On Voyager’s 40th anniversary, here are 20 of the mission’s best images and discoveries

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On Voyager’s 40th anniversary, here are 20 of the mission’s best images and discoveries

It’s been 40 years to the day since the Voyager mission commenced with the launch of Voyager 1 on September 5, 1977, with its twin Voyager 2 launching two weeks later. This groundbreaking and incredibly ambitious mission touched on practically every aspect of our solar system and planetary neighbors.

Here are 20 of the most important images and bits of science sent back by the pioneering spacecraft. As a rule, the images are from NASA/JPL, but they were collected from numerous sources, including Wikimedia Commons (where some high-resolution files are hosted) and the Space Science Data Coordinated Archive. If you want to learn more, NASA and JPL have you covered.


1. It pays to hedge your bets (but also bet big)

Voyager was born when it was observed that several planets would be aligning in a very convenient fashion in the late ’70s — a once-in-several-lifetimes opportunity to visit them all in one trip.

Or two, as it turns out. Because it would be difficult and expensive to carry out a trajectory that hit all targets perfectly (not to mention if something went wrong, they were sunk), NASA decided to send two identical craft, one after the other. The first would get close-ups of Jupiter and Saturn, while the second would get a different angle on them and hopefully head on toward Uranus and Neptune.

Everything — well, mostly everything — worked out as planned, and Voyager has been one of the most productive and surprising missions ever undertaken in space.


2. Ambition is human

As long as you’re sending something into interstellar space, why not prepare it for the possibility of extraterrestrial interception? “Moonshot” doesn’t adequately describe the ambition of the Golden Record project and the astronomically small odds of it ever being encountered by intelligent life, but that isn’t really the point.

The record and Voyager have inspired generations with the idea that it’s worth it to explore and try things just because we can, and because it’s part of our makeup. The very human contents of the Golden Record were curated by Carl Sagan, among the most humanitarian of scientists. The idea that our unique presence, from our biology to our ideas of beauty and philosophy, is blasting through outer space is awe-inspiring.


3. Jupiter is a cosmic storm

Voyager 1’s approach to Jupiter in early March of 1979 allowed scientists to see the planet in unprecedented detail both spatially and temporally — that is, in high resolution and with many images taken close together in time.

The first imagery showed that the planet and particularly its famous red spot are a chaos of fluid interactions, enormous storms that have raged for billions of years. The question of which direction the red spot spins was finally settled, as well, along with probably quite a few bets. (It’s counter-clockwise.)


4. Jupiter's moons are a fascinating menagerie

This image is a composite, but they’re all images of moons taken by Voyager 1.

Europa (center) attracted attention, especially after the second pass by Voyager 2, for the superficiality of its surface features. It’s the smoothest object in the solar system.

Callisto (lower left) was found to be old and cratered, and Ganymede (lower right), determined to be the largest moon in the solar system, showed signs of active tectonic processes.

But it was Io that stunned everyone.


5. Io blows minds

Images of Io showed enormous plumes extending nearly 200 miles above the surface: volcanoes, the first we’d encountered outside of Earth.

Subsequent research found that Io likely is volcanic due to being pushed around by Europa and Ganymede, producing tides of subsurface sulfur, oxygen and sodium that spew out at up to a kilometer per second. It’s been doing this for a long time, filling the space around Jupiter with matter and contributing to another new phenomenon observed in passing…


6. Jupiter has a near-invisible ring

A narrow, faint ring of dust can be observed if you look closely, and boy did Voyager look closely. A planet’s rings are important hints to its past, but first you have to find them. You can just see it, the orange lines on the left side of this picture. Later imagery showed it much more prominently when backlit by the sun.


7. Saturn is quietly complicated

Saturn’s more subtle markings suggested a calmer planet than Jupiter, and in a way, that’s true — but Voyager 2’s radio probing revealed complex patterns of jet streams suggesting that the currents of helium and hydrogen may extend deep within the planet’s gaseous surface. Voyager 1 approached Saturn in November of 1980, with 2 following in August of 1981.


8. Saturn's rings are full of insight and mystery

While from a distance and in the visible spectrum Saturn’s rings may look largely homogeneous, the Voyagers found that was very far from the case. Close inspection of the rings found dozens of distinct layers corresponding to different kinds and periods of formation. A history of Saturn’s moons and satellites is written in dust here.

Not only that, but they aren’t just a bunch of circles: there are spokes, wobbles and other variations, some of which is caused by slightly sloppy “shepherding” by the moons Pandora and Prometheus.

Some spokes, however, appeared and disappeared while Voyager watched — and no one knows why.


9. Titan is covered in primordial soup

Titan was of particular interest to Voyager’s scientists: it was known to have a substantial atmosphere, and Voyager 1 took a closer look than Pioneer had had a chance to.

It turned out that Titan has a thick layer of complex hydrocarbons like ethane, which may even form lakes on the surface. This kind of organic soup could be like that found on Earth before life emerged here. Of course, the -292 degree weather on Titan isn’t as inviting.


10. Saturn looks good from this angle too

Okay, this one is basically just a cool picture. As Voyager 1 was on its way out (its trajectory after Saturn took it away from the ecliptic and other planets) it snapped this sunward shot of Saturn. Beautiful, right?


11. Uranus is tilted in more ways than one

Voyager 2, with its different trajectory, approached Uranus in January of 1986. Unprecedented observations were made of the planet, which is “tilted” — the axis around which it spins is parallel to the ecliptic, rather than perpendicular. Imagine if Earth were hurtling around the sun with the North pole head first.

What scientists didn’t know, however, is that the magnetic field of Uranus is tilted in a different way, 60 degrees away from the physical tilt. This means that its “magnetotail” forms a sort of corkscrew shape on the night side of the planet. It’s complicated, but trust me, it’s cool.


12. Moons! Moons everywhere!

Another photo montage shows the five moons we knew Uranus had: Ariel, Miranda, Titania, Oberon and Umbriel, from largest to smallest.

But Voyager 2 also found not one, not two but 10 previously unknown moons around the planet. Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Perdita and Puck. It’s a good thing Shakespeare had so many characters in his plays.


13. Miranda is deeply weird

The first close inspection of the moon Miranda shows it to be so irregular that it seems like a cosmic mistake. It has enormous canyons 12 miles deep that follow strange patterns, but also areas totally undisturbed for likely millions of years.

It’s thought that perhaps Miranda was partly destroyed by some ancient impact, and reformed in this unsightly shape. The moon is unlike anything else in the solar system.


14. Neptune's surface is suprisingly variable

On approach to Neptune in August of 1989, Voyager 2’s observations showed that the planet is far from the static blue orb it appeared to be, and which its inner neighbor Uranus is.

Neptune has all kinds of surface features, including one observed for the first time by Voyager 2 called the Great Dark Spot. About the size of Earth, it appeared to be a large hole in the cloud cover produced by the shifting, multilayered atmosphere. As you can see, other clouds sit, move and cast shadows, creating a surprisingly Earth-like tableau, 30 times farther out from the sun.


15. The windiest place in the solar system and the "scooter"

Watching the surface showed that Neptune easily sports the solar system’s strongest winds. Near the Great Dark Spot, they reached 1,200 miles per hour.

Below the dark spot in this picture is a bright white one, which was observed “scooting” around the planet every 16 hours, around the same duration as a Neptunian day. They call it the scooter, naturally.

Below that is “Dark Spot 2,” which looks like an eye and probably should have been named better.

It doesn’t matter, though, since they’ve all disappeared since then.


16. Triton gets a close-up and a new history

The trajectory calculated by Voyager 2’s engineers used Neptune’s gravity to send the craft within spitting distance of the moon Titan, which was revealed in incredible detail.

The complexly textured surface suggests a rich geological past, and it’s covered in geysers shooting nitrogen and dust into space. Triton’s odd orbit also tells us it was not always a moon of Neptune, but at some point was captured and may have melted from the forces involved.

Titan is also the coldest place in the solar system, reaching 38 Kelvin, or -391 degrees Fahrenheit.


17. Farewell, ecliptic

The detour to Triton took Voyager 2, like its predecessor, away from the ecliptic, after which point they both flew inexorably toward the edge of the solar system.

This parting shot of Neptune is particularly beautiful, I think, though not particularly noteworthy in scientific terms.


18. Planetary self-portrait

Feel like a planet is missing from the lineup here? Oh yeah, Earth!

This portrait of the planet is the first time a spacecraft has looked back to see both Earth and Moon together, and it was on September 18, 1977, just two weeks after Voyager 1’s launch.


19. Pale Blue Dot

One of the most humbling images ever taken, the “Pale Blue Dot” is the Earth in the image, only a tenth of a pixel wide as part of an enormous panorama of the solar system taken by Voyager 1 on June 6, 1990.

At that point Voyager was far enough away from the ecliptic that it could see all the planets from “above.” It’s hard to imagine a better demonstration of cosmic scale. Carl Sagan sure thought so.


20. Into the black

More than 30 years after leaving Earth, Voyager 1 became the first spacecraft to enter interstellar space. Although there was some debate over when exactly this happened, researchers generally agree that it was in August of 2012 that the craft exited the heliosphere, the area where the sun’s radiation is the dominant force.

Since then Voyager 1 has been the first and only source for information on what it’s like outside the tiny bubble in which our planet and everything on it has been restricted to for all its billions of years.

That study will continue until sometime probably in 2025, when its radioactive power source will have decayed past a usable state. It will, however, continue to fly outwards toward the rest of the universe — and remember, that Golden Record doesn’t need power to function.