NASA’s Juno mission continues to snap pictures of Jupiter, which citizen scientists have been processing into absolute masterpieces. In the latest perijove, when the spacecraft is at its closest point to the planet, Juno captured the shadow of the volcanic Moon Io on the atmosphere of Jupiter.
On September 12, Io was blocking the Solar disk, casting its shadow on the colorful North Equatorial belt. Both Seán Doran and Kevin M. Gill shared beautiful views of the event, with a crisp silhouette of Io above the turbulent Jovian atmosphere.
When we look at solar eclipses from space, their contours are fuzzy (at least on Earth). The solar eclipse on Jupiter looks significantly different due to the systematic difference between the two systems. Our Moon looks roughly the same size as the Sun as seen from Earth, which allows for a less distinct shadow.
“Why is the Moon’s shadow on Earth fuzzy while Io’s shadow on Jupiter is so sharp? Io is so big & close that it more than blocks the Sun (it appears 4x as big as the Sun from Jupiter’s perspective) and it’s so close that the penumbra (fuzzy outer edge of shadow) is super thin,” astronomer Dr Katie Mack commented on a Twitter thread about the pictures.
The images were shot using JunoCam's instrument onboard the NASA spacecraft. The camera allows for views in visible light, with an incredible resolution of about 15 kilometers (9 miles) per pixel. The raw data is sent to Earth where people like Doran and Gill process it. Anyone can get involved through the JunoCam website. You can even suggest points of interest for future observations.
The spacecraft reached Jupiter in 2016. It performs a close flyby every 53 days with the next one happening on November 3, which will be the 23rd out of 35 planned flybys. The last one will take place on July 30, 2021, and will end in a controlled swan dive into the planet. This is to avoid any possible contamination of life-bearing worlds such as Jupiter’s moon Europa.