Titans and Giants Trivia Quiz

Answer: Nitrogen

Where Earth's atmosphere is 78.1% nitrogen (and 20.1% oxygen), the atmosphere of Titan is 98.4% nitrogen. Titan is the only moon known to have a significant atmosphere. Its atmospheric pressure is actually greater than that of Earth's, and Titan's lower gravity means that the atmosphere extends out further than Earth's.

When Titan was first discovered, it was believed to be larger than Ganymede (one of the Galilean moons of Jupiter and the largest moon in the solar system), but the largely opaque atmosphere made observers believe it had a larger diameter than it actually did.

Titan is also unique among the moons of the solar system in that it has an active liquid cycle, with clouds, precipitation, lakes and rivers (of liquid methane).

As mentioned, Titan is very large as moons go, with a diameter of 5,152 km. It orbits beyond the E Ring at a distance of roughly 1,200,000 km from the center of the planet.

Answer: Giovanni Domenico Cassini

Iapetus is Saturn's third largest moon, and the eleventh largest in the solar system (fitting between Oberon of Uranus and Pluto's Charon). Its diameter is 1,469 km and it orbits much further out than Titan (the next major inward moon) at a distance of 3,560,820 km from the centre of Saturn.

Giovanni Domenico Cassini (1625-1712) observed Iapetus from the Paris Observatory, but could only see it when it was on Saturn's west side. He surmised that it was darker on one side than the other, a theory later proven with a more powerful telescope. The darker hemisphere was named Cassini Regio, in honour of its discoverer.

Answer: No

Saturn does have moons that travel in a retrograde direction, but Rhea is not one of them.

Rhea is part of the outer group of large moons, positioned beyond Saturn's E Ring (more than 480,000 km out from the centre of Saturn). Rhea is the first of these, then comes Titan, Hyperion and Iapetus. Rhea's orbital period and rotation period are synchronous at 4.518212 days, meaning that the same side of the moon is always facing Saturn.

Although Rhea is Saturn's second-largest moon, at 1,528 km in diameter it is still less than one third the size of Titan.

Answer: Sidera Lodoicea

Giovanni Domenico Cassini followed the example shown by Galileo when he named the Jovian moons that he discovered 'Sidera Medicea' after his patron. In this case, King Louis XIV was the patron of the Paris Observatory, of which Cassini was the Director, and the direct translation of Sidera Lodoicea is Louisian Stars.

Tethys was named for the Titaness and river goddess of Greek mythology. It has a diameter of 1,060 km and has two co-orbital moons (Telesto and Calypso, both discovered in 1980), called trojans or Lagrangian objects.

Dione was also named for a Titaness, the mother of Aphrodite. It has a diameter of 1,122 km and (like Tethys) also has two co-orbital moons (Helene, discovered in 1980 - and Polydeuces, discovered in 2004).

Both Tethys and Dione are within the E Ring, Tethys at approximately 295,000 km from the centre of the planet, and Dione at approximately 377,000 km.

Answer: Enceladus

Not only was Enceladus the sixth moon of Saturn to be discovered, it is also the sixth largest of Saturn's moons with a diameter of 504 km. It was the innermost of all of the moons discovered to that date, at approximately 238,000 km from the centre of the planet.

The Cassini spacecraft flew past Enceladus in 2005 and observed more than 100 geysers on the moon, near the south pole. It is surmised that these ejected materials have contributed to the formation of Saturn's E Ring.

Answer: Mimas

Interestingly, Mimas is in a 2:1 orbital resonance with Tethys in the same way that Enceledas is with Dione. In order (not counting smaller moons and moonlets), from inner to outer, are Mimas, Enceladus, Tethys, and Dione.

Mimas is also the satellite that is responsible for creating the Cassini Division - the space between Saturn's A Ring and B Ring.

With a diameter of 396 km, Mimas is Saturn's seventh-largest moon, and the 21st-largest in the solar system.

Answer: William Herschel

Sir Frederick William Herschel (1738-1822) did not become interested in astronomy until the age of 35, after which he became a pioneer in the field, constructing his own large telescopes, and developing sophisticated diagnostic tools for the observation of the cosmos.

At the time of the discovery of Enceladus and Mimas, Herschel was using his newly constructed 1.2 metre telescope, the largest in the world at that time.

Answer: Johann Gottfried Galle

The father-and-son team of William (father) and George (son) Bond discovered Hyperion on September 16th, 1848. Two days later, it was also independently discovered by William Lassell, who actually published his findings before the Bonds did. All three are given credit for Hyperion's discovery.

Hyperion is an interesting moon, looking very like a sponge, and having a very wobbly rotation. Its mean diameter is roughly 122 km, and its orbit falls between Titan and Iapetus.

Answer: It was discovered in a photograph.

A photographic plate of Saturn taken on August 16th 1898, from the Boyden Observatory in Peru, was the source of the discovery of Phoebe by Pickering, who didn't actually 'discover' it until March of 1899.

Phoebe (unlike Rhea) actually does have a retrograde orbit, meaning that it orbits Saturn in the opposite direction from Saturn's rotation. Phoebe is one of Saturn's outer moons, orbiting at a distance of nearly 13,000,000 km. It is an irregularly-shaped moon that has a mean diameter of about 220 km.

Answer: Cronus

Cronus (by whatever spelling) was the youngest of Uranus and Gaia's children - the first generation of Titans. His siblings were Rhea, Oceanus, Hyperion, Theia, Coeus, Phoebe, Iapetus, Crius, Mnemosyne, Tethys and Themis. Cronus also happened to be the father of Zeus, Hera, Poseidon, Hades, Hestia, Demeter, and Chiron.

Zeus, of course, overthrew his father in turn, casting him into Tartarus.

For a time, after the naming of the first seven of Saturn's moons, they were known as the Cronian moons.