When I use the word fluid it is a relative term. My point in using the word fluid is to describe the relatively fast motion of one ice compared to the relatively slow motion of another ice hence one acts more like a fluid or liquid when compared against the same time scale of the other.
Pluto goes through Milankovitch cycles, it's poles wobble from 102 to 126 degrees creating extreme atmospheric conditions which sometimes allows Nitrogen to reach its triple point (become a liquid, solid and gas). In this video, Alan Stern (16 min mark) explains how Pluto has had atmospheric conditions due to Milankovitch cycles that would allow nitrogen to reach its triple point. |
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The red tholin material accumulates along the edges of the polygonal mounds in the area similar to the coffee ring effect.
In the below closeup image it appears as though waves have formed in the whiter yellowish material moving outward and the waves terminate along the border where the yellow material meets the red tholin covered material. The yellow material is moving away from the land ice while the red tholin material is moving toward the land. The waves seem to imply the yellow material is hotter hence less viscous than the red stuff. Since the red stuff is thicker or more viscous it sets up a boundary between it and the more fluid yellow material. |
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I know it may sound like it but just because I keep saying there were/are subsurface fluids running through this area shaping the landscape that doesn't mean I think there were no surface fluids at any point.
On Page 5, I postulated a theory about Piri Planitia suggesting that once it contained a fluid that flowed into Sputnik Planitia after Inanna and Dumuzi Fossa's joined the two planitias. Piri Planitia is a bit of an anomaly and not so easy to explain. An easy explanation is to say it was once filled with fluid then the fluid either sublimated away or it sunk back underground like a desert on earth or it drained via the Fractures or Fossa's into Sputnik Planitia all are possibilities. There is one other possibility, subsurface fluids eroded the underside of this land area eating away at it which created an impression as the fluid migrated underground. Is there any evidence to support that last supposition? |
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Look closely at the land area south of Piri Planitia. It looks peculiar and different than any other areas. It's puckered and wrinkled as if it is being affected by some process from below the surface. This makes me think there are some heat and perhaps chemical processes occurring below the surface chewing away at the land ice. |
Sometimes their center fully collapses but there is typically a ridge around the edges if the center collapses.
Even when they collapse flat they tend to have signs of the central pucker.
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Sometimes they collapse mostly flat.
These images suggest Piri Planitia is not a Pingo effect. If Piri Planitia were created like a pingo it would display a bulge upward then collapse downward it would tend to show a ringed outer ridge and pucker marks with a central collapsed zone. This is not what we see at Piri Planitia so no go on the pingo.
It could be a sink hole but they tend to have a nice round deep shape. I mostly agree with my friend about surface processes shaping Piri Planitia but the corrosion pattern to its south and the Viking terra bulge to the east give me pause. |
This image clearly shows how this whole area was once a fluid with ice blocks looking like sheets more than blocks. This is an extension of the processes that are taking place at SP. This area only recently cooled and hardened as the crater count is low but present. This land ice is likely thin as it is in the process of freezing. That is probably why the craters are typically shallow. Impactor's break through the ice leaving a ringed indent they look like muffled impacts. |