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Jupiter, one of the four gas giants, is the largest planet in our solar system and accounts for more than twice as much mass as all the other planets combined. Although most people are only familiar with Saturn’s distinctive rings, all gas giants have planetary ring systems. Saturn’s characteristic rings are primarily composed of highly reflective ice, and for this reason, we can observe them from Earth using advanced telescopes. Jupiter’s rings, however, are mainly made of dust, making them difficult to see. Scientists have observed five sets of rings around Jupiter, including the main ring, halo ring, Amalthea Gossamer ring, Thebe Gossamer ring, and Himalia ring.
Although Jupiter is massive, it is made up of some of the lightest elements, including hydrogen and helium. Because the planet is a gas giant, it lacks a solid surface which prohibits spacecraft from landing on it. What makes Jupiter interesting is its short day and contrastingly long year. A day on Jupiter is approximately 10 hours long, however, it takes 12 Earth years for Jupiter to complete an orbit around the Sun.
Jupiter’s main ring is approximately 6,500 km wide and varies between 30 and 300 km in depth. The main ring is the brightest in Jupiter’s ring system due to its relatively low dust content. While Jupiter’s other rings are composed entirely of dust, the main ring has a dust content of about 25% and contains small quantities of ice, rocks, and other volatile materials. The age of the main ring is currently unknown, but it is thought to have originated because of collisions between the remnants of small moons orbiting Jupiter in the past. The main ring is bounded by the orbit of Adrastea, the second closest moon to Jupiter, which contributes particles to the ring as it collides with other bodies.
Jupiter’s halo ring is the thickest and closest ring to the planet. The halo ring is approximately 30,500 km wide and 12,500 km in depth, making it Jupiter’s vertically thickest ring. The halo ring lacks visible structure due to its composition, which mainly includes submicrometer dust. This delicate ring is thought to have been derived from Jupiter’s main ring, leading scientists to hypothesize that they are very close in age.
The Amalthea Gossamer ring is among the faintest of Jupiter’s rings because it is comprised of dust roughly the size of smoke particles. This ring extends from the orbit of Amalthea, one of Jupiter’s moons, and is approximately 53,000 km wide and 2,000 km in depth. This ring is thought to have been formed by a series of successive collisions between Amalthea and several small, discrete bodies detected by the Galileo spacecraft.
The Thebe Gossamer ring is the faintest in Jupiter’s ring system and extends from the orbit of Thebe, the fourth closest moon to Jupiter. This ring is three times fainter than the Amalthea Gossamer Ring and additionally extends beyond the orbit of Thebe, making it the widest of Jupiter’s rings at approximately 97,000 km. This ring is about 8,400 km in depth and has nearly the same total mass as the Amalthea ring.
The Himalia ring is the most recently discovered of Jupiter’s rings and was first photographed by NASA’s New Horizons spacecraft in September 2006. As the spacecraft approached Jupiter for a gravity assist, it discovered a ring arc parallel with the orbit of Himalia, the largest irregular moon of Jupiter. Scientists believe that this ring formed relatively recently due to a collision between Himalia and a small, undiscovered moon. Although not much is known about the Himalia ring, its discovery suggested that Jupiter gains and loses small moons and rings over time.
Jupiter’s rings were first discovered by NASA’s Voyager 1 space probe in 1979 as it made its journey to interplanetary space. Because Jupiter’s rings are so faint and delicate, they only became visible once the spacecraft passed the planet and looked back to see them illuminated by the sun. Follow-up missions to Jupiter were able to image Jupiter’s rings using infrared light, which revealed their faint and glowing signature.
NASA’s Voyager 2 space probe conducted more extensive imaging of Jupiter’s rings, allowing scientists to roughly determine their structure. This discovery prompted the initial plans for Galileo, a space probe and orbiter that studied Jupiter and its moons extensively between 1995 and 2003. Galileo captured superior images of Jupiter and its rings, which vastly expanded upon the existing but limited knowledge about them. Following Galileo, the Cassini spacecraft conducted extensive observations of Jupiter’s ring system in 2000 during its journey to Saturn.
On top of ground-based observations conducted by advanced telescopes, images of Jupiter’s rings were additionally transmitted by the New Horizons spacecraft in 2007. These images allowed scientists to observe the fine structure of Jupiter’s main ring for the first time. The most recent mission to Jupiter was carried out by NASA’s Juno spacecraft, which arrived at the planet in 2016. This spacecraft’s goal is to understand the origin and evolution of Jupiter, map its magnetic field, observe its auroras, and measure the quantities of elements deep in its atmosphere. Juno transmits valuable data to engineers and scientists to this day and is on the leading edge of Jovian exploration.
Although several spacecraft have contributed to the discovery and knowledge of Jupiter’s rings, many more missions have been planned. These include the European Space Agency’s “Jupiter Icy Moons Explorer” (JUICE) and NASA’s Europa Clipper, which are both set to launch in the mid-2020s. Both orbiters will conduct in-depth observations of Jupiter and its moons using advanced and sensitive instruments. Not only will these spacecraft provide scientists with more information about Jupiter’s rings, but they might also aid in unlocking the secrets behind their origins.
Featured Image Credit: GustavoAckles, Pixabay
Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.
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