It was over 400 years ago that Galileo Galilei first looked through his handmade telescope and observed the cloud bands that the planet is now famous for. The red gas giant of our solar system was revealed to be surrounded by swirling clouds, including one bright red spot–a cyclone of epic proportions that has been raging for millions of years.
Astronomers have since studied this planet from the ground and sent satellites whizzing past to take a closer look. These early images solidified the characterization of Jupiter as a planet of striped clouds in shades of red and orange. But we were missing a key part of the planet in our observations—the poles.
Looking at Earth from space, you see mostly blue water and the continents, surrounded by some white clouds. You might think everything was too warm to freeze, until you look at our north and south poles. There, it is ice-covered all year, nothing like the rest of the planet. Jupiter is the same way—the poles are unlike the rest of the planet.
The first hint of strange activity at the poles came from a Hubble Space telescope image of Jupiter. Below, we see a ring of excited particles creating a glowing aurora around the north pole. These glowing lights are similar to our northern lights, though they seem to be less colorful. This puzzled scientists who believed the entire planet to be swathed in bands of clouds, so they needed to take a closer look.
On July 4th, 2016, the Juno spacecraft entered Jupiter’s orbit. This mission was designed to study everything it could about the planet from planetary evolution to the magnetic fields, and also the poles. And with the end of the primary mission approaching in July 2018, a lot has been achieved. (Update: NASA has approved Juno to continue operating until July 2021 with a modified orbit.)
The first images of the north pole stunned astronomers. Eight circular storms surrounded one central storm, and it was about the same at the south pole, only with five storms. Not only were the multiple storms surprising—they weren’t even the hexagon shape seen on Saturn’s north pole—these circular storms were also stable. Although it seems odd to call a storm stable, this means that the storms were not changing in size or merging with each other like many other fluid systems.
Juno has since sent back data from the Jovian InfraRed Auroral Mapper (JIRAM) instrument and a 3-D flythrough of the storm is available. Because this camera looks in the infrared, we are able to peer 45 miles through the clouds and understand the temperature changes. In the visualization, the yellow areas are warm clouds, deeper in the atmosphere than the colder clouds seen in darker hues. Of course, this is hot and cold for Jupiter, where the range of temperatures is from -117° F (-83° C) to 9° F (-13° C), far colder than any winter here in Bloomington! These storms give detailed clues about the interior rotation of the planet and help give context to the study of Jupiter’s magnetic fields.
With Juno’s mission nearly over, it has spent two years collecting data on Jupiter. The spacecraft will dive into the atmosphere of Jupiter and burn up so it does not contaminate the planet. Juno has given us a wealth of information, but astronomers always want to know more. In addition to performing a more detailed analysis of the data, other missions to study Jupiter are approaching. Europa Clipper will be studying one of Jupiter’s moons to look for signs of life, Lucy will study the asteroids around Jupiter to learn about the formation of our solar system, and the European Space Agency will lead JUICE to study Jupiter’s icy moons in greater detail. All of these will be collaborations between multiple space agencies as we head into the future of planetary exploration together.
For more information on this early exploration of Jupiter, check out the Juno mission page!