Pluto Surface Observations 1: NH Post-Encounter Phase, 1 Aug 2015- 10 Oct 2015 Options

[nprev]

This topic will contain images & discussion of same as they arrive during the extended download period. Similar threads will be opened in coming months as required as acquired data & discussion proceeds.

[Habukaz]

I was intrigued by what appears to be 'cells' in Sputnik that have plenty of dark stuff covering them, making them appear very dark:



Then it struck me that almost all of them were adjacent to mountains (and none of them far from mountains). Many of the mountains look quite steep and probably undergo rockfall and similar erosion processes. On the top of the slopes, dark stuff could accumulate (or be produced) and subsequently get carried down to surrounding plains on Sputnik by e.g. rockfall. The sharp boundaries of the 'cells' would then, I presume, be a sign of topography - the 'cells' would either be concave or convex in shape with clear boundaries between them. The simplest explanation would be that the boundaries of 'cells' were elevated relative to them, acting like fences to trap the dark particles within the 'cells'.

Further north, the cells are larger, allowing the particles to be carried further away by wind and preventing them from saturating the 'cells'. In the process, the prevailing wind direction in the area is also revealed:

[Gennady Ionov]

I was intrigued by what appears to be 'cells' in Sputnik that have plenty of dark stuff covering them, making them appear very dark:

I think the bright surface of Sputnik - it's just a white frost, but dark "cells" - the same as the dark flow to the northeast from Sputnik. These are places where the frost has sublimated over the summer and drew partly transparent ice (but water ice, not solid nitrogen).
The density of the atmosphere is too low to wind could blow not quite large particles, but the picture looks like sublimation. Over the cliffs (due to turbulence), and on the hills sublimation going faster.

[Habukaz]

The density of the atmosphere is too low to wind could blow not quite large particles, but the picture looks like sublimation.

The winds at Triton were considered responsible for giving geysers there trails. As I understand it, the surface pressure on Pluto can reach similar values to Triton (although the exact numbers appear to be a hot topic with the earliest REX data).

[Gennady Ionov]

The winds at Triton were considered responsible for giving geysers there trails.

Geysers can produce very small haze particles, but particles produced by erosion should be larger...

[Habukaz]

The idea was not that the dark particles were created by erosion, but moved downslope by it; e.g. by hitching a ride on a falling rock. I am presuming that the dark stuff is a (relatively) thin layer covering parts of the mountains, not what they are made of (something the brighter exposed slopes agree with).

[JRehling]

My sense is that the production of this terrain was extremely kinetic, and things were moving pretty fast, not due to regular-occurring winds but to a single catastrophic blast, like the production of many water channels on Mars (and some on Earth). Accordingly, I'd interpret the "leeward" features as places where the patterns in the deposition reflect the explosion's interaction with terrain, more like rays forming around an impact crater than anything blowing in the wind.

[Habukaz]

My sense is that the production of this terrain was extremely kinetic, and things were moving pretty fast, not due to regular-occurring winds but to a single catastrophic blast, like the production of many water channels on Mars (and some on Earth). Accordingly, I'd interpret the "leeward" features as places where the patterns in the deposition reflect the explosion's interaction with terrain, more like rays forming around an impact crater than anything blowing in the wind.

So you think Sputnik and related mountains and features formed very recently? I don't see those wind streak-like features lasting many orbits around the sun without being part of an ongoing process.

[JRehling]

I don't see those wind streak-like features lasting many orbits around the sun without being part of an ongoing process.

You're supposing a lot. What if those features aren't wind streaks but are due to boulders bigger than a fist? They could last eons.

You're using the supposition that they're wind streaks to validate the idea that they're wind streaks.

Mind you, the absence of craters speaks to the relative recency of their formation. It wasn't eons ago. But we have no basis to conclude that these features are mere feathery deposits of dust.

[Habukaz]

You're using the supposition that they're wind streaks to validate the idea that they're wind streaks.

No, that is trying to interpret what exactly your theory/idea is, hence the question for clarification. You did not specify object/particle size at that point.

There are ways such dark trails could disappear over a relatively short period of time, even if we are dealing with trails of big rocks. For example, mission scientists suggested that the ices of Sputnik are flowing. I haven't seen any guesses or estimates on the velocities of this supposed flow, but unless they are really low in this area, trails would get bent out of shape and/or dissolve in a geologically short period of time.

In general, I do not see how one could expect the surface of a body of ice to preserve such patterns over longer periods of time. But if Sputnik just has a thin cover of ice (and e.g. the dark stuff is actually sitting on the ground beneath the ice), then things would be different. Again, I do not know which interpretations of Sputnik you are using in your analysis.

[JRehling]

In general, I do not see how one could expect the surface of a body of ice to preserve such patterns over longer periods of time. But if Sputnik just has a thin cover of ice (and e.g. the dark stuff is actually sitting on the ground beneath the ice), then things would be different. Again, I do not know which interpretations of Sputnik you are using in your analysis.

Crater ray systems can last for eons, and we don't know that this isn't similar to that, but produced by an internal explosion rather than an impact, which a much higher volume of ejecta.

The absence of smaller impacts on Sputnik means that it is certainly very new, no matter what the origin of it was – at least in terms of whatever the cratering rate is at Pluto. That means that whatever happened, it is either a one-time event that happened recently in those terms or a cyclically-repeating event.

But neither of those inform the details of how fine the substrate is that causes the differences in the "down-wind" direction of obstacles. It could be like powder, or it could be like boulders. Our resolution is far too poor to know yet.

In none of these cases do we have to suppose that wind at any time besides the last, potentially violent, emplacement of material was the agent making the streaks.