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Ganymede, Among Jupiter’s Moons.
Katrina Scanlan
Salt Lake Community College
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Abstract
Ganymede, the largest moon in our solar system and is the 27th named moons of Jupiter. Even
though Ganymede is determined to be a moon because it orbits Jupiter, but if Ganymede were to
orbit the sun instead then it could be easily mistaken for a planet instead of a moon because of its
massive size. Ganymede is as big as Mars and could cover both Mercury and Pluto in size
(Ganymede, 2013). Although the size and the geological activities that occurs on Ganymede is
very fascinating the mythological story that gave Ganymede its name sounds interesting as well,
so there will be both the science and the non-science parts involved with the telling of
Ganymede, Among Jupiter’s Moons.
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Ganymede, Among Jupiter’s Moons.
Galileo Galilei discovered Ganymede on the 7th of January 1610 and along with that
Galileo also discovered three other Jovian moons and this was the first time Galileo saw other
moons that were orbiting other planets as well and not just earth itself. Jupiter’s moons were
originally called the Medicean planets and were each numbered off and it wasn’t until the mid1800’s that the names Ganymede, Io, Europa and Callisto were adopted by Jupiter’s moons
because the numbering system was getting too hard to keep track of (LaLeutwyler, 2003)(Lang,
2003).
A Mythological Perspective
The mythological story that is attached to Jupiter’s moon Ganymede is very interesting
and it all begins with a young and beautiful boy named Ganymede. This young boy became one
of Zeus’s lovers as legend has it. Ganymede was herding his flock on Mount Ida when Zeus fell
in love with him. Zeus disguised himself as an eagle or he sent an eagle to snatch Ganymede and
take him to Mount Olympus were he then became a cupbearer to the gods. Hera, the wife of
Zeus, was so outraged and jealous of the love that Zeus had for Ganymede, who was just the
cupbearer, that Zeus put Ganymede in the stars as the constellation Aquarius, the water carrier
(Gibson, 2004).
Some say that the story of Zeus and Ganymede reflected what Greek life was at that time
and how males didn’t need the existence of women, that’s why males were mainly dominant at
the time. Although now we do have a different perspective on how things were viewed at that
time and we no longer follow that way, we now take things into a science perspective on how we
determine the things that happens in our solar system.
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The Facts about Ganymede in our Solar System
Orbit Circumference
Average Orbit Velocity
Orbit Eccentricity
Orbit Inclination
Mean Radius
Equatorial Circumference
Volume
Mass
Density
Surface Area
Surface Gravity
Escape Velocity
Sidereal Rotation Period (Length of Day)
Atmospheric Constituents
(Ganymede, 2013).
Metric: 6,725,518.71 km
Metric: 39,165.6 km/h
0.0013
0.177 degree
Metric: 2,631.2 km
Metric: 16,532.3 km
Metric: 76,304,506,998 km3
Metric: 148,185,846,875,052,000,000,000 kg
Scientific Notation: 1.4819 x 1023 kg
Metric: 1.942 g/cm3
Metric: 86,999,665.93 km2
Metric: 1.428 m/s2
Metric: 9,869 km/h
English: 6,133 mph
Scientific Notation: 2742 m/s
7.155 Earth days
By Comparison: Synchronous with orbital period
Oxygen
Ganymede can be viewed with the naked eye because it was discovered in the early
Chinese astronomical records and although Ganymede is much larger than Mercury in size but it
is low in density. The temperature can vary as well, during the daytime the surfaces average
temperature can go from -171F to -297F and during the night the temperature drops to -193C
which is why there likely will not be any living inhabitants on Ganymede. Ganymede has a
metallic iron core which are then layered on by rocks and then crusted off with mostly thick ice.
Ganymede’s surface is made up of two types of terrain, 40percent dark with craters and
60 percent light with color and patterns which gives Ganymede its appearance. The light is
formed from the result of tectonic activities and/or the water that is released from beneath the
surface which can stretch for thousands of miles. Ganymede is believed to have salt water oceans
below the surface. The atmosphere on Ganymede is a thin layer of oxygen, but still too thin to
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ever support life, and the only moon in the solar system to have a magnetosphere, which are
mainly found in planets including Earth and Jupiter itself (Zimmerman, 2014).
The Activities that Occur on Ganymede
Many scientists assumed that volcanic activity were in the ice instead of rock and not
that much tectonic activities were responsible for creating Ganymede’s newer surfaces. The
largest are on Ganymede is called Galileo Regio. The large craters on Ganymede almost has no
vertical relief and they are quite flat. These craters lack central depressions that are common on
craters found on the surface of the moon (Ganymede, 2013). Meteor or comets that crashes into
Ganymede splatters ejecta, wet like egg, across the face of the moon and scientists have named
more than one hundred of these craters on Ganymede, many of the very ancient ones ranging in
size from tens to hundreds of kilometer in diameter. The pit that is seen on the face of Ganymede
measures about 150 kilometer wide and is named Osiris, the ruler of the underworld.
The craters can also give off clues as to Ganymede’s composition. There are some signs
that also show that Ganymede does not only have an appearance of a planet but it also sounds
line one too. “Ganymede’s song”, a space craft reached the edge of Ganymede’s magnetic field
and there was a loud burst of noise. There was one irregular tone in particular, that associated
with the density of charged particles, rised to a peak and then it drops off and after that another
loud burst signaled a sign of “Ganymede’s song” coming to an end and the spacecraft left
Ganymede’s magnetosphere (LaLeutwyler, 2003).
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The Probes that have landed on Ganymede
Some of the probes that have landed on Ganymede were: Voyager 1 in 1979, Voyager 2
presumably in 1979 as well, and the Galileo’s Solid State Imaging (SSI) in 1997 (Galileo
Orbiter) (Ganymede, 2013). Even though
there are not that many space probes that
are sent out to Ganymede it can still be
seen with a Telescope and as mentioned
earlier, with the naked eye as well
because of how huge Ganymede is in size
(LaLeutwyler, 2003).
The Space Dust on Ganymede
Collisions like Osiris can cause considerable amounts of debris to occur on Ganymede.
Some of the impacts caused by the collisions are so forceful that they hurtle icy material from the
crust that can stretch out for hundreds of kilometers, which also creates bright networks of rays.
When these icy materials are forced out of the crust they can also vaporized meteoroids as they
strike. Space rocks can vanish instantaneously into puffs of dust and these explosions can also
propel individual dust grains at great speeds that most of them can escape the gravitational field.
Some of the other Jovian planes can collect dust and form rings around these giant planet, but a
few grain remains trapped which forms a dusty cloud around Ganymede. Not only does
Ganymede have these dusty halos but so does Callisto and Europa as well (LaLeutwyler, 2003).
Comet Crashes that Occurs on Ganymede
There are some photos of a comet frozen upon Ganymede’s surface that would have
revealed strings of rocks attached to it. Thirteen comet fragments rained down upon Ganymede’s
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surface in rapid succession, forming a catena (a chain of craters) about 120 kilometers in length.
Even though it appears as though the ejecta covered only the light terrain, scientists suggested
that the crashed has probably stirred up both the light and the dark material that soon later
blended into the dark ground. Ganymede is not the only one that this chain has occurred to as
well, later some were found on Callisto, Luna, Earth, and other moons and planets (LaLeutwyler,
2003).
Conclusion.
Even though Ganymede is as big as it is and is called a moon instead of a planet it is still
the largest moon out there in solar system. Ganymede was discovered by Galileo and was then
given a number. Not long after Ganymede adopted its name from a mythological story. The
mythological story was very interesting on how it started out with Ganymede being a beautiful
young male and how Zeus fell in love with him that it cause Hera to become jealous, forcing
Zeus to get rid of Ganymede. Although instead of doing that Ganymede was placed into the stars
as Aquarius. It may have seemed that Ganymede was geologically active a long time ago we still
see a bit activity still happen on Ganymede today and though many probes hasn’t visited
Ganymede that often it still shows to be a very unique moon in our solar system.
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References
Ganymede: Overview. (2013). Retrieved October 13, 2014, from
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Ganymede
Gibson, M. (2004, January 1). Ganymede. Retrieved October 13, 2014, from
http://www.pantheon.org/articles/g/ganymede.html
Jupiter: Overview. (2013). Retrieved October 13, 2014, from
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Sats
LaLeutwyler, K. (2003). Ganymede. In The moons of Jupiter (pp. 146-187). New York: W.W.
Norton.st Name, F. M. (Year). Article Title. Journal Title, Pages From - To.
Lang, K. (2003). The Cambridge guide to the solar system. Cambridge, U.K.: Cambridge
University Press.
Zimmerman, K. (2014, January 1). Ganymede: Facts About Jupiter's Largest Moon. Retrieved
October 13, 2014, from http://www.space.com/16440-ganymede-facts-about-jupiterslargest-moon.html