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Pluto System Speculation
Explorer1
post Jul 19 2015, 08:03 AM
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How long after the Triton flyby did it take until images with the geysers came down? Data rates weren't that much better from Neptune in 1989, were they?
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squirreltape
post Jul 19 2015, 09:00 AM
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QUOTE (Paolo @ Jul 19 2015, 08:53 AM) *
Mike Brown (aka @plutokiller) had a couple of interesting tweets yesterday on the subject of Pluto being geologically active:


That is interesting. The assumption I'm led to here is that in order to explain the lack of cratering that implies a youthful, geologically active surface, some other method is required, namely the redistribution of frosts / ices that is prominent enough to obscure the cratering-record. Add in the lower chances of collision in the E-K Belt and the much lower collision energy (1 to 2 kms-1) then maybe frosts would do it.

But what of the atmosphere loss over time implying continual (or sporadic, ongoing) re-supply? Or are we seeing the last gasps and thin veneer of a primordial reservoir, however unlikely the odds?

I wonder how the water-cooler conversations explain these issues and which choice between geologically active and non-geologically active pleases Occam the most?


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ZLD
post Jul 19 2015, 01:35 PM
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QUOTE (John Broughton @ Jul 18 2015, 10:33 PM) *
...Tombaugh Regio lies inside what l think is an impact basin roughly 800km wide.


This is an interesting idea and I think theres a few elements that could lend itself to supporting it. However, I think the biggest reason this can't be the case is the lack of cratering. If that size of impact occurred, I would highly expect a ring system to form and as it condensed back to the surface, there would be many many impact craters. This would also deposit mixed elements across the surface and would leave few uniform looking areas, especially as large as Tombaugh Regio.


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stevesliva
post Jul 19 2015, 03:14 PM
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QUOTE (ZLD @ Jul 19 2015, 09:35 AM) *
This is an interesting idea and I think theres a few elements that could lend itself to supporting it. However, I think the biggest reason this can't be the case is the lack of cratering. If that size of impact occurred, I would highly expect a ring system to form and as it condensed back to the surface, there would be many many impact craters. This would also deposit mixed elements across the surface and would leave few uniform looking areas, especially as large as Tombaugh Regio.


A palimpsest basin opposite the sub-Charon point is possible, given all that.
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Sherbert
post Jul 19 2015, 05:34 PM
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If we consider the Tombaugh region is the result of an impact, possibly from a de-orbitting moon, the energy and pressure during the impact is going to convert vast amounts of frozen volatiles for a short period of time into slush, liquid and gas that flows out of the impact basin. How far they flow would depend on their viscosity and how quickly they refreeze. This differentiation in their distribution should show up in the Alice and Ralph data more explicitly, but the lower resolution false colour images already gives a good idea that this is the case. I have borrowed Bjorn's excellent map to illustrate (see post 902 of the main NH Near Encounter thread).

https://www.flickr.com/photos/124013840@N06...eposted-public/

The green circle is the outline of the proposed impact basin. It is pretty obvious.

The purple outline shows the area of serious surface deformation and resurfacing from the impact event and it's aftermath.

The red circles show possible impact craters, which could be from secondary ejecta impacts.

The yellow area is the approximate area of Carbon Monoxide already highlighted by the team.

The blue lines outline the areas where other volatiles liquified during the impact have flowed away from the crater. (Roughly the pale blue/cyan coloured parts of the false colour image.)

A de-orbiting moon should hit very near the equator, but the tidally locked Charon creates a slightly deeper gravity well above the centre of the green circle and so this would slightly change the velocity of the moon and drag it just slightly north of the equator. Others might know better, but this small influence would only occur very close to the surface of Pluto, causing the object to scrape a South to North furrow just before impact, the cone of the ice cream. I have no idea if this sort of intuitive scenario is actually plausible, but thats my two cents worth.

Although I tend to favour the moon or large mountain sized impactor, I don't rule out the impactor being Charon either, scraping past the surface. It could be that only Charon's tenuous atmosphere actually contacted the surface initially to create the furrow and then a tiny patch, a few square kilometres, of Charon's surface actually contacted Pluto at the impact site, where the super heated atmosphere and flash sublimated volatile ices, cushioned the impact and "bounced" Charon away from the surface significantly altering its trajectory. I still have difficulty in believing that Charon was then captured, but there may be a small set of solutions that allow it, so I am still keeping an open mind until we see more of Charon's North Pole.
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John Broughton
post Jul 20 2015, 03:53 AM
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QUOTE (ZLD @ Jul 19 2015, 01:35 PM) *
This is an interesting idea and I think theres a few elements that could lend itself to supporting it. However, I think the biggest reason this can't be the case is the lack of cratering. If that size of impact occurred, I would highly expect a ring system to form and as it condensed back to the surface, there would be many many impact craters. This would also deposit mixed elements across the surface and would leave few uniform looking areas, especially as large as Tombaugh Regio.

The curving scarps I circled would be the basin's outer rim. It is equivalent in size relative to Pluto that Mare Imbrium is to the Moon. Mare Imbrium also has an incomplete rim and no trace of inner rings, after being flooded with lava when the floor rebounded. Moderate-sized craters on Pluto can be made out despite having been blanketed under a kilometre or so of ice deposits, but there are none inside Tombaugh Regio. However, there appears to be craters west of that area that haven't been blanketed, particularly on the upper half of the whale's head. If Pluto ever had a thick atmosphere, there could be signs of its effects on the surface in high-resolution images of that region.
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serpens
post Jul 20 2015, 04:23 AM
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QUOTE (Paolo @ Jul 19 2015, 08:53 AM) *
Mike Brown (aka @plutokiller) had a couple of interesting tweets yesterday on the subject of Pluto being geologically active:
'In current hallway conversations with planetary scientists most are unconvinced by the evidence that "Pluto is geologically active"'


Yes, I can see a lot of tectonic changes taking place before the system became tidal locked but once tidal energy dissipated the surface should have been stable. While just one possibility, the mountain in a moat does does seem akin to the remnant of a collapsed tidal bulge. One thing I had forgotten and was reminded of in an old Dobrovolskis paper on the Pluto Charon binary system was that tidal dissipation would also cause the equatorial planes of the two bodies to realign to the [edit] orbital plane. The tidal bulge would become static as distance between the bodies increased but probably well before Charon became completely tidal locked, So after collapse it would potentially be displaced from the equatorial plane - just like the mountain in a moat. Yeah sheer speculation on my part but probably less speculative than geological activity or impact to explain the strange topography of the mountain in a moat. The upper bounds of the time taken for tidal locking for the system seems to be in the region of 100 Mya so the tidal locking is not in any way an indication of extended age and associated expectation of extensive impact craters.
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Bill Harris
post Jul 20 2015, 05:55 AM
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Sad, but anticipated.


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marsbug
post Jul 20 2015, 11:11 AM
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QUOTE (serpens @ Jul 20 2015, 05:23 AM) *
... The upper bounds of the time taken for tidal locking for the system seems to be in the region of 100 Mya so the tidal locking is not in any way an indication of extended age and associated expectation of extensive impact craters.


I didn't quite follow that Serpens, do you mean that tidal locking could have occured within the last 100,000,000 years and so the surface was being reshaped within that time, hence the surface is stable now and yet relatively craterless? That would place the formation of the Pluto/Charon system relatively recently, would it not?


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Mongo
post Jul 20 2015, 12:46 PM
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QUOTE (serpens @ Jul 19 2015, 05:09 AM) *
If as seems highly likely, Charon accreted from debris following a major collision [...].


I don't see this. There are so many example of large moons (half of the top ten KBOs by diameter have at least one) that for them all to be the result of a rare giant collision event is extremely unlikely. It's far more likely that large moons are a natural result of the KBO formation process in the low-energy environment of the outer Solar System, with each large KBO the "primary" of its own planetary accretion disc, from which large moons form in situ. Given the great distance from the Sun and the low planetisimal density, it seems likely that many of these KBO accretion discs would remain undisrupted until the large moons have coalesced (about half the time, going by the observed statistics).
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serpens
post Jul 20 2015, 01:47 PM
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All I am saying Marsbug is that if the Pluto - Charon binary system formed following an impact then the time from impact to tidal locking in the current configuration would have taken a comparatively short time in relation to the age of the solar system. When such formation occurred is an unknown but most of the surface features seen could readily be attributed to tidal and rotational deceleration tectonic processes and the lack of cratering does imply a reasonably short time since tectonics/resurfacing and dissipation of tidal heat. It actually doesn't matter whether formation of the system was due to impact or simultaneous accretion. The same roche limit, conservation of angular momentum considerations would apply.
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marsbug
post Jul 20 2015, 02:02 PM
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Thanks mate, that's clearer. I agree.


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Bill Harris
post Jul 20 2015, 05:43 PM
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Actually all of this is quite evident when you consider that the equatorial ice-field of Tombaugh Regio is an admixuture of variously CO2, CO, CH4, N2 or Ne and the organic refractory compound thiotimoline, which was likely introduced into the Pluto-Charon system by a passing Kuiper belt Chronoid body during the last age of Aquarius. By adding even trace amounts of thiotimoline to silicate minerals and refractory organics entrained in the gas flow, plus any desublimated dihydrogen monoxide also entrained.it allows workarounds around the various laws of Geology such as Uniformitarianism, Superposition and Superimposition. This get around some problems in the explanation of how younger strata can be emplaced below older strata. But since the exact properties of thiotimoline are not well-known under the conditions near this disputed planetary system, especially at the always-in-darkness cold trap in the South polar region, the actual effects on the geochron timeline is not well-constrained.

An idea of what could be found can be gained by reading "The Endochronic Properties of Resublimated Thiotimoline", I.Y. Ozimov, 1948, Campbell Press, with recent supplemantal material in http://danm.ucsc.edu/~phoenix/danm203/thiotimoline.pdf

Remember, there are no catastrophic processes, only catastrophic events. Sometimes things just go SPLAT.

--Bill
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mchan
post Jul 20 2015, 09:38 PM
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smile.gif

I, for one, would welcome a point-by-point rebuttal of the earlier posts within forum rule 2.1.
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serpens
post Jul 20 2015, 10:49 PM
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Hardly seems worthwhile mchan. Best to ignore the science fiction/fantasy world of Isaac Asimov's thiotimoline.
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