APOD: 50 Miles on Pluto (2015 Jul 16)

Comments and questions about the APOD on the main view screen.
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BMAONE23
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by BMAONE23 » Sat Jul 18, 2015 3:16 pm

Could the apparent fact of Little cratering on Pluto/Charon be utilized as an argument in favor of Pluto Planet hood, Demonstrating that Pluto/Charon have in deed swept their neighborhood clear of debris? (Another one of the PLANET qualifications would be met) Then, relabeling it as Binary Planet PLUTO/CHARON rather than just Pluto places the Barycenter back within the boundary of the mass rather than outside the mass of Pluto :mrgreen:

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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by Chris Peterson » Sat Jul 18, 2015 3:35 pm

BMAONE23 wrote:Could the apparent fact of Little cratering on Pluto/Charon be utilized as an argument in favor of Pluto Planet hood, Demonstrating that Pluto/Charon have in deed swept their neighborhood clear of debris?
No, because it hasn't cleared its neighborhood. Its orbital zone includes multiple KBOs. Indeed, on most bodies, cratering is a better indicator of clearing their neighborhood than a lack of cratering!
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by ta152h0 » Sat Jul 18, 2015 5:30 pm

if a body slams into Pluto, does it melt the iceand then refreezes, for a brief period and " hides " the cratering ?
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by neufer » Sat Jul 18, 2015 6:42 pm

ta152h0 wrote:
if a body slams into Pluto, does it melt the ice and then refreezes,
for a brief period and " hides " the cratering ?
  • That sounds like an excellent suggestion to me, Wolf :!:
(And the chunks of ice that avoid melting become icebergs that are the observed mountains :?: )
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by Chris Peterson » Sat Jul 18, 2015 7:50 pm

ta152h0 wrote:if a body slams into Pluto, does it melt the iceand then refreezes, for a brief period and " hides " the cratering ?
I doubt it. The energy of impacts is generally too high to produce more than a little local melting. Most of the material would be vaporized or pulverized and ejected. Depending on the size of the impact, some would escape Pluto and some would settle back down as an ejecta blanket. So there would be nothing to fill in the crater- most of that material would have been removed.
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by neufer » Sat Jul 18, 2015 11:03 pm

Chris Peterson wrote:
ta152h0 wrote:
if a body slams into Pluto, does it melt the ice and then refreezes, for a brief period and " hides " the cratering ?
I doubt it. The energy of impacts is generally too high to produce more than a little local melting.
Most of the material would be vaporized or pulverized and ejected.
The Kuiper belt is basically all rotating in the same direction so Pluto (average orbital speed = 4.7 km/s) is likely to be involved with collisions of just a few km/s. I tried to work out a radioactive scenario but the heating is just way too low for such a small body.

Low speed Kuiper belt impacts must be major the source of heating, IMO.
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by Chris Peterson » Sat Jul 18, 2015 11:48 pm

neufer wrote:
Chris Peterson wrote:
ta152h0 wrote: if a body slams into Pluto, does it melt the ice and then refreezes, for a brief period and " hides " the cratering ?
I doubt it. The energy of impacts is generally too high to produce more than a little local melting.
Most of the material would be vaporized or pulverized and ejected.
The Kuiper belt is basically all rotating in the same direction so Pluto (average orbital speed = 4.7 km/s) is likely to be involved with collisions of just a few km/s. I tried to work out a radioactive scenario but the heating is just way too low for such a small body.

Low speed Kuiper belt impacts must be major the source of heating, IMO.
I'll reserve judgment on that one. It doesn't seem plausible to me that this could constitute a major source of heating. But that's beside the point, which was simply that cratering events don't cause melting, they cause ejection of material. The lowest speed impact possible on Pluto is 1.3 km/s, and while this is less than the speed of sound in ice, it is nevertheless going to result in a significant ejection of material, not a temporarily liquid lake which will freeze over leaving no evidence of the impact. I expect that most impacts would result from scattered disc bodies, not KBOs, and therefore the speed range will be wider, extending above the speed of sound in ice in many cases. Whatever is resurfacing Pluto, I doubt it is impacts.
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by neufer » Sun Jul 19, 2015 12:18 am

Chris Peterson wrote:
neufer wrote:
Click to play embedded YouTube video.


The Kuiper belt is basically all rotating in the same direction so Pluto (average orbital speed = 4.7 km/s) is likely to be involved with collisions of just a few km/s. I tried to work out a radioactive scenario but the heating is just way too low for such a small body.

Low speed Kuiper belt impacts must be major the source of heating, IMO.
I'll reserve judgment on that one. It doesn't seem plausible to me that this could constitute a major source of heating. But that's beside the point, which was simply that cratering events don't cause melting, they cause ejection of material. The lowest speed impact possible on Pluto is 1.3 km/s, and while this is less than the speed of sound in ice, it is nevertheless going to result in a significant ejection of material, not a temporarily liquid lake which will freeze over leaving no evidence of the impact. I expect that most impacts would result from scattered disc bodies, not KBOs, and therefore the speed range will be wider, extending above the speed of sound in ice in many cases. Whatever is resurfacing Pluto, I doubt it is impacts.
  • Anything big enough to punch through Pluto's nitrogen ice crust
    is going to make quite a splash in a ~140 km thick Plutonian ice slushy ocean.
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by Chris Peterson » Sun Jul 19, 2015 5:17 am

neufer wrote:
  • Anything big enough to punch through Pluto's nitrogen ice crust
    is going to make quite a splash in a ~140 km thick Plutonian ice slushy ocean.
Indeed, if Pluto has such a thing. I'll reserve judgment on that, too.
Chris

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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by ta152h0 » Sun Jul 19, 2015 7:17 pm

There was a recent posting that imaged the Pluto=Charon waltz that would indicate feature erasing tidal forces ? I mean, you got two heavy dudes dancing with each other and they are each a non rfigid body, I think
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Re: APOD: 50 Miles on Pluto (2015 Jul 16)

Post by Chris Peterson » Sun Jul 19, 2015 8:10 pm

ta152h0 wrote:There was a recent posting that imaged the Pluto=Charon waltz that would indicate feature erasing tidal forces ? I mean, you got two heavy dudes dancing with each other and they are each a non rfigid body, I think
With respect to one another, they're not dancing at all. They're mutually tidally locked, so neither sees any change in tidal forces from the other. Each is tidally deformed by the other, but that deformation is static. So there's no mechanism for heating or providing energy to drive tectonics.
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