Download Figure 1 – [2] Callisto: The Secrets Within Amy Smith Physics 1040

Figure 1 – [2]
Callisto: The Secrets Within
Amy Smith
Physics 1040 Sec 11 T TR 10am
Solar System Paper
Our Solar System is home to over eight planets, moons or satellites, dwarf planets,
asteroids, comets, and meteors. With an age of approximately 4.6 billion years old, four terrestrial
planets (Mercury, Venus, Earth, and Mars), two gas giants (Jupiter, and Saturn), and two ice giants
(Uranus, and Neptune) [9]. NASA has a handful of spacecrafts and rovers completing missions
to retrieve information to help further educate scientists and all those interested in our Solar
System. There are at least 146 moons discovered by astronomers, with more to be confirmed [9].
The many objects that take residence in our Solar System, Callisto is among the few that I
personally found to be so unique and fascinating [9]. All of the objects in our Solar System are
similar in as many ways as they are different from one another; there are many characteristics of
Callisto that caught my attention out of all of the countless objects in our Solar System. The
appearance of Callisto, from its apparent magnitude, to its cratered surface have peaked my
fascination is this ancient moon in the Jovian System.
Callisto, known as Jupiter’s fourth satellite as part of the four moons discovered by Galileo
Galilei in the 17th century.
In the year 1610 Galileo made adjustments to his telescope which
allowed him to see celestial bodies more distinctly, revealing to him four satellites, or moons, that
orbited the planet Jupiter [1]. Originally named by their discoverer the four moons were known
as the Medicean planets after a very prominent and powerful family of that century, the Medici
family. Medicean moons I, II, III, and IV were identified as such until the mid-1800s where it was
a concern that to name satellites by numerical order of discovery would be cause confusion; the
names then were changed to IO, Europa, Ganymede, and Callisto [1]. Although the names of the
moons officially changed, they are accompanied by the original numerical name; the numerical
name began as a system created by Galileo to keep track of each celestial object discovered [5].
In regards to the original naming system as created by Galileo, the four Jovian satellites are as
numbered: Io as I, Europa II, Ganymede III, and Callisto as IV.
Callisto received the name from a character in a commonly known story in Greek
mythology. Callisto was the daughter of the King of Arcadia, Lycaon. As well as being the
daughter of King Lycaon, Callisto was also a hunting companion of the Goddess Artemis. As
required of all the hunting companions of Artemis, Callisto took a sacred vow of chastity. The
greedy and philandering God Zeus seduced the beautiful Callisto and as a result she was banished
by Artemis. In an effort to hide another of his affairs from his wife and Goddess Hera, Zeus
transformed the pregnant Callisto into a bear [3]. After Callisto gave birth to her son Arcas, Zeus
put them in the sky as the Giant Bear and Little Bear, more commonly referred to as Ursa Major
and Ursa Minor [3]. As Zeus is the “Greek equivalent of the Roman God Jupiter, [1]” it is not
hard to see the relation between the planet Jupiter and the name of the moon that is Callisto.
According to Kim Ann Zimmerman’s article featured on Space.com Callisto was, “thought
to be formed as a result from slow accretion from the disk of gas and dust that surrounded Jupiter
after its formation [3].” Callisto has the lowest density of the four Galilean moons and its thin
atmosphere is composed of many elements such as carbon dioxide [1 and 3]. With an average
temperature of around -218.47 degrees Fahrenheit the core is surrounded by an icy mantle; much
of the rocky material that makes up Callisto are “water-ice, magnesium and iron hydrated silicates,
sulfur dioxide, as well as other organic compounds[3].” In 1979 the Voyager 1 probe gave scientist
a first and closer look of Callisto’s surface which revealed an extensively cratered surface; the
craters on Callisto inform scientists that this moon is approximately 4 billion years old [4]. As
Callisto is the most cratered object in our Solar System, it is also the home of the oldest landscape
in our Solar System [1 and 3]. The craters on the surface of Callisto have remained unchanged
and with the absence of volcanoes and mountains on the surface, have led scientists to believe that
Callisto is no longer geologically active but a “dead moon” [1 and 3].
Figure 2 – [5]
Similar to the size of Mercury, Callisto is the second largest of the four Galilean moons
and is the third largest satellite in our Solar System [1 and 3]. Callisto has an orbital period around
Jupiter of 1,882,700km, making one day on Callisto equal to 16.69 days on Earth [1]. Callisto has
an equatorial circumference of 15,144.4km, with a mass of 1.0759 X 1023kg, and a surface area of
73,004,909.27km2. The surface gravity on Callisto is 1.236m/s2, making the escape velocity 5,460
mph [1].
Callisto is the outermost satellite of the four Jovian moons discovered by Galileo, and is
twice as bright as our Moon [1]. The four Galilean moons have apparent magnitudes ranging
from 4.6 to 5.6, and were the moons not so close to Jupiter it is believed they could be visible to
the naked eye. Even though the brightness of Jupiter takes away from the capability of the naked
eye to see the moons without visual aid, they can be seen with as little aid as low-powered
binoculars [5].
Galileo’s discovery of the “Medicean Planets” led to a completely new understanding of
our Solar System. Galileo not only proved that stars were not fixed celestial objects in the sky but
rather moving objects, but also unintentionally defeated the commonly accepted Ptolemaic world
system, which believed that Earth was the center of the Solar System and that all objects orbited
around the Earth, including the Sun [1 and 5]. With this break-through discovery and realization
Galileo accepted and proved the Copernicus theory and his heliocentric model of the Universe.
Copernicus wrote his essay “Commentariolus” that introduced the world to his idea of a
heliocentric universe model one hundred years previously to Galileo’s discovery [7]. Proving the
heliocentric model not only changed the world forever, but also proved the ethnocentrism and
resistance to change of the mass population.
Along with the change in the accepted model of the Universe, Callisto is also special in the
sense that it is believed to be a potential host or previous host to life. Although Europa is a more
probable life sustaining possibility than Callisto, the likely presence of an ocean still leaves it as a
possibility scientists will keep in mind and consideration until further information proves
otherwise [1, 3, and 5].
In 2009 NASA announced that there was a possible mission, the Europa Jupiter System
Mission, which would send two orbiters to complete extensive and detailed studies of the planet
Jupiter and its moons: IO, Europa, Ganymede, and Callisto [8]. The mission, if it precedes, would
launch in the year 2020, and the orbiters would reach the Jupiter system in the year 2026; the
orbiter spacecrafts would spend at least three years conducting detailed studies and tests to
complete their mission [8]. This mission would look at the specific qualities of each object that
have captivated observers, astronomers, and scientists alike. Ganymede which is the largest of the
four moons, would have its fascinating magnetic field studied. IO, as the most geologically active,
would be studied to better understand its cycles and processes. Europa would be searched and
analyzed for any possible life existence whether it be past, present, or future. As for Callisto, since
it is the oldest and most cratered, they would hope to gain from detailed studies any insights to the
formation of our Solar System.
As anyone can see Callisto is a fascinating celestial object that from its discovery has
continually shaped our conceptual world and left Earthly observers amazed by its marvel. As one
of the oldest and most cratered objects it contains many secrets and within them more extensive
meaning to its superficial beauty. To uncover Callisto’s hidden secrets and to further our education
of this moon would help our world to learn more about the formation of our Solar System. Gaining
more information on how our Solar System was formed would enlighten us on how our planet as
well as how ourselves as beings were formed.
Bibliography:
1. "Callisto: Overview." Solar System Exploration. N.p., n.d. Web. 18 Apr. 2014.
2. "Astronomy Picture of the Day." APOD: 2002 January 20. N.p., n.d. Web. 18 Apr. 2014.
3. "Callisto: Facts about Jupiter's Dead Moon." Space.com. N.p., n.d. Web. 18 Apr. 2014.
4. BBC News. BBC, n.d. Web. 20 Apr. 2014.
5. "Galilean Moons." Wikipedia. Wikimedia Foundation, 16 Apr. 2014. Web. 17 Apr. 2014.
6. "Callisto." Callisto. N.p., n.d. Web. 20 Apr. 2014.
7. Rabin, Sheila. "Nicolaus Copernicus." Stanford University. Stanford University, 30 Nov. 2004.
Web. 17 Apr. 2014.
8. Dunbar, Brian. "NASA and ESA Prioritize Outer Planet Missions." NASA. NASA, 18 Feb.
2009. Web. 20 Apr. 2014.
9. "Our Solar System: Overview." Solar System Exploration. N.p., n.d. Web. 19 Apr. 2014.