I’ll just come out and say it – I love Voyager.
And no, I’m not referring to the Star Trek series, I’m talking about the original JPL/NASA spacecraft! Lately I’ve been posting some of the Voyager images I worked on here on my Science Blog, I’ve finally got my Voyager for POVray code back online, and only yesterday Voyager 2 edged over being 13 light-hours from Earth according to its twitter feed (this, I might add, is quite a long way – just over 93.85 AU!). So I guess I’m on a Voyager kick at the moment 😉
It’s hard to believe that back in the 1970s, we knew very little about the outer solar system. Even by the mid 80s, Uranus, Neptune and Pluto each got a couple of pages at most in an astronomy textbook because of that – but the Voyager spacecraft literally re-wrote those text books. In my opinion, they pretty much were responsible for the creation of Planetary Science as a rich field of study because they revealed a bewildering variety of new worlds for us to understand – and I was growing up while this revolution was going on. It’s largely because of Voyager that I got into astronomy and planetary science in the first place, so I owe it a lot :).
Voyager showed us the turbulent, changing atmosphere of Jupiter. It showed us the craters and impact basins of Callisto, the bright sulci and dark terrain of Ganymede, and the mysteriously smooth, cracked surface of Europa. One of my earliest memories is of watching Patrick Moore talk about Io’s active volcanoes, during live TV coverage while the images were coming in from Voyager 1 in 1979 (one fun story is that the active volcanism was predicted in a scientific paper that was published a matter of days before the flyby confirmed them!).
Two years later in 1981, Saturn was revealed to us, along with Titan’s thick atmosphere, Enceladus’ patchwork terrain of craters and grooves, Mimas’ similarity to the Death Star, the bright and dark faces of Iapetus, spokes and braids in Saturn’s rings and of course majestic Saturn itself. Voyager 1 subsequently went on a path that took it out of the solar system after that, but Voyager 2 continued to Uranus and Neptune.
In 1986 we saw mysterious Uranus for the first time (I remember watching that one on TV too!) – while the planet itself turned out to be a bit of a visual disappointment (just a bland greenish sphere), the moons proved to steal the show yet again, with Miranda’s crazy patchwork terrain and huge cliffs, Ariel’s rifts, and Titania’s canyons. Sadly the geometry of the flyby meant that we couldn’t get as much information as we did from the previous ones, since Uranus is tipped on its side and Voyager was passing through the system essentially at perpendicularly relative to the satellite orbits – so we had to be content with distant views of the other moons that could only hint at interesting features.
In 1989, as the Eastern Bloc was starting to crumble here on Earth, Voyager 2 flew past Neptune, revealing a blue world with high cirrus clouds casting shadows on the atmosphere below, a great dark spot, a super-fast “Scooter” bright spot, and clumpy rings. Again though, the satellite Triton stole the show, with its pink methane icecap, frozen nitrogen lakes, mysterious “cantaloupe terrain”, and cryovolcanic geysers that erupted dark material into the satellite’s incredibly thin atmosphere.
And finally, in 1990, Voyager 1 was commanded to perform one last task – to take a family portrait of the solar system from its vantage point about 40 AU from Earth. And there was Earth, a “pale blue dot” looking small and insignificant and almost lost in the glare of the sun. The late, great, Professor Carl Sagan summed it up nicely:
From this distant vantage point, the Earth might not seem of particular interest. But for us, it’s different. Consider again that dot. That’s here, that’s home, that’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam. – Prof. Carl Sagan.
And they’re still going today, barely. The signals from the Voyagers is getting weaker over time as their power runs low and the get further from Earth, but they’re probing the very edge of the sun’s influence and may reach interstellar space in the next few years. Voyager 2 just passed 13 light-hours from Earth, and Voyager 1 is just over 16 light-hours from Earth (over 115 AU!). The cameras may be dead but they’re still sending back good science with their other instruments about the solar wind out there at the edge of the solar system, and hopefully they’ll last till about 2025.
The spacecraft that we have sent out there since then – Cassini, New Horizons, and Galileo – are following in the metaphorical footsteps of Voyager, and those more long-term missions are answering many of the questions that Voyager raised (while raising more of their own, of course). But Voyager’s always going to have a special place in my heart because through that the outer solar system was revealed in all its glory to humanity for the first time, and in some way I was a part of that.