Report on the Jupiter Moon Callisto

It should be common knowledge that Earth has one moon, and other planets have more or less. For example, Mercury and Venus have zero moons, and Jupiter, on the other hand, has many moons, 95 to be exact. One of Jupiter’s moons is Callisto. Callisto is the second largest of Jupiter’s moons and the third largest moon in the solar system.
Jupiter’s moons fall under three categories: the Inner Moons, Outer Moons, and Galilean Moons. All of the moons however fall under a blanket term of the Jovian System. The Inner Moons are the moons closest to Jupiter and almost all of them are small, the Outer Moons are irregularly shaped and more distant from Jupiter, and the Galilean Moons are the largest and most studied moons. There are four Galilean Moons, Io, Europa, Ganymede, and Callisto which is the moon I will be focusing on today. Callisto was first discovered by Galileo in 1610 and was observed independently by Simon Marius.
Callisto is one of the well-known moons of Jupiter and it is known that the moon is quite large. Well, to be exact Callisto is around the same size as the planet Mercury, to be exact Callisto is 4,800 kilometers or 3,000 miles in diameter. The question may be then, “Why is Callisto not a planet?” The answer to this question is simple, Callisto is not considered a planet because it is not in direct orbit around the sun. If Callisto was in direct orbit of the sun then the moon would be considered a major planet. The moon is over a million miles from Jupiter so the orbital distance between the moon and the planet is quite large, this means that it takes just about 17 days for Callisto to make one revolution around Jupiter.
Callisto has been nicknamed a ‘dead planet’ for many years, this is because the moon has evidence of erosion and ice along with many other things. The moon has an icy surface that is covered with craters. These craters vary in size and shape, with some having multiple rings around the crater and bowl-shaped craters. Callisto is made up of Iron and Magnesium silicates, along with sulfur dioxide and carbon dioxide. On November 4th, 1996, the Galileo spacecraft gathered data that showed that Callisto may have a subsurface ocean, although studies done more recently show that the ocean may not exist or it is far deeper than was originally thought. If there is an ocean scientists believe that Callisto may be able capable of supporting life. If there is an ocean, the ocean would be salty and interact with layers of rock, which would be the key conditions for creating life. Inside Callisto is made up of multiple layers of rock and metal, with multiple layers of ice. In 1999 scientists at NASA detected through the Galileo spacecraft that Callisto had a thin exosphere or atmosphere made up of carbon dioxide. In more recent years researchers have discovered that oxygen and hydrogen may also be in its exosphere. The moon is currently on a list of places where life can exist beyond Earth.
The thing that makes Callisto so interesting is the fact that the moon may be able to support life. Currently, for scientists exploring space, this is important because they are trying to find planets and moons for humans to possibly live on. There have been many space missions to Callisto including the Galileo spacecraft which has already been mentioned, along with Cassini spacecraft and New Horizons. Spacecraft that have explored Callisto or Jupiter are the Juno spacecraft, Hubble Space Telescope, Voyager 1, Voyager 2, Ulysses, Galileo Jupiter Atmospheric Probe, and Pioneer 10. In 2030 The Europa Clipper which was launched on October 14, 2024, will start conducting flybys of Callisto. This spacecraft may also land on Callisto which would be the first time a spacecraft has landed on Callisto. NASA did a study in 2003 called Human Outer Planets Exploration or HOPE. This study thought about a future in human exploration of the outer solar system. The target of this study was Callisto. In the study, scientists proposed that there could be a surface base on Callisto that could produce rocket propellant for even more exploration of the solar system. The advantage of having a base on Callisto is that there would be less radiation due to the moon’s distance from Jupiter and the geological stability that Callisto has. NASA has stated that in the 2040s a crewed mission to Callisto may be a possibility.
There have been many proposals to send more spacecraft out to Callisto and Jupiter. Some of these proposals include the Europa Jupiter System Mission or EJSM which was proposed to launch in 2020. In February of 2009 the European Space Agency and NASA proposed the Titan Saturn System Mission, other missions also include the Jupiter Europa Orbiter, the Jupiter Ganymede Orbiter, and the Jupiter Magnetospheric Orbiter. On April 14, 2023, the ESA’s Jupiter Icy Moons Explorer, or JUICE for short is estimated to do 21 close-up flybys of Callisto within the years of 2031 and 2034.
Callisto stands out as one of the most fascinating celestial bodies in our solar system due to its size, unique geological features, and the potential for supporting life. As the second largest of Jupiter's moons, it captivates scientists not only because of its icy surface and extensive cratering but also due to the intriguing possibility of a subsurface ocean. The ongoing exploration of Callisto, fueled by missions like the upcoming Europa Clipper, underscores humanity's quest to understand better our cosmic neighbors and identify environments where life might exist beyond Earth. As we continue to study this captivating moon, we inch closer to unlocking the mysteries of our universe and the possibility of finding life beyond our home planet.