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#1 2026-05-05 17:36:00
- tahanson43206
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Kuiper Belt Objects - Generic Topic
We have four topics that contain the word "Kuiper" but none seemed appropriate for posts about discoveries about Kuiper Belt Objects as they occur. This topic is available for NewMars members who might wish to contribute to a store of knowledge about Kuiper belt objects. We will lead off this series with a report of a thin atmosphere around an object that was thought to be to small to support one.
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#2 2026-05-05 17:37:27
- tahanson43206
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Re: Kuiper Belt Objects - Generic Topic
This post is reserved for an index to posts that may be contributed by NewMars members.
Index:
Post #3 will provide a CNN report on a Japanese discovery of a thin atmosphere around a Kuiper belt object.
Post #4 SpaceNut List of important Kuiper belt objects:
https://newmars.com/forums/viewtopic.ph … 72#p239172
Post #5: Calliban - Wikipedia article on discovery of atmosphere
http://newmars.com/forums/viewtopic.php … 82#p239182
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#3 2026-05-05 17:38:29
- tahanson43206
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Re: Kuiper Belt Objects - Generic Topic
This post is about discovery of a thin atmosphere around a Kuiper belt object thought to be too small to retain one.
https://www.cnn.com/2026/05/04/science/ … atmosphere
Astronomers find atmosphere around a solar system object that shouldn’t have one
ByAshley Strickland
Updated 22 hr ago15
An artist’s impression shows (612533) 2002 XV93 passing in front of a background star. Ko Arimatsu/NAOJAstronomers have detected a thin atmosphere around a tiny celestial body in the outer solar system for the first time — an object previously thought to be too small to support the presence of an atmosphere.
Thousands of frozen, rocky bodies called trans-Neptunian objects, or TNOs, exist in the Kuiper Belt on the edge of our solar system, remnants from its formation 4.5 billion years ago.
The dwarf planet Pluto is the largest of these TNOs, so named because they’re found beyond the orbit of Neptune.
The frigid temperatures and weak surface gravity of the small bodies has long caused astronomers to believe they aren’t capable of retaining atmospheres — with the exception of Pluto, which has a thin one. Atmospheres, especially dense ones, typically form around large planets or moons, including Saturn’s biggest satellite, Titan.
Meanwhile, dwarf planets Eris, Haumea, Makemake and dwarf planet candidate Quaoar, the largest TNOs after Pluto, don’t appear to have atmospheres.
During a rare observation opportunity, astronomers in Japan spotted the thin shell of an atmosphere around a TNO known as (612533) 2002 XV93, according to a study published Monday in the journal Nature Astronomy.
While Pluto has a diameter of 1,477 miles (2,377 kilometers), 2002 XV93 only spans about 311 miles (500 kilometers) across.The unexpected discovery — made by Dr. Ko Arimatsu, associate professor and senior lecturer at the National Astronomical Observatory of Japan, and his colleagues — could offer an unprecedented glimpse into how an atmosphere forms and remains around a small object, and change how astronomers think about objects in the Kuiper Belt.
Seizing the observation opportunity
As January 2024 neared, Arimatsu and his colleagues prepared for the unique chance to observe a TNO as it passed in front of a bright star, as seen from Japan.
2002 XV93 has a standard orbit for a Kuiper Belt object and is smaller than a dwarf planet, so it wasn’t considered to be different from other TNOs.
But such moments when a TNO is illuminated by a star in the cosmic background, called stellar occultations, are rare opportunities to study the size, shape and features of a small, distant object, Arimatsu said. The researchers set up at three different locations across Japan, using observatories in Kyoto and the Nagano Prefecture, as well as a citizen scientist-run telescope in Fukushima.
The star’s light gradually faded as the TNO moved in front of it, suggesting the presence of of an atmosphere. If an object has no atmosphere, a star disappears and reappears much more sharply.
An animation shows how gradually starlight fades when passing behind a celestial body with an atmosphere (top), as opposed to an object without one. NAOJ / Shingo Iwashita
“The observation data showed a smooth change of the star’s brightness near the edge of the shadow, lasting about 1.5 seconds,” Arimatsu wrote in an email. “This kind of smooth brightness change is naturally explained if the starlight was bent by a very thin atmosphere around the object.”
The researchers calculated that 2002 XV93 has an atmosphere about 5 million to 10 million times thinner than Earth’s — and suspect two possibilities as to what created it.
The atmosphere could be the product of cryovolcanoes on the small, icy body, which release internal gas such as methane, nitrogen or carbon monoxide from beneath its surface. Or, another Kuiper Belt object such as a comet might have struck 2002 XV93, also releasing gases from the subsurface.
Arimatsu’s team is continuing the search for atmospheres around other TNOs by relying on stellar occultation observations. Their findings could help determine if 2002 XV93 is a rare exception to the rule, or if other similar small objects also possess atmospheres.
“This was an exciting discovery to read about,” said Dr. Scott S. Sheppard, staff scientist at the Carnegie Institution for Science in Washington, DC. “It was thought that objects like 2002 XV93 would be too small to have an atmosphere, but this result shows that is not true.”
Sheppard did not participate in the research, but he has studied and discovered TNOs.
The finding also highlights the discovery of recent activity on 2002 XV93, Sheppard noted, whether it be the eruption of frozen gases or the aftermath of material slowly falling back onto the object’s surface.
“This shows the Kuiper Belt is not a cold dead place,” Sheppard wrote in an email, “but is teeming with activity and has many of the building blocks for life.”
Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
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#4 2026-05-05 18:20:55
- SpaceNut
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Re: Kuiper Belt Objects - Generic Topic
Here is the list of the Key Known Planetoids & Dwarf Planets, to which we are still looking for the gravitational calculation suggests there is a real large planet x (9) that is believed to orbit beyond to ort cloud.
Pluto: The largest and best-known Kuiper Belt Object (KBO), it is a complex icy dwarf planet with multiple moons.
Haumea: An elongated dwarf planet known for its rapid rotation and ring system.
Makemake: A large, reddish dwarf planet and one of the brightest objects in the belt.
Orcus: A large KBO that, like Pluto, is in a 2:3 resonance with Neptune.
Quaoar: A dwarf planet candidate that may possess a mountain taller than Olympus Mons.
Eris: While often categorized as a Scattered Disc Object rather than specifically in the main Kuiper Belt, it is a massive, icy dwarf planet, slightly more massive than Pluto.
Arrokoth: A remarkably pristine, two-lobed object (contact binary) visited by the New Horizons spacecraft in 2019
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#5 2026-05-06 08:06:12
- Calliban
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Re: Kuiper Belt Objects - Generic Topic
Interesting discovery of atmosphere on 2002_XV93.
https://en.wikipedia.org/wiki/(612533)_2002_XV93
This little world is just 470km in diameter and surface gravity is ~1% Earth normal. So even a thin atmosphere should dissipate quickly. The authors suggest complete escape in 100 - 1000 years, depending upon composition. The source of the atmosphere is most likely an impact exposing buried volatiles, which subsequently sublimate.
By my estimation, the escape velocity of this body is less than 200m/s. Even at the low temperatures present in the Kuiper Belt, I am surprised that an atmosphere could survive as long as 100 - 1000 years. The gases most likely to be present, N2, CO, CH4, also have relatively low molecular mass. If we take nitrogen as an example gas and assume an atmospheric temperature of 50K, the median gas molecule velocity is 177m/s.
https://cfm-calculator.com/calculator.p … ulator.php
That means that around half of the molecules in the atmosphere will be moving at velocity that exceeds escape velocity. How is it that these gases are not lost on a timeframe measured in hours or days rather than years? How could any atmosphere survive for centuries?
******
Additional: I think the reason that the atmosphere can hang around for so long is due to inertial confinement. The particles that escape first are at the top of the atmosphere, where the mean free path starts to exceed the scale height. The particles beneath are confined by collision with particles above them. This deflects them downward, confining them. Even so, it isn't clear to me why the lower layers wouldn't just expand, pushing the upper atmosphere into space. How escape can happen so gradually is not something that I can explain.
Last edited by Calliban (2026-05-06 09:27:07)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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#6 2026-05-10 15:53:20
- Calliban
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Re: Kuiper Belt Objects - Generic Topic
I believe that I have a partial answer for how the small body 2002_XV93 can hold an atmosphere for such a long period of time. I believe there are two reasons:
(1) Although the information available is sketchy, at temperatures beneath the critical point of a gas (126K for N2), molecules begin to stick together as van der waals forces begin binding them into clusters. If pressure remains beneath the liquidus point, these clusters never grow sufficiently large to allow nucleation. However, if gas molecules bind together into quasi-stable clusters, their average molecular speed will be reduced as per kinetic theory of gases. This reduces the proportion of molecules able to exceed escape velocity.
(2) Solar wind, although weak in the kuiper belt, preferentially ionises the upper region of the atmosphere 2002_XV93. This results in a voltage gradient between the top of the atmosphere and the ground. This results in an attractive electrostatic force between the upper atmosphere and surface of the planetoid.
I don't know if these factors were accounted for in estimating the atmospheric lifetime of 2002_XV93. If not, the atmosphere could persist for longer than was predicted. These factors may also help explain why the leakage rate of Pluto's atmosphere was 10,000 times lower than predicted.
In the past, we have discussed the possibility of creating thin atmospheres on smaller KBOs and dwarf planets to improve habitability. These findings, if they can be substantiated, improves the case for that. But clustering only works if the gases remain cold and van der waals forces dominate. This limits the scope of application for this technique.
This is interesting.
https://physics.stackexchange.com/quest … atmosphere
The first post suggests that a body with a radius >50km could retain an exosphere. I am going to put the jean's escape equations into a spreadsheet and see what the results are for different gases and temperatures.
Last edited by Calliban (2026-05-10 16:24:09)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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#7 2026-05-11 10:12:45
- Void
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Re: Kuiper Belt Objects - Generic Topic
Calliban,
>125 K???
For Triton, Pluto, Eris, then, energy of atmosphere is number of molecules in a gas state, and temperature at the surface. (I think).
I wonder if you could provide a good enough greenhouse method either gasses or particles, that you could evaporate more gas while not shining heat to the higher atmosphere?
The Greenhouse Pannikins for Earth say that indeed a strengthen greenhouse gas layer will cool the upper atmosphere.
So, for these Dwarf Objects, perhaps it would be possible to build up a 1 bar atmospheric pressure if you could increase the heating at the bottom of the atmosphere and lower the heat at the top of the atmosphere.
Then perhaps add a artificial magnetic field to make things even better.
So, on these worlds, if you want to radiate heat, you might only do it on the night side and try not to radiate ground heat to the sky in the day.
Easy to say, maybe possible ot do????
If you had fusion reactors perhaps. You might dump heat into water during the day, and then pump that water on top of an ice slab at night to freeze and cool at night.
Maybe can do.
Of course, even so due to the cold on the surface then you need enclosures with heated air inside and very good thermal insulation.
With fusion power then even rogue worlds the size of Pluto might be made to have a pressurized atmosphere. Of course they will have no day, so you would release the heat more evenly across time..
Ending Pending 
Last edited by Void (2026-05-11 10:24:53)
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#8 2026-05-13 02:14:03
- Calliban
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Re: Kuiper Belt Objects - Generic Topic
Void, I think you are correct. The bottom of the atmosphere should have a temperature around the boiling point of nitrogen at whatever the pressure happens to be, likely around 70K. The top of the atmosphere will be as cold as we can make it. Warmer gas at the bottom of the atmosphere will rise by convection. It will naturally cool as it expands. Any particulates it the atmosphere will also allow the gas to cool by radiation.
Pluto appears to have enough nitrogen to form a 20-30KPa surface pressure if enough artificial heat is injected at the surface. This would allow cities to be built beneath inflated tent or greenhouse structures, without need for pressure domes. Any ecosystem would still need to be very much artificial. The outside temperature is too cold and has too little sunlight to make natural ecosystems possible. But the atmospheric pressure would make it relatively easy to build large enclosures full of air, as there would be little or no pressure difference between the air inside and the atmosphere outside. The same would be true on Titan.
I had hoped to build a spreadsheet programme that could model the structure of the atmosphere. What is holding me up is the difficulty in finding information on the gas properties of nitrogen at temperature beneath its triple point at 63K. Whilst the bottom of the atmosphere will be warmer than this, the top will be colder. I may make a start with a model that assumes an isothermal atmosphere and see what it looks like.
Clustering of gas molecules beneath the critical point of a gas is a real phenomena. These clusters become nucleation points as the gas condenses into liquid. This happens in Earth's atmosphere and allows water vapour to condense into rain. There is surprisingly little scientific knowledge of how clusters form at the molecular level. But this has a significant impact on atmospheric escape, because clusters of nitrogen molecules will have reduced molecular speed compared to ideal gases. Clustering of gas particles will also make the atmosphere more compact. Clustering helps explain how very small KBOs are able to sustain tenuous atmospheres. If nitrogen behaved as a strictly ideal gas, this would have been lost to space very quickly. But the clustering of molecules reduces average molecular speed and reduces leakage. So even very small bodies can hold on to thin atmospheres for a surprising amount of time. But it only works at low temperatures.
Last edited by Calliban (2026-05-13 02:29:06)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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#9 2026-05-13 06:55:34
- Void
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Re: Kuiper Belt Objects - Generic Topic
Good post Calliban.
I recall internet materials that said Pluto may naturally achieve a 250 millibar atmosphere when closest to the sun. (25 Kpa).
I will guess that there may be more Nitrogen, entrained in crust, or as Ammonia ice or Ammonia in an underground ocean.
I believe I recall Carl Sagan saying that Titan just barely holds on to it's Nitrogen.
So, some hopes for Triton, Pluto, and Eris.
But what if you have a Methane cycle, and Tholen's?
I believe that light reflected from the surface of Mars may contribute to atmospheric loss. But Titan will reflect not as much visible or ultraviolet light, (I think). So, any attempt to expand an atmosphere on Triton, Pluto, and Eris, might include a Methane cycle, with reactors spewing out Methane gas, and radiation inducing an additional cloud deck.
This might allow for a warmer surface and a very cold upper atmosphere.
The brings me to the question of Aliens. If they have a technology with an energy source other than a star, might they prefer these little worlds?
A rogue Pluto would have virtually no star induced atmosphere loss. It may in fact accumulate Nitrogen from the Vacuum faster than it loses it.
Steppenwolf Planets need to be the size of Mars or larger it is said to accumulate a Hydrogen/Helium atmosphere.
A Plutoid Rogue, may not accumulate such an atmosphere, but it might have these molecules of Hydrogen and Helium accumulate a bit on top of a Nitrogen Atmosphere, (Provided sufficient surface heat to sustain a Nitrogen atmosphere).
Would these worlds accumulate cosmic dust?
Cosmic Dust and radiation may alter the nucleation process.
But it might accumulate in the surface ices where cryovolcanic eruptions do not cover it up.
After initial agrégation and possible differentiation, it may be that accumulations of cosmic dust may exist on the surface of rogue planets if they have a surface (Ices).
For Triton, Titan, and Pluto, perhaps the solar wind tends to reduce the amount of cosmic dust infall.
https://www.popsci.com/science/young-rogue-planet/
Quote:
Rogue planet is gobbling up 6.6 billion tons of dust per second
The cosmic oddities experience their own growth spurts.
Andrew PaulPublished Oct 5, 2025 2:15 PM EDT
Add Popular Science(opens in a new tab)
More information
So, Steppenwolf's would be one deal, and rogue Plutoids would be another.
If you found a rogue plutoid that had been around for billions of years and warmed up a Nitrogen atmosphere, then there may be significant accumulations of "Metals" in its surface layers, from cosmic dust and larger fragments.
Ending Pending
Last edited by Void (2026-05-13 07:18:44)
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#10 2026-05-13 18:36:02
- Void
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Re: Kuiper Belt Objects - Generic Topic
Here is an article which might appear to support some features of our conversation Calliban.
https://www.msn.com/en-us/news/technolo … r-AA236Lym Quote:
Scientists reveal why the Earth's upper atmosphere is cooling while the surface is heating up
Story by Shy Cohen • 8h •
6 min read
It remains to be demonstrated if aliens would prefer to stay out of deep gravity wells occupied by stars and some large rogue objects. But they may prefer to jump around on Steppenwolf and Plutoid worlds, in the deeps of space.
That is if they can come up with a good energy source.
Perhaps someday humans/robots from Earth may do that.
Ending Pending
Last edited by Void (2026-05-13 18:39:48)
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#11 2026-05-14 16:25:57
- Calliban
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Re: Kuiper Belt Objects - Generic Topic
Void, that is interesting. It suggests that we can likely build temperature gradients within the atmosphere.
I decided to build a spreadsheet to model the atmosphere of a body the same mass and diameter as Pluto. My assumption is that this body is far enough away from any star that the top of the atmosphere is dominated by non-ionised N2 at 40K temperature. The spreadsheet models the decline in pressure vs height using the standard scale height equation. This is based on ideal gas properties, which makes it pessimistic, as nitrogen gas will be more compressible beneath its critical point (126K). This will result in a more compact atmosphere with a higher escape velocity in the exobase. So any results calculated here will be bounding for real gases. My assumption is that the atmosphere is heated from the bottom, with little or no heat arriving at the top.
Some assumptions and starting conditions.
1. The model calculates atmospheric properties at increments of 100m and extends from the surface up to the exobase at 1242.8km.
2. The temperature at the surface is taken to be 68K, which is the saturation temperature of nitrogen at 28.481KPa. This is above the triple point for N2, allowing liquid N2 to flow on the surface. It is also a high enough pressure for human breathing, meaning that habitats will not need to be pressurised.
3. Temperature is assumed to be constant at 68K, until a height of 27.4km. At this point, pressure drops to 12.6KPa, which is the triple point pressure of N2. The assumption is that temperature declines to 63.2K at this point. Temperature remains constant w.r.t height until pressure drops to 10KPa at 34.7km. For pressures <10KPa, I was able to derive an equation for saturation temperature as a function of pressure, based upon the phase diagram for nitrogen. The fitted equation is:
Tsat ~ 7LOG(P/1.93E-5)
Using this equation iteratively, I was able to model a declining temperature vs height, reaching a temperature of 40K at 243km. Beyond this height, temperature is assumed to be a constant 40K until the exobase.
4. The local scale height was calculated using a value of g that was calculated using Newtons universal law of gravitation:
g = GM/((r+h)^2)
Where: g = gravity at height, h, above the surface; G = 6.67E-11; M = Mass of body (kg); r = radius of body (m); h = height above the surface.
The scale height was recalculated for each 100m element within the atmosphere.
Local escape velocity is given by: Ve = (2*g*(r+h))^0.5
Results
The main question that we wish to answer with this exercise is whether such an atmosphere could be stable for any length of time. For a body as small as Pluto, with an escape velocity of ~1.2km/s at ground level, is it possible to sustain an atmosphere with enough pressure for human breathing for a long timescale? This was the question I wished to answer.
The escape velocity at the exobase is only 846m/s. However, at a temperature of 40K, the root-mean-square speed of N2 molecules is only 189m/s, about 4.5x smaller than escape velocity. I used an online tool to calculate the Maxwell-Boltzmann distribution for N2 at 40K. Amazingly, only ~5E-7 of the molecules (i.e. 1 in 2 million) attain a speed of 846m/s. I conservatively doubled this number to estimate the integral of the curve at all speeds higher than this.
The mass flux escaping from the exobase can be approximated by multiplying the number density of escaping molecules in the exobase by their average escape velocity. The pressure at the exobase is 7.39E-9Pa. Solving the ideal gas equation gives a mass density of 6.23E-13kg/m3. Assuming 1 in 1 million of these has sufficient energy to escape, allows escape flux to be calculated:
q = (6.23E-13/1,000,000)*846 = 5.25E-15 kg/m2s.
Multiplying by the surface area of the whole atmosphere at the exobase (7.428E13m2) gives a whole planetary mass loss rate of 0.039kg/s. The total atmospheric mass is 9.18E17kg. It will therefore take 7.46 billion years to lose 1% of the atmosphere via Jean's Escape. I would therefore expect cosmic ray sputtering to be a more important atmospheric loss mechanism than Jean's escape. Suffice to say, the atmosphere should be stable over geological timescales.
Interesting facts:
1. Although the atmosphere is extensive, some 75% of its mass is within 50.2km of the surface.
2. The column density of the atmosphere (mass per unit of surface) is some 51,700kg.m-2. This is ~5x the column density of Earth's atmosphere, yet surface pressure is only 28% Earth sea level. This is a direct consequence of the low gravity of the body. It also suggests that building such an atmosphere is only likely to be achievable if the nitrogen is already in place at or close to the surface of the body and can be vaporised by adding heat.
3. Assuming all heat is radiated into space from the top of the triple point layer, the total radiant heat flux ejected into space is 1.7E13W, or 17TW. Present human civilisation uses some 19TW per year. So the terraformed world could support a large civilisation, but there are clearly limits to population and power consumption before waste heat becomes a problem. If we assume that the bulk of human food is produced via artificial photosynthesis, which turns electrical energy into calories with 20% efficiency, then providing 10MJ of food energy per day requires 50MJ of electrical energy. This in turn, would require the generation of 100MJ of heat in the powerplant. If we assume that each human needs an extra 1kWe for other (non-food) energy needs, then each human will need a continuous 3kWe of power production, implying some 6kWth of nuclear heat production. This implies a maximum practicable population of 2.83bn for this dwarf planet. That is 160 people per square km.
If human beings do find rogue Pluto sized bodies in interstellar space or the Oort cloud, it is possible in principle to terraform these worlds, at least from the point of view of providing surface pressure sufficient for humans to breath. Humans would still need to live within habitats that are hotter than the surface. But these could be thin tent like structures, as there would be no effective pressure difference between the inside of the habitat and the surface. Something like a polymer membrane draped over a steel frame, would be sufficient to separate warm breathable air inside, from cold nitrogen gas outside.
My next iteration of the spreadsheet will explore how small a world would need to be before this terraforming approach is no longer viable.
Last edited by Calliban (2026-05-14 18:24:49)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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