In the early 1880s, the French astronomer Étienne Léopold Trouvelot published a dreamy illustration of Jupiter based on his telescope observations. Back then, the gas giant looked, through telescopes, like a fuzzy, gray marble, a dust particle hanging in the night sky. Trouvelot, who in his life created 7,000 astronomical drawings, sought to add a little more detail to the picture to enhance the planet’s features.
“My intent is ... to represent the celestial phenomena as they appear to the trained eye and to an experienced draughtsman through the great modern telescopes provided with the most delicate appliances,” he wrote at the time. He drew, with distinct lines and colors, Jupiter’s bands of swirling clouds and its trademark blotch, the Great Red Spot. “My aim is to combine ... accuracy in details ... with the natural elegance and delicate outlines peculiar to the objects depicted,” he explained.
More than a century later, the desire to share Jupiter with the public in this way lives on. Since July of last year, NASA’s Juno spacecraft orbiting Jupiter has returned batch after batch of grainy, raw images. When a new set arrives, the images are quickly uploaded to a public website, where a band of space enthusiasts, sprinkled around the world, grab them and get to work. They stitch the images together, make a few color corrections, and start sprucing. Some adjustments to contrast here, a little brightening there. They try to show Jupiter as Trouvelot did—the planet as it is, yes, but also as it is if humanity could get even closer, peer a little deeper, and see the wondrous details of a neighbor in the solar system.
The process has led to a trove of stunning photos of Jupiter, unlike anything other space missions have ever produced. The detail is stunning. Zoomed in, Jupiter’s clouds look like cream swirling in coffee, or like the textured brushstrokes of a Van Gogh. They look like art.
Some of the amateur processors behind these pictures hang out on Unmanned Spaceflight, a no-frills internet forum where users can share and discuss spacecraft imagery. “It’s time to start a new topic for Juno’s Perijove-09,” wrote Gerald Eichstädt in a post on the forum last week. Eichstädt is a mathematician who works in software and lives in Stuttgart, Germany. Juno had recently completed its ninth flyby of Jupiter—a close approach known as a perijove—and Eichstädt was waiting for the pictures to show up online. Juno returns photos about every 53 days, thanks to an elongated orbit that brings the spacecraft toward the planet for a few hours before flinging it back out.
“More power to you Gerald,” wrote back Seán Doran, a designer in London. “Next week is going to be busy and fun!”
Doran wished his fellow image processor luck because translating data from Juno’s camera into something usable is no easy feat. JunoCam, as it’s called, doesn’t take pictures like the camera on a smartphone, or even like the camera on other spacecraft. It photographs in hundreds and hundreds of narrow strips through red, green, and blue filters—all while spinning around about every 30 seconds. These strips, called framelets, have to be arranged and stitched together to create coherent, composite photographs.
While Juno cruised to Jupiter, Eichstädt developed a computer program that automates this assembly, and he’s still tweaking it today. When a fresh batch of pictures becomes available, Eichstädt dumps the raw images into the program and lets it run. When that’s done, he shares the composite images with his fellow processors, and everyone jumps over to Photoshop to tinker with the images, produce their own takes, and create animations.
Their final photos, shared widely on social media, transform Jupiter from an abstract, distant planet into a dynamic world swirling with stormy weather. “You can see the clouds—that’s something we can wrap our minds around,” Doran said. “All of a sudden, the planet becomes real.”
The adjustments make the colors of Jupiter—all kinds of shades of orange and red and blue—pop. Without tinkering, Jupiter would look muted. For example, here’s a true-color version, from Björn Jónsson, a software engineer in Iceland who has also processed images from the Cassini, Galileo, and Voyager missions.
Most processed photos are usually not “true color” images of Jupiter—but that’s not a bad thing.
“I’m not looking for ‘true/natural color’ in my images, because enhanced color can show us a little more,” explains Roman Tkachenko, an amateur astronomer and music producer in Kursk, Russia. Tkachenko assembles the many raw images manually before taking a Photoshop brush to them. “I just want to show people something more than they can see in unprocessed images,” he said.
Doran agrees. “It’s like peeling back a curtain,” he said. “You just want to reveal what’s there. That’s what motivates me—and I try not to upset the scientists too much.”
The people behind the Juno mission see it that way, too. Candy Hansen, a senior scientist at the Planetary Science Institute who leads the JunoCam team, said using artificial hues makes features in Jupiter’s atmosphere stand out. “We don’t turn up our noses at artificial color,” Hansen told me for an earlier story about JunoCam’s photos. “We love artificial color.”
The Juno mission doesn’t have a dedicated staff to process raw images from JunoCam, and usually relies on the group of processors to produce photos—for free—to share with the public and include in press materials. JunoCam wasn’t designed for scientific purposes—its sole mission is, quite literally, to take pretty pictures—but the Juno team has used the images to better understand the meteorology of gas giants, in our solar system and beyond. “Jupiter can be considered as representing a population of gas giants, likely a widespread population of celestial bodies in the observable universe,” Eichstädt said. “Understanding Jupiter means understanding non-negligible portions of our universe.”
The first rule of Juno club is that image processors be up-front about the changes they make, said Emily Lakdawalla, an editor and scientist at The Planetary Society and one of the administrators of Unmanned Spaceflight. “You need to be very clear about what you’ve done in order to create the image so you aren’t saying it’s a true representation.”
The Juno processors seem like a supportive and collaborative bunch, even though they’ve never met. There’s a hint of competition, but that’s to be expected in a community of artists, said Jason Major, a graphic designer in Rhode Island. “It’s a very friendly competition—who finds what interesting feature, who can work the quickest, who can get the best result.”
Major said they’ve been at this for enough time that it’s possible to guess which processor produced a particular Juno picture. “Everybody has their own eye, their own aesthetic sense as far as what looks good, and that’s what makes it interesting,” he said. “If you were to send 10 photographers out into the world and have them come back a day later and show you their results, you’re going to be seeing very, very different things.”
Take, for example, processed photos of the Great Red Spot, a storm that has been raging perhaps for centuries. Juno came within 5,600 miles of the spot in July, closer than any spacecraft before it. The raw images from that flyby were some of the most exciting shots the Juno processors had seen, and they raced to process and post them online. The depictions, each of them certainly dazzling, varied. The color of Major’s Great Red Spot turned out a soft orange, while Eichstädt’s was a fierce red.
The image processors have a few more weeks until the next perijove in December. The flyby will produce, again, hundreds and hundreds of strips ready for stitching, but they won’t look the same as last time. In fact, no photo of Jupiter, raw or processed, can ever look the same. The planet’s storms are always brewing, always shifting. A gorgeous filigree of clouds captured during one flyby may be gone in the next.
“Jupiter's clouds are constantly changing,” Jonsson said. “Each day it looks in some way at least slightly different from what it has ever done before.”