Jupiter's inner four Galilean moons from nearest to furthest are Io, Europa, Ganymede and Callisto.
These four Galilean moons are so named because Galileo discovered them and witnessed them revolving around Jupiter demonstrating all objects do not revolve around the Earth. The Roman Catholic Church via the inquisition tortured and killed anyone that opposed their Earth centered view of the solar system. In 1543 Copernicus, to avoid torture wisely on his death bed, published his Sun centered model of our solar system. In 1610 the Roman Catholic church found Galileo guilty of heresy for sharing Copernicus' Sun centered view. The church, however, allowed Galileo the opportunity to recant his view and only imprisoned him for life. The density of a body gives a rough idea of how much of its compositional material is water, silicate rock or iron. Water's density is considered to be one gram per cubic centimeter, rock is about 3 g/cm3 while iron is 7.86. Earth's density is 5.514, the Moon is 3.346, Mars is 3.933, Tythes is 0.98. From this we can draw some basic conclusions. Saturn's moon Tythes is pretty much completely water ice with no rock or iron while Mars has more dense materials than our moon and likely has a small iron core relative to Earth. |
Io (eye-ohh)
Io is the closest Galilean moon to Jupiter and experiences the greatest degree of tidal flexing and resonance with Europa and Ganymede as it orbits near then far from Jupiter with pulsating resonances. Tidal flexing along with resonant interactions with Europa and Ganymede make Io the most volcanically active body in our solar system. |
Io was, in all probability, constructed of the same stuff as the other Galilean moons meaning it was once an ice ball like Europa, Ganymede and Callisto but all the ice and lighter materials have been evaporated away making Io the densest moon in the solar system at 3.528 g/cm3. This tidal flexing and resonant pulsing of Io is so strong it is even liquefying rock, turning it into magma. |
Europa
The 2nd closest Galilean moon to Jupiter is Europa and it has the smoothest surface in the solar system meaning its ice surface is renewed frequently and too thin to sustain mountains or significant uplift making its surface young. Cracks exist in its icy crust which spew out plumes of water meaning the hot core is heating the thin layered water ocean below. Europa has a density of 3.013 g/cm3) making it more rock than water ice hence there is a thin layer of water between the ice crust and hot silicate rock mantle. Most of Europa's water has been cooked away so it is small and primarily rock. |
Ganymede
Ganymede has enough tidal flex energy to liquefy the interior ices allowing for the development of a rocky core which is about the same size as Europa's with the primary difference being Ganymede hasn't lost such a large portion of it's water ice relative to the core. Lower flex (heat) energy means less of the water ice and volatiles have been burned or boiled off. This means Ganymede has a comparatively huge ocean relative to the rocky core. Because of this ratio disparity, the outer mantle remains intact sealing the interior away from space. |
Callisto
Callisto experiences the least amount of tidal flexing in the Jupiter system since it is farther out from Jupiter and is not sandwiched between other large resonant bodies. Callisto also doesn't show any signs of active land ice geology, Callisto is considered to be partially differentiation (partial rocky core). The mean temperature on Callisto is 134 Kelvin. Callisto is nearly the same size (about 99%) as Mercury but is only one third as dense at 1.834 (Mercury's density is 5.427) . Mercury is close to and heated by the Sun and is also in an elliptical orbit causing tidal flex these conditions on Mercury have done to it what an elliptical orbit and resonance around Jupiter has done to Io. |
There is very little energy from tidal flexing as Callisto is tidally locked to Jupiter (like Pluto is to Charon), consequently the "Rocky Core" or "Differentiated" Model begins to break down at this distance from Jupiter.
For full differentiation to take place at these temperatures some form of heat energy is required otherwise the rock stays suspended (at least partially) in the rock hard ice. |
The only moment of inertia value I found for Pluto was in this paper and is assumed to be 0.310. but this value changes depending on various assumptions contained within the paper. If the core is assumed to be a metal ball with a radius of 368 km, the moment of inertia changes to 0.290. This chart lists some calculated moment of inertia values for some planets and moons including Callisto. I was hoping the moment of inertia would help explain Pluto's mass distribution but what it seems to do is reflect assumptions we choose to feed into a formula. |
|
The moment of inertia controls the rate at which a planet spins and the location of the spin axis depend on the distribution of mass in each body... objects with more mass at the center have lower moments of inertia.
Objects with lower moments of inertia spin faster than objects with high moments of inertia. Pluto's moment of inertia is complicated because it's spin rotation is locked to Charon. They take 6.3875 days or 153.3 hours to rotate around their barycenter. In this video, objects with solid cores (low MOI) roll down the board faster than hollow cored tubes (high MOI). |
It would then appear, Pluto should have a higher moment of inertia than Earth (spin of 24 hrs) yet lower than the moon (spin of 29.5 days) placing it between 0.3307 and 0.3929. Mercury is supposed to have a 70% metal core with a 30% silicate rock mantle with a density of 5.427 g/cm3. |
Moving on to more easily understood and perhaps reliable factors of comparison.
Nitrogen on Pluto can flow (depending on pressure) at around 64 K while methane on Titan can flow at around 94 K and water needs to be around 273 K (mix in ammonia and water can be a syrupy liquid at temperatures as low as 173K). More specifically these compounds reach their triple point at particular temperatures combined with particular pressures. Nitrogen is the only material with observational evidence of being a fluid on Pluto and it requires far less energy than methane and water to flow or transition between a solid, gas and liquid state. |
I just read a paper called Internal structure of Pluto and Charon with an iron core in which an assumption about Pluto is made. The core of Pluto in this paper is assumed to be iron and at one point it was a ball of molten iron (shesh are you kidding me?). Shaking my head, I ask how do we get to a molten iron core at Pluto? Quote; But very early on Pluto was presumably hotter and the core molten. (assume it to be so and it is so. Voila molten metal.)
On page 56, I explain how, based on Robin Canup's collision model, Pluto and Charon had to be uniform not differentiated before collision or else the model couldn't work. Additionally they only survived a collision and remained as two separate bodies if they collided at slow speeds with a slight angle of impact keeping their temperatures primarily low enough to remain uniform. |
Comets & Asteroids
Comets are primarily ice with space dust locked in suspension.
Asteroids are comets with their volatile ices evaporated away that became space dirt balls which in turn transformed into rocks as they neared the Sun which in turn baked off the volatile ices leaving behind the harder material, |
Comet 67P
This is comet 67P Churyumov-Gerasimenko. The European Space Agency (ESA) sent a probe named Rosetta with a small lander on board called Philae to investigate 67P. This comet came from the Kuiper belt and is made of the same stuff as Pluto/Charon. Rosetta and Philae orbited and landed on 67P and collected some previously unknown information about comets.
Three of those discoveries at 67P stand out. Discovery 1. The water on 67P has 3 times the amount of deuterium as water on earth. This suggests water was not delivered to Earth by comets during the late heavy bombardment. |
Discovery 2. The dust on the surface of 67P is about 8 inches thick while the ice just below the surface is a mixture of ice and dust and is a very dense ice that is similar to rock.
This indicates a large amount of ice has sublimated out (evaporated) leaving the dust behind, 8 inches worth that's a lot of evaporated ice. This is the same ice water with embedded dust as on Pluto/Charon with the difference being a lack of heat to separate the dust out of the ice water. Eventually this dust will compress and pack itself into rock changing 67P into an asteroid if it doesn't first collide with something. |
Think of it like an Ostrich egg shell which is thick, rigid and protects the soft inner membrane from external compression forces.
An ostrich egg can withstand the weight of less than 120 kgs or 265 lbs. When impacts occur on Pluto's surface, the ice fractures settles then reforms, compressing tighter and tighter like a boa constrictor snake. |
Gas, Liquid, Solid
Elements that we view as gasses here on earth like nitrogen are actually solids on Pluto because of the 35° K cold temperature. On titan, 94° K, the gas we call methane exist as a liquid and a type of rain or snow, whereas, H2O is the rocky ground on both Titan and Pluto. Water on earth exist as a gas, liquid and solid depending on temperature.
Most elements will also go through these three phases depending on the temperature and pressure within which they exist. |
Mordor - One theory to rule them all
|
A Theory
|
This is my adjusted view based on all these observations,
A series of objects hurl through space and travel in clusters. They orbit around a central gravitational point just like Pluto and its moon's, This cluster of objects collided with Charon. Their sizes and shapes mostly matched the impacts on Charon's North pole as well as the moons Hydra, Nix, Kerberos and Styx. Previous impacts on Charon's Southwestern edge hit diagonally towards the Northeast cracking Charon along this diagonal line like an egg on a bowl. |