Pluto: The Big Picture – Convection, Evaporation, Flooding, Global Banding & Rotational Fission

Pluto the big picture
8. The pattern of global banding runs almost vertically in this image. (It’s about 10° clockwise from vertical). I conclude that this pattern is most likely the result of Charon’s formation by fission from Pluto.

convection cell enh1. The movement of soft ices in convection cells is carrying warm ice onto Pluto’s surface. This ice evaporates while moving to the edge of each cell, supplying Pluto’s atmosphere with nitrogen, methane and carbon monoxide. At the edge of each cell the soft ice, now cold, is subducted back into Pluto’s interior. The methane and carbon monoxide in the air react in sunlight, form hazes and eventually fall back to coat the ground in sticky gunk.

Some Glaciers Eastern Lobe Tombaugh Regio labeled(blue) with shoreline 12sep152. The last remnants of ice from a massive flood of soft ice that created the right side of Pluto’s ‘heart’, otherwise known as the right lobe or eastern lobe of Tombaugh Regio, is now flowing back into Sputnik Planum via a number of multi-mile wide glaciers. A large fraction of the flood ice, perhaps most of it, evaporated into the atmosphere. The greenish-blue color of the right lobe is due to one component of the soft ice that doesn’t evaporate as easily and is left behind like the skin that forms on top of a saucepan of hot milk. The same thing is happening where soft ice is evaporating on Sputnik Planum but before the skin of greenish-blue less volatile ice can build up it is subducted at the edges of convection cells and replaced by fresh sandy colored ice in the middle of each cell.

Sputnik Planum south pitted texture detail3. The southern lobe of Tombaugh Planum is the site of another massive soft ice flood. Here too remnant ice is flowing back into Sputnik Planum. The southern arm of Sputnik Planum is greenish-blue, like the southern and eastern lobes of Tombaugh Regio, because convection has stopped here. So the top layer of the low volatility component is not recycled. Debris outlining dead convection cells show that convection was previously active here too.

The suggestion has been made that the soft ice of that is poring off the eastern and southern lobes of Tombaugh Planum was deposited there by storms, like snowstorms on Earth (e.g. Hal Weaver of the New Horizons Team, at 42′ 53″, in his Space Telescope Science Institute talk of Oct 6) in his . However the immense quantities of ices that were needed to cover these immense areas are just too Norgay Montes flyover frame2 annotatedgreat to have been transported by weather. Floods are the only plausible mechanism to bring that much ice to such large but well defined areas.

The only way for flooding to have occurred is if the crust under the eastern and southern lobes of Tombaugh Regio buckled downwards so that Sputnik Planum ice could flow over them. This implies that Pluto’s crust is thin, flexible, strong and floats on an internal sea of soft ice like that exposed on Sputnik Planum.

Cracks on north Sputnik Planum shore4. Sputnik Planum’s soft ice is now in the process of flooding over the surface to its north, so here Pluto’s crust must be sinking at the very same time it is rising up at the eastern and southern lobes of Tombaugh Planum. Cracks opening up in the crust, along the northern shoreline are due to the downward buckling of the crust.

al-Idrisi Montes crust slabs pluto color 5. Iceberg like blocks of Pluto’s crust, ‘crust-bergs’, have washed up in clusters along Sputnik Planum’s western shore. The New Horizons team has named them as mountain ranges because The big crust-bergs are around 10 km to 30 km wide, but range up to 130 km across. They are ~5 km thick. These are fragments of a section a Pluto’s crust that was shattered thereby allowing the warm ices of Sputnik Planum to emerge onto Pluto’s surface. This section of crust may have been shattered by an asteroid impact or it may have broken up due to an internal cycle of heat build up and release. A darkening of the ice across Sputnik Planum probably marks the edge of the hole, now submerged.

Viking Terra healed hole (via Alan)
Looking west.

6. The fact that Pluto has such a thin crust floating on an ocean of warm (relatively speaking) ice explains why so much of Pluto’s surface is fairly crater free. As has happened recently, sections of the crust break up and are eventually replaced with new crust. The new crust forms due to the rain of sticky hydrocarbons primarily derived from the methane and carbon monoxide evaporating from Sputnik Planum. In times when their are no open areas of ice, which is likely to be most times, the gases would be released into the atmosphere via geysers or volcanoes, like those south of Norgay Montes. These volcanoes are dormant now because all of the pressure has been released via Sputnik Planum.

Cthulhu+Venera healed hole from mercator
Thick crust (left) supports deeper craters with higher rims. Crater rims sink and craters flatten where the crust is newer and thinner (right).
Elliot flooded craters
Elliot crater contains the faded remnants of an evaporated soft ice flood, earlier than those of the eastern and southern lobes of Tombaugh Regio.

7. The larger sizes and greater depth of craters in places like Cthulhu Regio shows that here the crust is old and thick enough to resist being broken up by bigger impacts. Even so, Cthulhu Regio does have some prominent cracks. These might have been made by the earlier soft ice flood that carried the crust-bergs to the western side of Sputnik Planum and deposited the ice of the C-shaped lake in the bottom of Elliot Crater. The remnants of this flood no longer have the bright greenish-blue color of the more recent floods because enough time has passed for it to get covered in a film of sticky hydrocarbons that have settled out of the sky.

Pluto north+western stripes
The impression of linearity (with bands running diagonally in this view) is particularly clear in this quadrant of Pluto’s surface to the north and west of Sputnik Planum. Similar parallel banding is visible over much of Pluto’s surface.

8. The surface features of Pluto give a distinct impression of linearity when seen from above Sputnik Planum. The impression is clearest when Pluto is viewed in black and white and appears to be come from a pattern of pattern of banded geology that underlies the surface features of Pluto.

I conclude that the pattern is most likely results from the  stretching of Pluto’s surface due to rapid rotation followed by its relaxation to a sphere after the fission of Charon and subsequent orbital evolution due to tidal interaction.

The relative orientations of Pluto and Charon at the time of their fission.
Pluto and Charon’s alignment at the time they separated (fissioned). Charon carried away a piece of Pluto’s ancient crust. On Pluto Charon’s launch site healed over with a cap of new smooth crust, while at the opposite end of Pluto the old crust crumpled to become the snakeskin and chaotic terrain beyond.

This model also appears to explain the origin of the folded ‘snakeskin’ terrain and the chaotic terrain further to the east.

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