This is the North Eastern edge of Pluto where a series of expansion fractures have created a feature referred to as a spider.
It seems the land ice is under stress from below and has relieved that stress by creating long vertical fractures along with short horizontal cracks which merge into this central zone called the spider.
The fractures running south turn westward through the uplands/wetlands and eventually connects with Sputnik Planitia.
This Sleipnir Fossa crack eventually wraps from the north eastern side of Pluto southward into the wetlands migrating west into Sputnik Planitia traveling northwest through SP finally connecting to Inanna and Dumuzi Fossa traveling through the dried basin Piri Planitia and joining with a long vertical crack called Djanggawul Fossae.
More detail on page 28.
In the below image I have used a blue line to draw from the Spiders fractures how these cracks connect from one side of Pluto to the other.
I can't see under the fluid at SP but I can see where large fractures exit the western and eastern sides of SP.
I have connected the two sides of SP where these fractures enter and/or exit the basin.
Funny thing, yesterday 2/11/2016, I posted my theory of the fractures underneath Sputnik Planitia (SP). Today I noticed, NASA came out with this map of Sputnik Planitia yesterday as well,
Initially, I thought this was a map of the fractures under the nitrogen flow at SP but after paying closer attention to what NASA actually said, this is instead a map of the surface with its many cellular mounds with the trough patterns outlined in black lines.
NASA describes these as convection cells behaving something like lava lamps.
If they are convection cells then my theory about these troughs reflecting subsurface cracks is wrong. If they are not convection cells then my theory about them may have some validity to it.
One fairly obvious observation is the cellular patterns are mostly larger nearer to the center of SP and are smaller nearer to the edges.
They then fade into a flattened surface without troughs but with a higher density of sublimation cups.
Shallow sections of SP (nearer to land ice) tend to be devoid of troughs (not always) but have an increased quantity of sublimation cups.
Medium depth areas produce small cellular mounds bounded by troughs.
Deeper areas (farthest away from land ice) create large cellular mounds bounded by troughs with fewer sub cups.
The sublimation cups tend to decrease in size and quantity the further away they are from trough lines.
Cracks & Troughs
This is the north eastern side of Sputnik Planitia.
I drew yellow lines over the visible fractures in the land ice and then drew red lines over the troughs and red tholin swirls in the nitrogen liquid.
This seems to indicate that the troughs are in fact depressions in the fluid that match the fissures or fractures in the land below the fluid
Bottom line for me is that I am confused by the surface of SP. I've tried to see patterns in it that would explain its processes but after a year and a half I am still baffled by its surface. Lets break it down, perhaps this will lead to a conclusion.
Certainly there must be some form of viscous relaxation taking place in order for objects to impact the surface then disappear sorta like quick sand swallowing an object except in this case it's more like slow sand or as Alan Stern describes it the nitrogen ocean has a toothpaste consistency.
In this image you can see how there are troughs creating cells. To suggest that viscous relaxation is the cause of this surface is to ignore these troughs. Some process is creating them.
If you look close at this image one thing that seems to be taking place regularly is the more aggressive looking sublimation cups seem to cluster around the troughs. while further away from the troughs the sublimation cups tend to lighten up significantly.
The more sublimation taking place the more likely it is these areas are warmer than the areas with less sublimation cups.
Central parts of the cells are not smooth but the sublimation process appears to be significantly subdued compared to the zones around the troughs.
Sometimes an area without a clearly defined trough will have aggressive sublimation pits which seem to be turning into a trough but not quite there yet.
Sometimes the heat that makes the sublimation pits is strong enough such that the surface near the most aggressive pit formation becomes completely smoothed over. In other words, the fluid is so warm it can't even retain the shape of the sub cup.
More or Less
This is the general idea.
Areas with more pits tend to line up near areas where troughs exist or seem to be about to form.
It seems as though the aggressive action of the pits precede the formation of the troughs.
This suggest heat is welling up at these "More pits" spots which in turn forms the troughs.
In other words, the troughs are the byproduct of their alignment with a source of heat from below indicated by the sublimation cup's size and quantity.
Enceladus orbits Saturn every 33 hours while Dione orbits exactly twice that. This puts Enceladus and Dione in an orbital resonance.
Which causes extreme tidal flexing on the interior rock of Enceladus as well as the ice crust.
The tidal flexing creates heat which separated out the rocky material from the icy (watery) material. The heavier rock drops to the center creating a core where volcanic vents developed. That heat is released through the Tiger Stripe cracks. These cracks are the hottest place on Enceladus.
When they are stretched open the subsurface water ejects into space creating the outer E ring of Saturn.
I think this process is similar to regelation. Regelation is the process by which a substance melts under pressure and refreezes after the pressure is released.
Increased pressure decreases the melting point of ice and I assume the same holds true for nitrogen. If the fluid nitrogen at SP is 10 km thick, it will create an increased pressure on the bottom layer of nitrogen.
At depth the nitrogen would also be insulated further encouraging it to liquefy. Combine that with any available heat energy and since liquid nitrogen is less dense than frozen nitrogen (opposite to water) it would seek to rise to the surface in turn creating sublimation cups and cracks aka troughs.
The cracks running through SP seem to have formed under collapsing conditions then as we migrate out of SP to the west the cracks are once again expansion fractures.
Above and below the area called Viking Terra are a set of cracks running horizontal.
Viking Terra is a bulge in the land as subsurface pressure have distended it creating the fractures.
This seems to imply that either the land needed to bulge outward to accommodate the collapse of SP or SP collapsed as a consequence of the land bulging outward to the east and west.
I think the more likely of these two scenarios is that the one event of Sputnik Planitia's collapse caused the land on either side to bulge upward fracturing the land ice.