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

[Nafnlaus]

Looks like a stitching error - not a big deal.

[ZLD]

Not sure what that is. It exists in the original file though.



I don't know enough about MVIC to be able to say what type of artifact that would be. Definitely peculiar.

[Bill Harris]

Think of this: consider the area of a sphere with the radius of the Kuiper Belt. And consider that even with a very low density of planetoids, given the area of the sphere there are potentially hundreds or even thousands of Pluto-, Charon-, Eris- or Sedna-class objects in existence. Greatly outnumbering the population of the terrestrial or gas-giant planets. So the conditions we are seeing at Pluto and Charon are to be considered the norm, and our rocky sun-huggers are the anomalies.

My esoterica for the month...

--Bill

[Herobrine]

ZLD: I see an shift in color that follows a straight line, a bug somewhere?

The published image is rotated ~48.6 degrees from its original orientation (+/- some 90-degree increment). The line you're talking about would be exactly horizontal if you rotated it 48.6 degrees counterclockwise, so it's most likely a strip boundary in the data. There are also others, but that one is the most noticeable in the image. The strip stands out like a sore thumb in LAB color space.

[alan]

I was looking at this before being distracted by the banding.



My eyes want to see part of a circle, mostly buried/eroded impact basin?

[MarkG]

In the past I've run into papers describing N2 eutectics with methane, carbon monoxide, and neon - the former two whose spectrums have been seen with the nitrogen in Sputnik (AFAIK neon hasn't been detected on Pluto). Neon significantly lowers the triple point temperature (as its triple point is lower), while one of the former two (I forget which one) allows one to have liquids at a mildly colder than pure N2 when a small amount is mixed in (although the triple point is still rather warm by Pluto standards). I'm sure if you google you'll find the papers yourself.

Really, though, it wouldn't take too much internal heat at all to boost the temperature 10-20 degrees; you've got an insulating ice cap, and radiative heat loss is proportional to T^4, so it drops to extremely low rates at cryogenic temperatures. If the heat is there then there should be liquids dozens of meters under the surface at Sputnik - you have your heat, you have your pressure... it's what should happen. But whether said heat is actually there and whether there actually are liquids, I'm not going to speculate.

Seasonal mass re-distributions from sublimation/condensation would generate small perturbations that might efficiently couple to internal heating due to the large tidal locking regime (non-intuitive relaxation forces). And the presence of a subsurface phase-change layer being perturbed could generate some tectonics.

Also, if N2 ice is really that weak, multi-year frost accumulations could "flow" down and erode terrain (ice rocks) in such a way as to give fluvial-like patterns, especially as seen from the photo altitudes.

The bottom of my jaw is still getting rug burns....

[Explorer1]

Think of this: consider the area of a sphere with the radius of the Kuiper Belt. And consider that even with a very low density of planetoids, given the area of the sphere there are potentially hundreds or even thousands of Pluto-, Charon-, Eris- or Sedna-class objects in existence.

Mike Brown's blog post made me a lot more pessimistic when I first read it: http://www.mikebrownsplanets.com/2015/01/t...rs-of-eris.html
True, lack of bright objects does not mean lack of any objects. But would things that large have been found by now, if they're anywhere closer than the Oort?

[ngunn]

What does it take for water ice to be exposed? I would suggest two things: one, recent movement, meaning recent compared with the timescale of tholin gunk deposition, the other the presence of water ice close to the surface (millimetres) meaning no deep deposits of something else. Some places in the red zones might fit these criteria but the red stuff itself doesn't have to be ice.

[fred_76]

A little artistic experiment with Photoshop and the three images of Pluto, Charon and Pluto's blue haze over a Milky Way background :

[Bill Harris]

True, lack of bright objects does not mean lack of any objects. But would things that large have been found by now, if they're anywhere closer than the Oort?

To me that means that it's a very large piece of real-estate with a lot that hasn't been discovered yet. Discovering "edna" and friends was only the beginning...

--Bill

[HSchirmer]

Even in a perfect vacuum with no type of volatile transport at all, wouldn't one expect exposed water ice to sublimate away until a sufficient insulating layer of it's impurities to prevent sublimation covers the surface?

Not at these temperatures, H2O is not volatile. It is, eh 230 C/K degrees below the freezing temperature.
For a comparison, thats around the difference between earth temperature and the melting point of aluminum.
Would you expect an aluminum can to sublimate away?

However, there are some papers that discuss how volatile ices with impurities, (on pluto N2 and CH4 as volatiles, perhaps tholins or H2O grains) , tend to form a crust of non-volatiles which blocks vaporization

[Req]

Thanks for clearing that up for me. So can it be assumed that bombardment from highly energetic particles would be the process that provides the highest(and also a reasonably well-measured and understood) constraint on possible time for surface ice to be exposed and detectable by NH on Pluto? Can anybody ballpark what that figure might be?

[Nafnlaus]

Mike Brown's blog post made me a lot more pessimistic when I first read it: http://www.mikebrownsplanets.com/2015/01/t...rs-of-eris.html
True, lack of bright objects does not mean lack of any objects. But would things that large have been found by now, if they're anywhere closer than the Oort?

It depends on what you want to call "bright". Increase the distance by 1.4x and you halve the light coming across it. Double the mass of a body and you only less than 1,6x its cross sectional area. And the difference between a bright albedo and a dark one can be a more than 20fold difference in reflected light.

Current estimates are that despite having found well over 1000 KBOs with diameter greater than 100km we've only found about 1% of them. NEOWISE did a good job ruling out large gas giants within 10k AU, but Neptune-sized bodies could exist well closer and undiscovered Mars or even Earth-sized bodies in the vicinity of the Sednoids, let alone Pluto and Eris-sized bodies. And more to the point one of the main theories to explain the orbits of the Sednoids is a large rocky object orbiting well beyond the orbit of Neptune.

I'm so excited for LSST, and I hope it stays funded through completion. It has the potential to find essentially all bodies greater than 100km in the Kuiper cliff, and countless larger objects further out (such as Sednoids and potentially whole new families). There's going to be such a vast wealth of data coming in from it, I can't wait to see it. It'll also find 80-90% of potential earth-crossing asteroids greater than 100m diameter in its baseline case, and should be able to find well over 90% after refinement.

Too bad it's such a long time between "discovery" and "probe" :Þ I particularly want to see one to Haumea, that has to be a fascinating world.

[HSchirmer]

So can it be assumed that bombardment from highly energetic particles would be the process that provides the highest
... constraint on possible time for surface ice to be exposed and detectable by NH on Pluto?

Interesting question, given the recent images of haze layers, and the look-back image's "morning mist" at the terminator,
I'm beginning to think that tholin dust might be faster acting than radiation aging.

[HSchirmer]

What does it take for water ice to be exposed?
I would suggest two things: one, recent movement, meaning recent compared with the timescale of tholin gunk deposition, the other the presence of water ice close to the surface (millimetres) meaning no deep deposits of something else. ...

Some other things to add to that list -
You could have rock-hard water ice as "dust particles", somewhat like the rust dust all over Mars.
Could have H2O clathrates of N2 or CH4 or CO, if they warm up the volatiles sublimate and leave H2O behind.
Some papers on N2 ices describe a "fracture front" where bulk N2 ices shatter when they experience the a-b crystal phase change around 35 K.
Consider a bulk layer of N2 ice frozen onto the slope of a H2O mountain, when the N2 ice warms and shatters, it ought to expose a fresh H2O surface.