Ganymede: a Mighty Moon Trivia Quiz

Answer: Galileo Galilei

Galileo, using an early telescope, observed a set of heavenly bodies near Jupiter in 1609/1610 and thought they were fixed stars. After observing them for several days, he realized were not fixed stars, but instead were in orbit around Jupiter. He initially named them the Cosmian Stars or Medician Stars, in honor of Cosimo de Medici, ruler of Tuscany. Over time, the suggestion of Simon Marius and Johannes Kepler to name them after some of the lovers of Jupiter, King of the Roman gods, would take hold.

The four moons would be called Ganymede, Europa, Io, and Callisto. Ganymede was a beautiful mortal whom Jupiter claimed to serve as his cupbearer. He would grant Ganymede eternal youth and immortality. Galileo Galilei (1564-1642), in addition to his extensive work in astronomy, also made contributions to engineering and physics.

Answer: Mercury

Ganymede has a diameter of 3,273 miles. (By comparison, the distance from Seattle to Miami is 3,318 miles.) Mercury is slightly smaller with a diameter of 3,032 miles. The diameter of Mars is 4,212 miles. Interestingly, though Mercury is smaller in terms of diameter, because of differing composition, it is approximately twice as massive as Ganymede. In comparison to many of the smaller moons of Jupiter, Ganymede is large enough, and massive enough, to have a roughly spherical shape.

From 1930 to 2005, we would have had to add Pluto to the list of planets smaller than Ganymede. Though it is currently classed as a dwarf planet, Pluto is significantly smaller than Ganymede, with a diameter of 1,477 miles.

Answer: Io, Europa, Ganymede, Callisto

Ganymede has a mean distance of 665,100 miles from Jupiter. By comparison, Io is about 262,000 miles from Jupiter on average, Europa is about 416,900 miles, and Callisto is about 1,161,300 miles. Ganymede orbits Jupiter in about seven days, three hours. Because Jupiter and Ganymede are tidally locked, the same side of Ganymede always faces Jupiter. Europa orbits twice in the time it takes Ganymede to orbit once and Io orbits four times. Callisto's orbit is more than twice as long as Ganymede's at about 16 days, 17 hours.

Ganymede travels in its orbit at about 6.7 miles/second. Its orbit is relatively regular with an eccentricity of 0.0013.

Answer: Moon

The simplest way to answer this question is to compare the weight of the same individual in different locations. A person who weighed 100 pounds on Earth would weigh about 14.6 pounds on Ganymede. The same person would weigh about 16.5 pounds on the Moon, about 37.9 pounds on Mars, and about 2.9 pounds on the asteroid/dwarf planet Ceres.

Interestingly, the Moon has a slightly higher gravity than Ceres, even though Ganymede has a mass about twice than that of the Moon. This is due to Ganymede having a much lower density.

Answer: Water is very common on Ganymede

It is believed that there is a substantial amount of water on Ganymede, both on the surface and also in the form of an ocean below ground. The problem for human visitors would be that the water on Ganymede is almost entirely in the form of ice. With the typical range of surface temperature on Ganymede varying between about -333 degrees Fahrenheit and -186 degrees Fahrenheit, an additional heat source would be needed to bring the ice up to 32 degrees Fahrenheit so that it could melt.

It is possible that the ocean below the surface is liquid as temperatures there may be warmer.

Answer: Iron

The iron-nickel core of Ganymede is believed to be at a temperature of about 2200-2600 degrees Fahrenheit. The core is likely to be liquid because of the high temperature and despite the higher level of pressure. Surrounding the iron-nickel core is a rocky mantle and then the interior ocean and surface.

It is believed that the presence of iron produces a magnetic field around Ganymede. This magnetic field would largely be masked from a distance by Jupiter's own magnetic field.

Answer: Yes

The oxygen is probably released by solar radiation breaking the surface ice apart into hydrogen and oxygen. By comparison with the Earth, the atmosphere on Ganymede is very thin, roughly equivalent to Earth's exosphere (or outermost layer of atmosphere). Multiple forms of oxygen are found in Ganymede's atmosphere including O2 and O3 (ozone).

Answer: Its mass is less than that of either

The mass of Ganymede is about 1.4819 times 10 to the 23rd power kilograms. This is about 1/40 that of Earth and about half of Mercury's mass. Despite being significantly bigger than Mercury, the large amount of water on Ganymede gives the moon a lower average density. Mars, by comparison, has a mass about four times that of Ganymede.

Answer: Galileo

The Jupiter Orbiter Probe launched by the Galileo spacecraft performed several flybys of the four large moons of Jupiter as well as one flyby of the smaller moon of Amalthea. The primary mission of the probe lasted from 1989 to 1997 with extended missions lasting until 2003. The probe was purposely sent on a one-way trip into Jupiter's atmosphere in 2003 to prevent any bacteria on the probe from contaminating the moons. The probe was able to observe Ganymede's magnetic field.

The Magellan probe was sent to Venus. The Viking mission was sent to Mars. The Cassini probe was sent to Saturn.

Answer: Ganymede's craters are less pronounced

It is thought that Ganymede experienced heavy cratering at about the same time the Moon did (about 3.5 to 4 billion years ago). On Ganymede the darker areas of terrain tend to have heavy cratering whereas the lighter grooved areas have less cratering.

It is thought that Ganymede's icy crust is weaker than that found on the Moon or Mercury, leading to the craters having become more flattened over time.