NASA's Juno spacecraft performed its 42nd close pass by Jupiter on October 28, 2022, and as is routine, the spacecraft's Stellar Reference Unit (SRU)—a star-tracking camera that helps Juno maintain a stable orientation in space—collected a series of images of Jupiter. Citizen scientist Björn Jónsson processed the images into a stunning composite mosaic, and another citizen scientist, Kevin M. Gill, further processed the mosaic to reveal the changes that are taking place in Jupiter's atmosphere over time, particularly in the region of the planet's north pole, where the colossal polar cyclone resides.

The north polar cyclone is the largest storm in the Solar System, spanning about 1,400 miles (2,250 kilometers) in diameter. This swirling storm has been observed by Juno since the spacecraft arrived at Jupiter in July 2016. Over time, the storm's appearance and structure have changed, including the color and distribution of clouds within the cyclone.

To track these changes, Jónsson and Gill took advantage of Juno's unique vantage point, which allows the spacecraft to obtain close-up images of the planet's poles. The images used to create this mosaic were taken at an altitude of about 21,500 to 22,500 miles (34,600 to 36,200 kilometers) above Jupiter's cloud tops.

By comparing images of Jupiter's north pole taken during Juno's first nine science orbits (2016-2018) with images taken during orbits 29 to 42 (2021-2023), Jónsson and Gill noticed some subtle but significant changes in the appearance of the polar cyclone.

In the earlier images, the polar cyclone appeared mostly white and bright, with a hint of blue in the center. However, in the more recent images, the cyclone appears more varied in color, with shades of blue, purple, and red becoming more prominent. These color changes may indicate differences in the composition and distribution of clouds within the storm.

Additionally, the shape and structure of the cyclone seem to have evolved over time. The storm's central dark region, which is formed by the upwelling of gases from deep within Jupiter's atmosphere, has become more elongated and less circular in recent images. The bright "spokes" that extend outward from the cyclone have also become more prominent and less curved, suggesting changes in the dynamics and circulation of the storm.

These observed changes in Jupiter's north polar cyclone underscore the dynamic and ever-changing nature of the planet's atmosphere. By continuing to monitor Jupiter over time, Juno will provide scientists with valuable insights into the processes driving these atmospheric changes and deepen our understanding of the largest planet in our Solar System.