September 7th, 2017
This page is only speculative and likely has some basic flaws but I'm pretty sure the overall concept is correct, that being there is an oscillating tidal bulge at Pluto's minimum principle axis of inertia.
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Earth's axis is tilted 24 degrees and precesses 360 degrees drawing a circle in the heavens every 26,000 years.
This overhead circle is known as the precession of the equinox. There is a point where the Earth's polar axis, the orbital plane and the equatorial plane intersect. This animation makes it easy to understand. The precession of the north pole in this animation is backwards. The white line in the video represents Earth's polar alignment as it rotates over 26,000 years but pay attention to the red line as it cuts a clean horizontal path through the constellations. |
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As long as the pole alignment is steady the equatorial plane will cut a clean horizontal line but if the polar alignment wobbles then the horizontal line will oscillate.
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Earth's poles not only precess but they also wobble or oscillate up and down as they precess so the horizontal circle drawn is not a clean circle but more of an oscillating wavy circle.
The relatively tiny wobbles are called nutations the longest of which takes 18.6 years Nutations are very short term wobbles. Nutation have periods from as much as 18.6 years down to 5.5 days. Milankovitch cycles are 41,000 year cyclical changes in weather patterns based on Earth's movement through space. |
Three factors that influence Milankovitch weather (temperature) cycles
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Axial Tilt (Obliquity)
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Axial Spin (Precession)
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Oval Orbit (Eccentricity)
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On Earth, Milankovitch weather cycles occur over long time scales of 41,000 years. This cycle has been used to explain the occurrence of ice ages as they match the 41,000 year pattern.
Nutations are short term oscillation in the precession cycle. (a more detailed video). Nutations on Earth are created by the gravitational influence of the Sun and Moon but also by shifting ocean tides which are also influenced by winds. That's right wind can cause the Earth's axis to wobble slightly. Nutations take place in as short a time scale as 14 months.
Cycles, Oscillations, Wobbles, Precession, nutation, Milankovitch
Extract from the abstract of this paper
Precession Relaxation of Viscoelastic Oblate Rotators
Perturbations of all sorts destabilise the rotation of a small body and leave it in a non-principal spin state. In such a state, the body experiences alternating stresses generated by the inertial forces.
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Wiki Quote on Milankovitch cycles
The angle of the Earth's axial tilt with respect to the orbital plane (the obliquity of the ecliptic) varies between 22.1° and 24.5°, over a cycle of about 41,000 years. (A two degree axial oscillation matching the frequency of Milankovitch weather cycle) The current tilt is 23.44°, roughly halfway between its extreme values. The tilt last reached its maximum in 8,700 BCE. It is now in the decreasing phase of its cycle, and will reach its minimum around the year 11,800 CE. Bear with me, I'm getting to the point. |
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When Earth's poles precess over 26,000 years, the horizontal line at the cross section of the orbital and equatorial plane remains steady and draws a clean horizontal path through the constellations but that's not really how things work. Oscillations occur (both short term nutation and long term Milankovitch cycles ) which then make the horizontal path oscillate up and down. On Earth, Milankovitch cycles of only 2 degrees cause the central horizontal line to trace small oscillations at the intersection point on Earth's orbital and equatorial plane.
Obliquity (axial tilt), eccentricity (orbital elongation), precession (wobble) and nutations (wiggle) cause Earth's climate swings into and out of ice ages. Earths eccentricity is only 0.0167 nearly circular while Pluto's orbital eccentricity is 0.2488 (very high). When Pluto was a planet it's orbit was the most eccentric but now that its just another Transneptunian Object. Pluto's eccentricity is not that extreme compared to objects like Eris and Sedna with eccentricities of 0.44 and 0.855 respectively but it is extreme compared to Earth.
Pluto and Charon rotate around their barycentric point in 6.4 days. Since Pluto and Charon are tidally locked they appear stationary relative to each other but their poles twist and torque by 24 degrees on long time scales of 1.4 Myr and when one twists it induces a gravitational torque (stress) on the other. This 24 degree swing creates alternating long term different weather conditions from extreme to moderate. Pluto takes 248 years to orbit the Sun so every 11,290 orbits (Pluto years) equals one Milankovitch cycle.
Obliquity (axial tilt), eccentricity (orbital elongation), precession (wobble) and nutations (wiggle) cause Earth's climate swings into and out of ice ages. Earths eccentricity is only 0.0167 nearly circular while Pluto's orbital eccentricity is 0.2488 (very high). When Pluto was a planet it's orbit was the most eccentric but now that its just another Transneptunian Object. Pluto's eccentricity is not that extreme compared to objects like Eris and Sedna with eccentricities of 0.44 and 0.855 respectively but it is extreme compared to Earth.
Pluto and Charon rotate around their barycentric point in 6.4 days. Since Pluto and Charon are tidally locked they appear stationary relative to each other but their poles twist and torque by 24 degrees on long time scales of 1.4 Myr and when one twists it induces a gravitational torque (stress) on the other. This 24 degree swing creates alternating long term different weather conditions from extreme to moderate. Pluto takes 248 years to orbit the Sun so every 11,290 orbits (Pluto years) equals one Milankovitch cycle.
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On Pluto the polar axis is tilted 120 degrees, Earth's axial tilt is 23.5 degrees.
Pluto's Milankovitch cycles oscillate up and down 24 degrees, Earth's is 2 degrees. Pluto's eccentricity is 0.2488 while Earth's is a mere 0.0167. The conditions on Pluto that set up Milankovitch cycles are extremely extreme compared to Earth. The small changes in Earth's orbit, tilt and preccesion are enough to turn Earth into an ice ball or blazing hot wasteland. Consider how much more extreme the climatic changes would be on Pluto. As Pluto's pole oscillates or wobbles 24 degrees, it torques on Charon and the equatorially aligned smaller satellites and a circular stress in the form of a rotating tidal bulge is felt encompassing Sputnik Planitia at zero degrees latitude and 180 longitude. |
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I'm not aware of any data that suggests Pluto and Charon experience short term nutation wiggles but based on the fact that Pluto experiences extreme Milankovitch conditions and there are four small satellites in bizarre spins with polar misalignment to Pluto/Charon, its probable there is some short term nutation wiggle taking place during the 1.4 myr Pluto precession wobble.
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As Pluto's north pole experiences its 24 degree Milankovitch cycle it also has to turn Charon's poles such that the two maintain their polar alignment.
This torquing twisting effect will generate heat energy at the central point between the two planets. Since they are tidally locked and their poles wobble 24 degrees a circle of tidal flex energy (wandering bulge) would occur focused directly at the Charon and anti Charon point. Since these two planets are so close to each other in size and distance the torque stress forces are relatively extreme. 
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Credit James Keane
<<<<<<<< I took this topographical map by F. Nimmo which has a small black X indicating the center of Sputnik Planitia at 18 degrees north, 175 east. I added a large red X at the center point between Pluto and Charon's Minimum Principle Axis of Inertia and drew a rough blue circle with a diameter of 24 degrees. This is the primary point of stress or tidal flex energy (bulge migration zone) induced onto Pluto by Charon and vice versa as they wobble through their long term Milankovitch cycles and short term nutations. |
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Pluto is getting some official names for some of its land features. That which was once Norgay Montes is now officially Tenzing Montes. I'm glad they haven't named the old Wright Mons as it does not deserve to be recognized as a distinct feature like a cryovolcano.
As Pluto/Charon revolve through their 24 degree cycle a circular energy tidal flex footprint (bulge) is felt directly around the blue circle I've drawn on Pluto. Pluto's gravity would then collapse the stressed water ice crust at this location grinding and inducing some heat energy warming any subsurface N2. |
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While we can't see whats below 30 degrees south, we can see that much of this Tenzing area (old Wright Mons) doesn't show any signs of impacts.
The material in this area is rough with 2 mile high land mass elevations but it is able to absorb impacts then back fill on short time scales (moderate heat energy). The surface of SP is obviously comparatively soft as it is primarily smooth and has zero impacts (high heat energy). To the east of SP, contained within the uplands, lakes of fluids are mingled with sharp long angular penitentes yet no impacts (moderate heat energy). |
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The entire area where there's a lack of impact craters (outlined in white) is called Tombaugh Regio and looks like the outline of the Walt Disney dog character named Pluto. Seems the universe has a sense of humor. The 2.5 mile high water ice mountain peaks at Tenzing Montes sitting in a land area where there are no impact craters indicates one of two scenarios. The high mountains are either floating in a really deep buoyant pit of nitrogen ice (water ice floats in N2 ice) or they are partially floating while resting on deep bedrock ice surrounded by softer N2 material.
In 2010 a Chilean earthquake shifted the Earth's axis of rotation by 2.7 milliarcseconds (about 8 centimeters, or 3 inches) and caused the Earth's rotation speed to increase slightly. In 2004 the Sumatran earthquake shifted the Earth's axis of rotation by 2.32 milliarcseconds (about 7 centimeters, or 2.76 inches) it also caused the Earth's speed to increase. While these are not large changes in speed or axial shift they do demonstrate how collapsing land (via subduction) redistributes the mass of the Earth, changing the rotation speed, the axial tilt, its nutation (wiggle) and its precession (wobble).
SP is a 2 mile deep sunken basin. As SP collapses under gravitational torque stresses and the wandering tidal bulge, Pluto's mass distribution changes in turn inducing shifts in rotation speed around its barycenteric point which would need to be counter balanced by Charon's gravitational breaking force. The axis would also shift causing a twisting torque force. These combined stresses would grind away at Pluto primarily along its minimal principle axis of inertia (bulge line).
It appears as though north and south of this 24 degree circular stress zone, the ices are soft and primarily nitrogen not water ice
In 2010 a Chilean earthquake shifted the Earth's axis of rotation by 2.7 milliarcseconds (about 8 centimeters, or 3 inches) and caused the Earth's rotation speed to increase slightly. In 2004 the Sumatran earthquake shifted the Earth's axis of rotation by 2.32 milliarcseconds (about 7 centimeters, or 2.76 inches) it also caused the Earth's speed to increase. While these are not large changes in speed or axial shift they do demonstrate how collapsing land (via subduction) redistributes the mass of the Earth, changing the rotation speed, the axial tilt, its nutation (wiggle) and its precession (wobble).
SP is a 2 mile deep sunken basin. As SP collapses under gravitational torque stresses and the wandering tidal bulge, Pluto's mass distribution changes in turn inducing shifts in rotation speed around its barycenteric point which would need to be counter balanced by Charon's gravitational breaking force. The axis would also shift causing a twisting torque force. These combined stresses would grind away at Pluto primarily along its minimal principle axis of inertia (bulge line).
It appears as though north and south of this 24 degree circular stress zone, the ices are soft and primarily nitrogen not water ice
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I'm suggesting this is the cause and creator of SP. Pluto and Charon are in near perfect circular orbits and tidally locked, nevertheless, they wobble significantly and wiggle, as one wobbles it has to gravitationally drag the other along. |
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This energy level is strong enough to make near surface crustal nitrogen convert to a liquid (explosive triple point phase) during some points in their Milankovitch cycle but it is not strong enough to cause the rocky minerals to rise to the surface (previous page) but it is probably strong enough to separate the rocky minerals from the more volatile material causing the more dense stuff to sink inward.
Volatiles are a relative term as their volatility is dependent on temperature. On Earth, water is volatile but on Pluto it is the bedrock. On Pluto volatiles are those gasses that can become gaseous like N2, CO and CH4. Water ice is not really considered volatile at Pluto temps. Some degree of differentiation is very likely created by this process but even if a fully differentiated core has developed, its a cold dead core, its too tiny to be otherwise. |
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In other words, Pluto's rocky core didn't create Sputnik Planitia, Sputnik Planitia's formation through tidal flexing created whatever rocky core may exist.
Pluto's wobble and gravitational interaction with Charon sustains Sputnik Planitia as a stationary hot spot over which Pluto's crust is slipping in a SE to NW direction creating banding stripes
Pluto's wobble and gravitational interaction with Charon sustains Sputnik Planitia as a stationary hot spot over which Pluto's crust is slipping in a SE to NW direction creating banding stripes
Pluto's crust is slipping over this hot spot, same as we see on Earth.
The most significant difference between Pluto's hot spot and Earth's is that tidal flex from Charon is inducing much lower energy levels at SP. This fact is demonstrated by the absence of dark surface minerals expelled by cryovolcanism. On Earth, hot spots deposit minerals from deep below, on Pluto light weight volatiles are bubbling up from shallower layers. |
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- We know Pluto's poles wobble 24 degrees.
- We know its core is too small to be hot (well, I think I do).
- We don't see any subsurface dark black ejected minerals deposited on the surface.
- There are obvious banding stripes suggesting decoupled skin slippage.
- SP is directly aligned with Charon (stationary)
- SP is likely a stationary hot spot created by Pluto and Charon's 24 degree wobble creating a focused gravitational stress zone.
Milankovitch cycles and nutation wobble creating tidal flex is my best guess as to what currently drives the geology on Pluto. A previous elliptical orbital dance between Pluto and Charon along with spin down initiated these conditions at Sputnik Planitia but now the long and short term wobble combined with layered water ice compression forces and an eccentric orbit around the Sun creating radical weather shifts probably sustains the triple point state of nitrogen in turn driving the geology on Pluto.
Earth's wobble is only 2 degrees, it has settled down over the 4.5 Gyr since the Moon forming impacts (plural) occurred. If Pluto and Charon had been orbiting each other for as long as our Moon and Earth, I think their 24 degree wobble would be much less radical. This also suggests these processes on Pluto have occurred over a shorter time frame than 4 Gyr (my guess 0.7 - 1 Gyr). The small satellite's erratic behavior and albedoes further support this concept.
