.
For more on the Voyager 2 mission to Uranus, read here:
For more on the Voyager probes, go here and scroll down a bit for the Uranus encounter information:
Web sites on Uranus: