Moons Trivia Quiz

Callisto is the second largest moon of Jupiter and is one of the four moons discovered by Galileo Galilei in 1610, along with Io, Europa and Ganymede. Callisto has a diameter of approximately 4,800 km (3,000 mi) and has the outermost orbit of the four Galilean moons, orbiting Jupiter once every 17 days.

Callisto, which is heavily cratered, is the only Galilean moon that is not believed to be geologically active. Callisto was named after a nymph from Greek mythology who was believed to be one of the many lovers of Zeus (Greek counterpart of Jupiter). The image of Callisto was taken by the Galileo spacecraft in 2001.

Umbriel is one of two Uranian moons discovered by English astronomer William Lassell on October 24, 1851. It is the third largest moon of Uranus behind Titania and Oberon with a diameter of 1,170 km (727 mi). Umbriel takes approximately four days to orbit its parent planet.

While the majority of Uranian moons were named after Shakespearean characters, Umbriel's name comes from a "dark sprite" featured in the poem "The Rape of the Lock" by Alexander Pope. It seems to be a fitting name due to the moon's distinctive dark surface. The image of Umbriel was taken during Voyager 2's fly-by of Uranus in 1986.

Triton is the largest moon of the planet Neptune. It has a diameter of approximately 2,700 km (1,680 mi) and takes 5.9 days to orbit its parent. Triton was first discovered by William Lassell on October 10, 1846. The moon was given the name Triton, who was the mythological son of Poseidon (Greek counterpart of Neptune).

Triton is a rather unusual moon. Firstly, it is geologically active. However, instead of traditional volcanoes, Triton has cryo-volcanoes which spew nitrogen based substances onto its surface. In addition, Triton is the only moon of its size to a have a retrograde orbit around its parent planet, meaning that it orbits in the opposite direction. It is believed that Triton may not be a natural satellite of Neptune, but rather a wandering Kuiper Belt object that was captured by Neptune's gravity. The image of Triton was taken during Voyager 2's fly-by of Neptune in 1989.

Enceladus is one of the many moons of Saturn. It was first discovered by Sir William Herschel on August 28, 1789. It is a relatively small spherical moon with a diameter of approximately 500 km (310 mi). It takes roughly 33 hours for Enceladus to orbit Saturn. Enceladus was named after one of the giants from Greek mythology. Despite being a small moon, Enceladus has become a giant in its scientific potential.

When the Cassini spacecraft (from which the photograph was taken) visited the Saturnian system, it discovered that Enceladus featured numerous geysers that spewed water vapor among other substances. It is believed that a liquid water ocean may lie deep under the moon's crust (similar to Europa). The material ejected from Enceladus forms Saturn's E ring. This makes Enceladus a strong candidate for discovering life on another world.

Io is the third largest and the innermost of Jupiter's Galilean moons. It has a diameter of approximately 3,640 km (2,260 mi) and orbits Jupiter once every 42 hours. Io is one of the most geologically active bodies in the entire Solar System with active sulfuric volcanoes covering its surface.

The constant eruptions on Io cause it to resemble a giant pizza when viewed through a telescope. Io's volcanic activity is caused by tidal forces that the moon experiences due to its close proximity to Jupiter as well as the other three Galilean moons (Europa, Ganymede and Callisto). Io was named after one of Zeus' mortal lovers from Greek mythology. The image of Io was taken by the Galileo spacecraft in 1999.

Charon is the largest moon of the dwarf planet Pluto. It has a diameter of approximately 1,210 km (752 mi), which is nearly half that of its parent. In fact, Charon does not orbit Pluto, but around a common center of gravity (barycenter) between the two bodies. It takes Charon roughly six and a half days to complete one orbit around the Plutonian barycenter.

Charon was discovered by American astronomer James W. Christy on June 22, 1978. Its name comes from the ferryman of the underworld in Greek mythology, who is associated with the god Hades (Pluto's Greek counterpart). Images of Charon and Pluto were taken during the New Horizons mission in 2015, which provided the first close up look at the dwarf planet and its moons since its discovery in 1930.

Ariel is the second of the twin Uranian moons that were discovered by William Lassell on October 24, 1851. It is the fourth largest moon of Uranus, only slightly smaller than its twin Umbriel, with a diameter of approximately 1,160 km (720 mi). Ariel orbits closer to Uranus than Umbriel does. It only takes Ariel two and a half days to orbit Uranus.

As with Umbriel, Ariel was also given the name of a character found in Alexander Pope's poem "The Rape of the Lock". Ariel is often considered to be the brightest moon of the Uranian system, opposite of its twin Umbriel which is often considered to be the darkest. The image of Ariel was also taken during Voyager 2's fly-by of Uranus in 1986.

Europa is the smallest and second closest of Jupiter's Galilean moons. It has a diameter of 3,100 km (1,940 mi) and orbits Jupiter once every 3.5 days. Europa was named for yet another of Zeus' mortal lovers from Greek mythology, after whom the continent of Europe on Earth was also named.

The same tidal forces that act on Io affect Europa as well, albeit to a lesser degree. Rather than having a volcanic surface like Io, Europa is believed to have an ocean of liquid water underneath its icy crust, which makes the moon another strong candidate for discovering extra-terrestrial life. The image of Europa was taken by the Galileo spacecraft in 1996.

Iapetus is another one of Saturn's moons. It was discovered by Italian astronomer Giovanni Cassini on October 25, 1671. Iapetus has a diameter of approximately 1,470 km (913 mi) and orbits Saturn once every 79 days. Iapetus was named after the Titan god of mortality from Greek mythology.

Iapetus has several distinguishing surface features. It is mostly known for having a distinctive bright side and dark side. In addition, Iapetus has a 20 km (12 mi) high ridge of mountains that wrap around its equator. The image of Iapetus was taken by the Cassini spacecraft (named for the moon's discoverer) in 2007.

Mimas is another small spherical moon belonging to the planet Saturn. It was discovered by Sir William Herschel on September 17, 1789. Mimas has a diameter of approximately 400 km (250 mi) and takes roughly 23 hours to complete its orbit around Saturn. Like Enceladus, Mimas was also named after one of the giants from Greek mythology.

One of the most distinguishing features of Mimas is a large crater named Herschel (named after the moon's discoverer) which causes it to resemble the Death Star from "Star Wars". The moon's resemblance to the Death Star is coincidental since the Herschel crater was not discovered until 1980, three years after the release of the first "Star Wars" film. The image of Mimas was taken by the Cassini spacecraft in 2010.