Jupiter’s volcanically active moon, Io casts its shadow on the planet in this spectacular image snapped by NASA’s Juno spacecraft. As with eclipses on Earth, within the dark circle that runs through the clouds of Jupiter, one would witness a complete eclipse when it passes in front of the Sun.
Such events tend to occur frequently on Jupiter because it is a really massive planet and it has many moons.
In addition, and unlike most other planets in our solar system, Jupiter’s axis is not very inclined in relation to its orbit, so the Sun never departs from the equatorial plane of Jupiter (+/- 3 degrees).
This means that Jupiter’s moons regularly cast their shadows on the planet throughout the year.
So, if you were actually on Jupiter, were that possible, you’d experience a series of stunning eclipses.
A stunning view
Juno’s proximity to Jupiter provides an exceptional fisheye view, which shows a small fraction near the planet’s equator. The shadow is approximately 3,600 kilometers wide, approximately the same width as Io, but it seems much larger in relation to Jupiter. That’s just a photographic misconception.
A little larger than Earth’s Moon, Io is perhaps most famous for its many active volcanoes, propelling material well above its thin atmosphere.
Amateur astronomer Kevin M. Gill created this enhanced-color image using data from the spacecraft’s JunoCam imager.
The raw image was taken on September 11 while the Juno spacecraft made its close overflight of Jupiter number 22. At the time the image was taken, the spacecraft was about 7,862 kilometers from the top of the clouds at a 21-degree latitude.
With a diameter of 3600 kilometers, it is the third largest of Jupiter’s moons.
On Io, there are very large plains and several mountain ranges, but the absence of impact craters speaks of the geological youth of its surface.
With more than 400 active volcanoes, it is the most geologically active object in the solar system.
Io is quite the unique moon. According to astronomers, unlike most of the solar system’s external satellites, which are covered with thick layers of ice, Io is mainly composed of silicate rock surrounding a core of molten iron.
Astronomers argue that Io most likely has a fine atmosphere composed of sulfur dioxide and some other gases.
Unlike the other Galilean satellites, it almost completely lacks water.
This is probably due to the fact that in the formation of the Galilean satellites, Jupiter was so hot that it did not allow the condensation of the most volatile elements in the region near the planet. However, volatiles condensed at distances much further out, giving rise to other satellites which show an abundant presence of ice.