Hogenboom
Other previous data which bear on the existence of high-pressure polymorphs of ammonia hydrates include the X-ray diffraction studies of Durham et al. (1993). In a study devoted primarily to ammonia–water ice rheology, those researchers discerned the existence of the familiar low-pressure polymorphs of ammonia mono- and dihydrate at pressures from 50 to 100 MPa, i.e., well below the subsolidus transition pressures we have found. (Polymorph A mineral that has several crystal forms; i.e. graphite is the amorphous form, while diamond is the crystal form, both being polymorphs of carbon.).
Our data confirm the result of Croft et al. (1988) that the NH3–H2O peritectic liquid has a density at low pressures (p0.946 g/cm3 at 0.1 MPa) that is less than the density of solid ammonia dihydrate I (p0.965 g/cm3) but greater than that of water ice I (0.917 g/cm3). 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. Not only is the presence of rock needed in the ice for ammonia to get extruded from the ice but the ammonia hydrate is more dense than water and sinks accumulating at the next base of hard ice/rock or rock layer.
These density relations extend to 160 MPa, above which the liquid is denser than ammonia dihydrate I up to p300 MPa, where a transition to ammonia dihydrate II occurs. A eutectic ammonia–water ocean is possible on icy satellites at pressures between 160 and 300 MPa.
Other previous data which bear on the existence of high-pressure polymorphs of ammonia hydrates include the X-ray diffraction studies of Durham et al. (1993). In a study devoted primarily to ammonia–water ice rheology, those researchers discerned the existence of the familiar low-pressure polymorphs of ammonia mono- and dihydrate at pressures from 50 to 100 MPa, i.e., well below the subsolidus transition pressures we have found. (Polymorph A mineral that has several crystal forms; i.e. graphite is the amorphous form, while diamond is the crystal form, both being polymorphs of carbon.).
Our data confirm the result of Croft et al. (1988) that the NH3–H2O peritectic liquid has a density at low pressures (p0.946 g/cm3 at 0.1 MPa) that is less than the density of solid ammonia dihydrate I (p0.965 g/cm3) but greater than that of water ice I (0.917 g/cm3). 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. Not only is the presence of rock needed in the ice for ammonia to get extruded from the ice but the ammonia hydrate is more dense than water and sinks accumulating at the next base of hard ice/rock or rock layer.
These density relations extend to 160 MPa, above which the liquid is denser than ammonia dihydrate I up to p300 MPa, where a transition to ammonia dihydrate II occurs. A eutectic ammonia–water ocean is possible on icy satellites at pressures between 160 and 300 MPa.
A eutectic is completely converted into a solution or melt upon an increase in temperature. Peritectic is the point of intersection between the temperature lines on a phase diagram at the onset of crystallization (solid). Eutectic is the point on a phase diagram where temperature converts the chemical to a liquid. peritectic vs eutectic is the temperature intersection between solid and liquid (crystalline and amorphous).
Water at 0° C can be both solid and liquid, both crystalline and amorphous, both peritectic and eutectic, at -1° C water is a solid, crystallized, peritectic, at +1° C water is a liquid, amorphous, eutectic, loosely speaking.
Among the most important unresolved problems in the geology of the icy moons is the origin of global extensional features on some but not all of these moons; these fractures indicate a net increase of surface area of several percent. We can now completely rule out earlier speculation solmagno 1985) that these extensional features could be caused by the melting and refreezing of NH3-rich liquids; it is now clear that the volume change is too small to account for the inferred expansion. Phase changes of H2O remain as expansion candidates but they raise other problems (Consolmagno 1985, Squyres and Croft 1986). Thus, this question remains unresolved. Another possible cause of global volume changes and tectonic stress raised by the new data is that of subsolidus phase transitions of ammonia hydrates.
The disappearance of the peritectic at 20 MPa is at a pressure reached inside all the principal icy satellites except Mimas, Enceladus, and Miranda (Kargel 1990); however, the high-pressure phases of the ammonia hydrates occur only above 300 MPa, i.e., pressures attained in the deep interiors of Ganymede, Callisto, Titan, Triton, and Pluto, but not in other icy moons (Kargel 1990). If Triton and Pluto have a dense rock/iron core, the icy mantle above morphs. It is likely that high-pressure ammonia hydrates served important roles in the evolution of Titan’s interior and atmosphere and possibly in the evolution of Ganymede and Callisto if they are ammonia-rich. Possible gravitational layering in both high-pressure water ice and ammonia hydrate phases should be considered in models of the geological evolution of large icy moons and in drawing structural interpretations from spacecraft-tracking gravity data (Schubert et al. 1994).
Water at 0° C can be both solid and liquid, both crystalline and amorphous, both peritectic and eutectic, at -1° C water is a solid, crystallized, peritectic, at +1° C water is a liquid, amorphous, eutectic, loosely speaking.
Among the most important unresolved problems in the geology of the icy moons is the origin of global extensional features on some but not all of these moons; these fractures indicate a net increase of surface area of several percent. We can now completely rule out earlier speculation solmagno 1985) that these extensional features could be caused by the melting and refreezing of NH3-rich liquids; it is now clear that the volume change is too small to account for the inferred expansion. Phase changes of H2O remain as expansion candidates but they raise other problems (Consolmagno 1985, Squyres and Croft 1986). Thus, this question remains unresolved. Another possible cause of global volume changes and tectonic stress raised by the new data is that of subsolidus phase transitions of ammonia hydrates.
The disappearance of the peritectic at 20 MPa is at a pressure reached inside all the principal icy satellites except Mimas, Enceladus, and Miranda (Kargel 1990); however, the high-pressure phases of the ammonia hydrates occur only above 300 MPa, i.e., pressures attained in the deep interiors of Ganymede, Callisto, Titan, Triton, and Pluto, but not in other icy moons (Kargel 1990). If Triton and Pluto have a dense rock/iron core, the icy mantle above morphs. It is likely that high-pressure ammonia hydrates served important roles in the evolution of Titan’s interior and atmosphere and possibly in the evolution of Ganymede and Callisto if they are ammonia-rich. Possible gravitational layering in both high-pressure water ice and ammonia hydrate phases should be considered in models of the geological evolution of large icy moons and in drawing structural interpretations from spacecraft-tracking gravity data (Schubert et al. 1994).
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SP is 3 km (1.86 miles) below surrounding terrain
1,300 x 900 km (808 x 560 miles) ellipse See a clear rim Do not see clear secondaries (perhaps erased by glaciers) No clear rings, but the mountains sort of line up where you expect rings Lack of rings/secondaries is reminiscent of Hellas, Mars There is a 1 km (0.6 miles) thick ejecta "collar" around SP! |
James Keane notes from Bill McKinnon lecture at Geological Society of America Sept 25th 2016
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This paper called "The Small Satellites of Pluto as Observed by New Horizons" explains how the poles of the small satellites are all nearly orthogonal (perpendicular) to the direction of Pluto and Charon's common rotational poles. In other words the small moons rotational axis are all nearly perpendicular to Pluto's axis. They roll around Pluto/Charon on their sides like Uranus does around the Sun.
| the_small_satellites_of_pluto_as_observed_by_new_horizons1604.05366.pdf |
Styx, Nix, Kerberos and Hydra (SNKH) are mostly orbiting on their side. Their pole alignments are 91°, 123°, 96° and 110° respectively. That means all of the small satellites are rotating backwards compared to Pluto and Charon which themselves are rotating backwards compared to the Sun. So the small satellites are rotating in a retrograde spin compared to Pluto/Charon but a prograde spin relative to the Sun.
There are several papers that suggest the small satellites are 4 billion years old and conclude they were formed in-situ (in their current orbital place) by accretion. These small moons supposedly accreted from the debris left over from the collision between Charon and Pluto.
If that were true why would all of them rotate the wrong direction?
Why would they be so bright?
Why would their spins be so erratic?
Ammonia hydrates were likely placed on the small satellites by Pluto 0.8 myr when conditions allowed the nitrogen at Sputnik Planitia to reach explosive triple point conditions. Sublimation pits on the surface of Sputnik Planitia are probably the nitrogen explosive bubble remnants and not sublimation pits at all. After all, why would nitrogen sublimate (evaporate) into the shape of cups. There is significant evidence that much of what has been called sublimation pits are actually sastrugi (wind blown snow) waves or ripple patterns.
There are several papers that suggest the small satellites are 4 billion years old and conclude they were formed in-situ (in their current orbital place) by accretion. These small moons supposedly accreted from the debris left over from the collision between Charon and Pluto.
If that were true why would all of them rotate the wrong direction?
Why would they be so bright?
Why would their spins be so erratic?
Ammonia hydrates were likely placed on the small satellites by Pluto 0.8 myr when conditions allowed the nitrogen at Sputnik Planitia to reach explosive triple point conditions. Sublimation pits on the surface of Sputnik Planitia are probably the nitrogen explosive bubble remnants and not sublimation pits at all. After all, why would nitrogen sublimate (evaporate) into the shape of cups. There is significant evidence that much of what has been called sublimation pits are actually sastrugi (wind blown snow) waves or ripple patterns.
Ammonia hydrates and crystalline ice were two items I thought I could use to potentially narrow down or identify the age of the event that created Charon's smooth southern hemisphere. Turns out neither is a reasonable age dating method for this event. Crystalline ice is found on other Kuiper Belts Objects (KBO) of similar size to Charon and the ammonia hydrates are spread across Charon's northern and southern surfaces but not around its trailing hemisphere. If the ammonia was predominately on the southern hemisphere it would suggest the event created the ammonia hydrates. If crystalline water ice were only on Charon it might also point to the event as a cause but neither is correct. Instead the leading hemisphere displaying ammonia indicates Charon's rotational orbit around Pluto is the key factor in the placement of the ammonia.
Zones - Rocky Planets, Main Asteroid Belt, Giant planets, Kuiper Belt Objects, Transneptunian Objects
Rocky Planets - temperature from Sun evaporates away volatiles
Main Belt - Frost line, Albedo shift
Giant planets - Centaurs, Trojans
Kuiper Belt - Cold Classical Red KBO, Neptune Perturbed (resonant) Multicolored Scattered Disk Objects, Plutinos
Transneptunian Objects,
Rocky Planets - temperature from Sun evaporates away volatiles
Main Belt - Frost line, Albedo shift
Giant planets - Centaurs, Trojans
Kuiper Belt - Cold Classical Red KBO, Neptune Perturbed (resonant) Multicolored Scattered Disk Objects, Plutinos
Transneptunian Objects,
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http://www.johnstonsarchive.net/astro/astalbedo.html
NASA's NeoWISE spacecraft has identified 29,375 solar system objects, including 788 near-Earth comets and asteroids. https://www.jpl.nasa.gov/news/news.php?release=2018-078
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https://www.nasa.gov/mission_pages/WISE/multimedia/neowise20130725i.html
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