Enceladus Case

Enceladus Report

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Enceladus is one of Saturn's few geologically active moons and is one of the iciest bodies in our solar system. First discovered on August 28th, 1789 by Sir William Herschel, Enceladus was the sixth moon of Saturn to be found. Enceladus was nameless for years until Herschel's son published a work in 1847 suggesting that the satellites be named after the Titans. Before his publication, Enceladus was simply known as Saturn II. Enceladus' name comes from a child of Gaia, also known as a Titan, which had snake-like limbs and was killed by the goddess Athena. Saturn is named after the Greek god Cronus, the leader of the Titans, therefore it only fits that Enceladus is named after one of them (Redd).

Synchronous with Saturn, the rotation period of Enceladus is about 10 hours and 34 minutes. The radius measures 252.1 km, and is about as wide as Arizona. The mass is 107,944,591,230,692,000,000 kg or 1.0794 x 1020 kg, which is only a fraction of Earth's mass. The density measures 1.608 g/cm3 ("Facts & Figures"). Enceladus reflects almost 100% of light and has the highest albedo (>0.9) of any body in the solar system due to the high amount of ice located on the moon (Arnett). Enceladus' composition consists of 91% Water vapor, 4% Nitrogen, 3.2% Carbon dioxide, and 1.7% Methane ("Enceladus (moon)"). At its closest, Enceladus is 236,918 km away from Saturn and 239,156 km at it's closest. The escape velocity measures 861 kilometers per hour. The orbit eccentricity is .0047, therefore the orbit is fairly circular. The orbit circumference measures 1,495,622.32 km and the orbital period is 33 hours. The orbit inclination is very small, measuring only .009 degrees ("Facts & Figures").

Enceladus' surface is a very interesting place. Enceladus has five surface features, including plains, craters, grooves, trenches and ridges. Each of these features on the surface are named for characters and places from the collection of West and South Asian stories known as One Thousand and One Arabian Nights. The craters stretch no longer than 35 km across while some regions are smooth and free from any sign of impact, which implies there was resurfacing of the planet (Redd). This resurfacing can be attributed to water volcanism. The surface of Enceladus has undergone much deformation and fracturing due to the icy surface. The temperature of the ice affects how easy Enceladus can change; warmer ice is easier to deform over more cold, stiff ice. Grooves, ridges, rifts, and troughs along Enceladus' surface are attributed to tectonics. The canyons can be up to 200 km long and many of them cut across other surface features such as craters, which prove that they are relatively young features. The impact cratering along the surface allows scientists to date the moon to either 170 million years old or 3.7 billion years old, depending on the "assumed impactor population" ("Enceladus (moon)").

It is believed there may be a subsurface ocean residing underneath the ice along Enceladus' surface. Proof of this can be viewed at Enceladus' South Pole where over 70 geysers vent icy material into space. Around this area, there are blue-greenish ridges labeled as ‘tiger stripes.' These stripes appear to be quite young, dating less than 1000 years old. The subsurface ocean makes life on Enceladus a very real possibility. Especially since simple organic compounds have been discovered lurking within the tiger stripes of the moon. ("Enceladus (moon)"). Matt Hedman, a Cassini team scientist, said "The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away. We think this has to do with how Saturn squeezes and releases the moon with its gravity." To which Christophe Sotin quoted, "The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water" ("Saturn's Enceladus").

Because Enceladus undergoes tidal heating through an orbital resonance, it is possible for it to be geologically active. Geologic activity has caused resurfacing in many areas and has also caused many of the surface features located on Enceladus. The grooves around the South Pole appear to be warmer than other areas and the geysers that vent giant clouds of icy crystals and water vapor prove geologic activity (Bennett, 338). These geysers must come from a subsurface source, hence the idea of a subsurface ocean. The cryovolcanoes along the surface are also currently active, which makes Enceladus one of four bodies in our Solar System to still be geologically active. During a Cassini mission, a bending of the magnetic field of Saturn was viewed, with the magnetospheric plasma being slowed and deflected by Enceladus. The deflection is believed to be caused by ionized water vapor ("Cassini").

The Cassini-Huygens mission to Saturn was reveal that Enceladus has a significant atmosphere. It is believed by astronomers that Enceladus' atmosphere was possibly created by volcanism, geysers or some other means of gasses escaping from the surface or interior of the moon. Cassini flew through a gas cloud created by a cryovolcano (water and other volatiles erupted instead of the usual silicate rock) and was able to analyze the composition of the cloud ("Cassini"). Before the Cassini mission, there was little known about Enceladus' interior, but now we have a better clue as to how the interior actually is. Enceladus' inner core is believed to be silicate. Its outer core is thought to be a mixture of water and ice. After the Cassini mission