Cassini's Circus Trivia Quiz

Answer: Pan

Pan was discovered on July 16, 1990 by NASA Scientist Mark Showalter by analyzing images taken by Voyager 2. The small ravioli shaped moon is approximately 28 km (17 mi) in diameter. It is known as a shepherd moon and is one of the closest known moons to Saturn. The gravity of Pan sweeps up material from within Saturn's rings, creating the Encke Gap of Saturn's A-Ring.

Answer: Janus and Epimetheus

Janus and Epimetheus are two of Saturn's irregular shaped moons that were discovered in December, 1966. Janus is the larger of the two with an average diameter of approximately 180 km (112 mi). Epimetheus has an average diameter of 116 km (72 mi). Janus and Epimetheus have a unique interaction with one another. Every four years the two moons swap orbits around Saturn passing as close as 10,000 km (6,200 mi) to one another.

Answer: Mimas

Mimas was discovered by British astronomer William Herschel on September 17, 1789. The diameter of Mimas is approximately 396 km (246 mi). The most distinguishing feature of Mimas is a large impact crater discovered in 1980 by the Voyager spacecraft. The crater was named Herschel after Mimas' discoverer.

The Herschel crater causes Mimas to resemble the Death Star from "Star Wars". It is coincidental as the first "Star Wars" film was released in 1977, three years before the crater was discovered.

Answer: Enceladus

Enceladus was discovered by William Herschel on August 28, 1789. The moon is approximately 500 km (310 mi) in diameter. When the Voyager spacecraft flew by Saturn, Enceladus was not really studied in depth. However, when the Cassini spacecraft came to Saturn, it discovered active water-based geysers on the small moon. Enceladus is thought to have an underground mantle of liquid water, similar to the Jovian moon Europa.

This makes Enceladus a strong candidate for finding life on another world. The material ejected from Enceladus' geysers help form Saturn's E-Ring.

Answer: Trojan moons

Tethys (on the left) and Dione (on the right) were both discovered by Italian astronomer Giovanni Cassini (the man whom the spacecraft was named after) on March 21, 1684. They are very close in size to one another. Tethys, which is closer to Saturn, has a diameter of approximately 1,060 km (658 mi). Dione is slightly larger with a diameter of 1,120 km (696 mi). Both moons were discovered to have two Trojan moon companions (smaller irregular shaped moons that occupy the same orbit).

The moons Calypso and Telesto are the Trojan companions of Tethys and the moons Helene and Polydeuces are the Trojan companions of Dione.

Answer: Rhea

Rhea is the second largest moon of Saturn. It has a diameter of 1,527 km (949 mi). It was discovered by Giovanni Cassini on December 23, 1672. When the Cassini spacecraft observed Rhea, it was speculated that the moon might have a ring system of its own.

However, there was not enough data taken by Cassini to either confirm or deny that a ring system around Rhea currently exists. Astronomers might have to wait for a future mission to finally know for sure.

Answer: Hyperion

Hyperion was the first irregular shaped moon to be discovered in 1848. It is also one of the largest irregular shaped moons in the Solar System. It has an average diameter of approximately 270 km (168 mi). Neptune's moon, Proteus, is thought to be larger, but it's debatable.

Instead of rotating around a common axis, Hyperion seems to tumble around like a giant potato. This tumbling makes Hyperion's orbit very erratic.

Answer: Iapetus

Iapetus is Saturn's third largest moon and was discovered by Giovanni Cassini on October 25, 1671. It is only slightly smaller than Rhea with a diameter of approximately 1,468 km (912 mi). Iapetus has a few distinguishing features. The first is that the moon has a distinctive bright and dark hemisphere. Iapetus also features a 20 km (12 mi) tall ridge of mountains that stretch along the moon's equator. Iapetus is tidally locked to Saturn, which means only one side faces the planet throughout the moon's orbit.

Answer: Phoebe

Phoebe is one of the outermost moons of the planet Saturn. Its discovery was confirmed on March 17, 1899. Phoebe is an irregular shaped moon with an average diameter of 212 km (132 mi). It is believed that Phoebe may be a captured object that originated from the Kuiper Belt. Phoebe has a retrograde orbit that is inclined 152° compared to Saturn's equator. Phoebe was the first object encountered by the Cassini spacecraft as it approached Saturn in 2004.

Answer: Titan

Titan is the largest moon of Saturn and the second largest moon in the entire Solar System. It has a diameter of 5,148 km (3,199 mi). Titan was discovered on March 25, 1655 by Dutch astronomer Christiaan Huygens. Titan is the only moon in the Solar System known to have a thick atmosphere, like Earth's.

The atmosphere consists of mostly nitrogen. It is speculated that Titan may have liquid methane on its surface that forms lakes and rivers in the same way water does on Earth. The Huygens space probe was launched with Cassini in order to study the moon up close.

In 2004, it sent back stunning images as it descended through Titan's atmosphere.