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thermal_evolution_of_pluto_and_implications_for_surface_tectonics_and_a_sub-surface_ocean_guillaume_pluto.pdf | |
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reorientation_of_sputnik_planitia_implies_a_subsurface_ocean_on_pluto_nimmo_hamilton_mckinnon | |
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Croft et al., produced this phase diagram of ammonia di and mono hydrates as well as pure ammonia.
The dashed line represents the density of water ice 1h but appears to be off slightly as it reflects an H2O ice density of 0.93 not 0.917 g/cm^3 (or more likely there's something I don't understand about it). The important thing to glean from this is what Hogenboom says about it. Liquid NH3-2H2O is less dense than solid NH3-2H2O and both liquid and solid NH3-2H2O are more dense than frozen 1h water ice. Hogenboom Our data confirm the result of Croft et al. (1988) that the NH3–H2O peritectic liquid has a density at low pressures (0.946 g cm^3 at 0.1 MPa) that is less than the density of solid ammonia dihydrate I (0.965 g cm^3) but greater than that of water ice I (0.917 g cm^3). Hence, NH3–H2O liquid can be extruded from a rock-rich icy mantle and through a thick ammonia hydrate crust, but it cannot be extruded readily through a thick mantle or crust of water ice I. These density relations extend to 160 MPa, above which the liquid is denser than ammonia dihydrate I up to >300 MPa, |
In a nutshell Hogenboom is saying this;
The rocky core is more dense than the solid ice ammonia hydrates so the solid NH3-H2O is extruded (squeezed) from the rock core. Solid frozen ammonia hydrates are more dense than its liquid counterpart so liquid NH3-H2O is extruded from the solid hydrate. Water ice 1h is less dense than the liquid hydrates so it is extruded or floats on top of all these denser materials. Its like a layered cake of rock, solid NH3, liquid NH3 then H2O ice 1h. Less dense stuff layers or stratifies on top of denser stuff. |
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Look at the size of the "Theoretical Rocky Core" (gray) in the above drawing. It extends outward to 850 km. The pressure that pure ice (density of 0.917 g/cm^3) would place on this rocky core is slightly less than 200 MPa (base of the pink band).
High pressure polymorphs develop at pressures above 300 MPa. Low pressure polymorphs exist between 50 and 100 MPa. Basically there are high and low pressure ammonia hydrates just as there are low and high pressure water ices (Ice I & Ice II). Low pressure ice is crystalline with a strong lattice similar to a rigid scaffold whereas high pressure ice is amorphous (the lattice structure collapses into a disorganized form). ![]()
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They present the below graph (Fig 3) to support the idea that an ice shell on Pluto could survive for 4 byr.
I placed red vertical lines at 62.5 (their thin ice shell size) and 150 km (their thick ice shell size) which correspond to temperatures of 201 K and 184 K respectively.
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The above Nimmo et al., chart indicates that to maintain a thin shell of 62.5 km for 4 byr the temperature would need to be 201 degrees Kelvin. The thin shell directly below Sputnik Planitia (SP) must have a temperature of 201 K.
On the other hand, to maintain a thick shell of 150 km for 4 byr, the temperature of the ammonia infused ocean water would need to be 184 K. The warmer the temperature the thinner the ice shell. Do you see the problem? The temperature must rise (get hotter) as the ocean gets farther from its heat source in order to maintain a thinner shell. |
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The temperature is rising the further we migrate away from the heat source??????????? Here again is an example of a model that focuses on one thing (the effect of temperature on shell thinning to prove a 4 byr old ocean forming processes is viable) while completely ignoring its logical impossible conclusion. Dooohhhh!!!! |
This is a James Keane drawing of a lecture by Mathew Walker about Jupiter's moon Europa.
This is a logical and reasonable explanation of how convective and conductive processes take place. There is consistency in the sequence of events unlike the logic applied by Nimmo's inverted heating scenario above. In this scenario convective processes exist below conductive processes which makes sense. On Pluto opposite logic is postulated which makes no sense. |
According to Hogenboom's experiments, a 5% (red lines) concentration of NH3 dissolved into water at 100 MPa of pressure (175 km deep) needs a temperature greater than 259 K for the solution to be liquid.
At 200 MPa (352 km deep) this 5% concentration of NH3 must be warmer than 246 K to remain a liquid but that's a mute point as we bounce into a theoretically radioactive hot rocky core at 338 km. With a higher concentration of 10% ammonia (blue lines) and at a depth of 175 km (100 MPa) the temperature must be greater than 250 K to keep the solution liquid. At this 250 K temperature Pluto's ice shell according to Nimmo's graph, cannot last 4 byr. |
At a depth of 352 km (200 MPa) a 10% ammonia rich solution needs to be warmer than 238 K to remain a liquid, this would make Pluto's outer ice shell about 10 km thick after 4 byr according to Nimmo's chart but this thin outer shell would not support the 2.5 mile high mountains at Norgay Montes.
As the pressure decreases the temperature must increase in order to keep the solution in a liquid state. To keep the top of Nimmo's ocean dome liquid with a concentration of 10% ammonia, the temperature at the dome roof would need to be around 260 K (green line in above ammonia water chart). At this temperature there would be no dome or crustal shell according to Nimmo's graph. |