The Views of Jupiter You Won't Find in a Textbook
NASA spacecraft Juno is providing a fresh look at the gas giant since settling into its orbit last summer.
Imagine Jupiter as it’s usually depicted: a bulbous marble, with alternating bands of reds, oranges, yellows, and creams, a few wisps of blue and green, and that unmistakable round spot just south of the equator, the mark of a storm that has churned for decades.
This sideways view of Jupiter is the one humans have been used to seeing for decades, since the first close-up photos of the gas giant were taken by spacecraft in the 1970s. It’s also the only kind of view that spacecraft have really been able to get. Galileo, the orbiter that spent eight years studying Jupiter and its moons, traveled around the planet’s equator. Spacecraft like Cassini and New Horizons, on their way to other parts of the solar system, snapped sideways shots as they passed.
But not Juno. Juno has been circling Jupiter since last July, studying the planet’s composition and atmosphere, and took this photo earlier this month. It follows an elliptical polar orbit, which brings it close to Jupiter’s poles before flinging it way out to Callisto, one of the planet’s moons. Juno spends only a few hours at the poles, but it’s there that the spacecraft’s camera, the JunoCam, captured high-resolution, never-before-seen views of the largest planet in our solar system, the kind textbooks haven’t yet seen—like this one of Jupiter’s south pole.
“Even with the best possible telescope, you’ll never get a perspective like this from the earth,” says Candice Hansen, a senior scientist at the Planetary Science Institute who leads the JunoCam team.
So, what are we looking at?
“You’re basically looking at storms in an atmosphere,” Hansen says. Storms, like the Giant Red Spot, are Jupiter’s specialty. Winds blow at several hundred miles an hour all over the planet, and single storms can grow to be the size of an entire Earth. In this photo, each white orb is an individual storm. The swirling filigree of blue and cream hues, which Hansen says reminds her of her grandmother’s crochet patterns, are clouds. Jupiter has rotated away from the sun, shrouding the rest of the pole in darkness. The photo is not a true-color image, Hansen says, but it’s quite accurate.
The image was taken earlier this month during Juno’s fourth transit of Jupiter’s poles. The inaugural transit, in August, captured the first-ever images of the planet’s north pole, with its own swirling cloud tops and spherical storms. Juno, was forced to power down during its second transit in October because of potential mechanical problems, so no photos or measurements were recorded. The third trip in December yielded photos of Jupiter’s south pole like this one, but Hansen says the February transit produced the best views yet. The Juno mission posts JunoCam’s raw images online, where users can download and refine them with image-processing software.
Juno’s special orbit is useful for more than just capturing pretty pictures. Jupiter is surrounded by a giant magnetic field, where highly charged particles create radiation belts—bad news for anything trying to orbit the planet. But the radiation is weakest at the poles, so Juno can makes its close approaches without getting fried. It also helps that its computer and most of its scientific instruments sit inside a 400-pound titanium vault that reduces the radiation exposure by about 800 times.
Juno is scheduled to make its next stop by the poles next month, the first batch of more than 30 over its 20-month mission. Don’t expect the photos from that run to look like this one. Jupiter’s atmosphere is difficult to photograph for the same reason a puppy is: It doesn’t stay still. Storms shrink and expand, winds carve clouds into new, intricate arrangements. These changes are what help scientists like Hansen better understand the planet’s meteorology. Last week, Hansen and her team looked at this photo and started writing equations on a whiteboard to try to learn more about the meteorology of Jupiter’s poles. With each pass, Juno is not only providing more pretty pictures, but important information about how weather works on other planets, too.