Can Tiny Planetoids with High Density Retain an Argon-Oxygen Atmosphere?

[yotta]

Main Question or Discussion Point:

How small can an astronomical body be with 1.6 Earth gravity, and still hold an argon-oxygen atmosphere?

I have an idea for the use of up-down quark matter, (udQM) as described in the theory of the "continent of stability" in atomic physics, to create planetoids that are tiny, but have relatively strong gravity due to their very high density. udQM allows almost unlimited atomic mass, which has some very interesting possibilities for a very advanced civilization, but quite a lot below the Dyson Sphere level of technology.

udQM is to be a "waste product" from another civilization using it to generate energy. If it's denser than necessary, then a lighter material will be used above a core made of it, resulting in the desired gravity on the surface.

The atmosphere is to be the mass of 1.25⨁ above any location on the surface, the gravity 1.60⨁, resulting in an atmospheric pressure of 2.0⨁, or somewhat less due to the rapid decrease of gravity above the surface. The atmosphere is to be 10% oxygen, 88% argon, and 2% all other gases, excluding helium, which would escape too quickly. Slow loss of atmosphere is OK, can be replenished up to 2% per Earth year.

Here's my idea for the smallest size to possibly hold the atmosphere described above: radius: 25.0 km, density: 2.24kg/cm^3, mass: 2.45^-5⨁, vol.: 6.04^-8⨁, surface area: 1.54^-5⨁, gravity: 1.60⨁, orbiting the smallest red dwarf star possible, but quiescent, flares almost nonexistent, semi-major axis ≈ 2,700,000 km, orbital period ≈ 80 hours, luminosity on surface ≈ 0.6⨁.

Is this realistic, or nearly so, or would the planetoid's gravity decrease too rapidly with altitude due to the inverse-square law of gravity, so that it would rapidly lose atmosphere? After all, hypothetically, if they managed to create a tiny body with a radius of only two meters with 1.6 Earth gravity, the gravity at the top of my head would be only a little above 0.4g, so this body would not be anywhere near able to hold an atmosphere.

For those unfamiliar with udQM, here's the paper describing it: Bob Holdom, Jing Ren, and Chen Zhang. "Quark Matter May Not Be Strange." https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.120.222001

Note: this is not to be construed to be proof of udQM, but is a theory of a new type of matter which might be able to be created or exist naturally, but has not been observed to exist at this time. This thread is about what an advanced civilization capable of creating artificial planets might do with udQM, were it to exist.

Getting back to the original question, what would be a ballpark estimate of the minimum size for a planetoid to hold an argon-oxygen atmosphere as described above, with atmosphere loss < 2% per Earth year?

 

[Ryan_m_b]

I don’t know the answer but just to throw it out there: if the hypothetical advanced civilisation is going to the effort of assembling its exotic matter waste into planetoids why not put some sort of roof on the world to keep the atmosphere in? I’ve seen this idea pop up in some SciFi but not a lot, it’s called “worldhousing” or “shellworlds” if there are multiple layers of habitable space.

 

[member 656954]

Is this realistic

I don't want to sound too glib, but who cares? would be my answer.

More seriously, most readers don't care about the degree of detail you've described, and unless you can just weave those planetary attributes into the narrative, writing a sequence with atmosphere and inclination is unlikely to be a compelling read.

Getting back to the original question, what would be a ballpark estimate of the minimum size for a planetoid to hold an argon-oxygen atmosphere as described above, with atmosphere loss < 2% per Earth year?

I get you may be working this out for plot / timeline management, but because planetary formation with udQM is not real, you may find it considerably easier to just nominate the attributes you want and use them as if they are real. And esp. because you have already noted, "udQM allows almost unlimited atomic mass" so the planetoid can be as massive as needed, whatever the size.

The thing to guard against is burning a lot of time calculating your way through world building problems that have no bearing on the story, so consider what you can just make up to allow you to keep writing.

(And I talk from experience, having recently spent months fussing around with orbital mechanics for my novel, only to find that when I read it end-to-end, the real-world physics was invisible!)

 

[member 656954]

Just a quick follow up, @yotta, that may be helpful. Peter Hamilton is a best selling sci-fi author and first class writer and I recalled his Fallen Dragon novel describes a planet being terraformed and most of the detail is anchored by how the planet compares to other ones being settled, with the only orbital content its distance from the sun and the whole sequence contained in a few paragraphs.

Hamilton writes very successful 'high tech' with speculative physics and advanced civilizations, and if you're interested in reading it, the passage is included in the Amazon Look Inside for the novel, it's Chapter 3 once you get past the "seeing a cloud" opening.

 

[yotta]

I don’t know the answer but just to throw it out there: if the hypothetical advanced civilisation is going to the effort of assembling its exotic matter waste into planetoids why not put some sort of roof on the world to keep the atmosphere in? I’ve seen this idea pop up in some SciFi but not a lot, it’s called “worldhousing” or “shellworlds” if there are multiple layers of habitable space.

Actually, I had in mind a rogue planetoid version, as well, with somewhat lower gravity, hundreds or even thousands of levels of living areas, an outer atmosphere to protect the shell surface from small objects, and the ability to deflect large objects. For really large objects, the planetoid could be moved out of the way.

Some people simply want to live outdoors, on a planet(oid) orbiting a star, so I wanted to imagine both possibilities, but probably not both in one story.

 

[yotta]

I don't want to sound too glib, but who cares? would be my answer.

More seriously, most readers don't care about the degree of detail you've described, and unless you can just weave those planetary attributes into the narrative, writing a sequence with atmosphere and inclination is unlikely to be a compelling read.

I get you may be working this out for plot / timeline management, but because planetary formation with udQM is not real, you may find it considerably easier to just nominate the attributes you want and use them as if they are real. And esp. because you have already noted, "udQM allows almost unlimited atomic mass" so the planetoid can be as massive as needed, whatever the size.

The thing to guard against is burning a lot of time calculating your way through world building problems that have no bearing on the story, so consider what you can just make up to allow you to keep writing.

(And I talk from experience, having recently spent months fussing around with orbital mechanics for my novel, only to find that when I read it end-to-end, the real-world physics was invisible!)

Because the concept of udQM planetoids is clearly not copyright-able, without a story to go with it, others might use it, too. This is clearly background, which I'd like to get right. This could be a precedent in sci-fi, a smaller thing than the Dyson Sphere.

I'm really curious about the ability of astronomical bodies to retain an atmosphere, udQM or not, under various conditions of temperature, proximity to larger bodies, etc., especially how Titan is able to retain a heavy atmosphere in such close proximity to Saturn.

udQM is not real now, but might become so in the not so distant future. It theoretically begins at A ≥ 300, and we're at A = 294 now.

World-building is to be a big part of my story. Not only the physics of it, but many of the sociological aspects, as well. For example, an Earth-sized planet is so large as to be very nearly impossible for anyone empire to take over, but on the other hand, having many groups leads to more and larger wars than would be the case with a smaller planet, or especially a planetoid.

 

[yotta]

Just a quick follow up, @yotta, that may be helpful. Peter Hamilton is a best selling sci-fi author and first class writer and I recalled his Fallen Dragon novel describes a planet being terraformed and most of the detail is anchored by how the planet compares to other ones being settled, with the only orbital content its distance from the sun and the whole sequence contained in a few paragraphs.

Hamilton writes very successful 'high tech' with speculative physics and advanced civilizations, and if you're interested in reading it, the passage is included in the Amazon Look Inside for the novel, it's Chapter 3 once you get past the "seeing a cloud" opening.

Sounds like a very interesting book, especially given that the reviews were all over the map. I'm a slow reader, so wouldn't want to take on one of his trilogies. I'm getting a used copy, so I'll get to see how he handles the physics and world building.

 

[snorkack]

The trivially simple way to estimate upward decay of gravity is just escape speed.
For an example with no exotic matter to assume:
Moon is mostly stone and has density 3,34 kg/l. 1/6 gravity of Earth and escape speed 2,4 km/s
Imagine that Moon had a core mainly of iridium - some platinum and gold impurities, little iron or nickel, and a thin stone crust upon the massive precious metal core. Density 6 times bigger, at 20 kg/l
6 times Moon´ s mass is more massive than Mercury but not as massive as Mars.
Moon at 6 times the mass would have surface gravity matching Earth. But smaller escape speed - ablout 5,8 km/s.
It would still be bigger than 5,0 km/s escape speed of Mars. And Mars has river valleys. For hundreds of millions of years, Mars had flowing water and must have had denser air than now.
A body with only slightly higher escape speed than Mars might hold on to atmosphere.

 

[member 656954]

Because the concept of udQM planetoids is clearly not copyright-able, without a story to go with it, others might use it, too. ... This could be a precedent in sci-fi, a smaller thing than the Dyson Sphere.

Okay, interesting motivation. Did you know that Alastair Reynolds wrote a similar concept in Revenger, and even Dyson was elaborating on an idea Olaf Stapledon described in a 1937 novel when he mused on his sphere in his 1960's paper? Writing a novel for the purpose of 'owning' a concept is a lot of work and you're not guaranteed to be recognized for it. Besides, it costs to fight people you feel have stolen your ideas, esp. one with precedence.

All that aside, it is really hard to write an engaging novel laden with facts and figures that describe and explain your world building.

...but on the other hand, having many groups leads to more and larger wars than would be the case with a smaller planet, or especially a planetoid.

Not sure I'd want to live on a planetoid like that, but again, read Revenger because it's really hard to write a unique concept in science-fiction and this one at least has many siblings. Your mechanism for a dense, small object might be uncommon, but the idea certainly isn't. Which is why I always come back to asking, "What is the emotional tale you want to tell?" People read novels for the engagement. If they want facts and figures, they read textbooks. The world building should only ever be whatever you need to hook the reader and drive the plot. If you're writing mainly for the world building, it's typically a hell of a cliff to climb to capture reader interest.

 

[yotta]

The trivially simple way to estimate upward decay of gravity is just escape speed.
For an example with no exotic matter to assume:
Moon is mostly stone and has density 3,34 kg/l. 1/6 gravity of Earth and escape speed 2,4 km/s
Imagine that Moon had a core mainly of iridium - some platinum and gold impurities, little iron or nickel, and a thin stone crust upon the massive precious metal core. Density 6 times bigger, at 20 kg/l
6 times Moon´ s mass is more massive than Mercury but not as massive as Mars.
Moon at 6 times the mass would have surface gravity matching Earth. But smaller escape speed - ablout 5,8 km/s.
It would still be bigger than 5,0 km/s escape speed of Mars. And Mars has river valleys. For hundreds of millions of years, Mars had flowing water and must have had denser air than now.
A body with only slightly higher escape speed than Mars might hold on to atmosphere.

Even the Moon is huge next to the tiny bodies I'm talking about, so I'm not altogether clear that escape velocity and the ability to hold an atmosphere are as straightforward in my case.

I've done a few very simple calculations of what the gravitational strength would be at various altitudes, according to the inverse square law of gravitational attraction. Starting with 25 km, one radius above the surface, which is two radii above the center, the gravitational strength is 1/4 of what it is on the surface, or 0.4 Earth gravity. At 75 km, three radii above the surface, four above the center, it's 1/16 of what it is on the surface, or 0.1 Earth g. At 175 km, seven radii above the surface, eight above the center, it's 1/64 of what it is on the surface, or 0.025 Earth g.

This looks to me like borderline acceptable atmospheric retention, given the ability to replace slow losses there.

 

[member 656954]

I'm getting a used copy, so I'll get to see how he handles the physics and world building.

Hamilton's physics are entirely speculative, though he has some common aspects, such as wormholes, in most of his stories. Even his first novel, the kinda hard sci-fi Mindstar Rising, has extrasensory perception (ESP) and that's not even physics! But he rarely gets into the details of how the stuff works, he just presents it as working and focuses on what the consequence is for the characters.

His world building, however, is phenomenal. Hamilton is one of the few true 'space opera' authors around, populating his stories with huge casts, scores of planets, and macro-to-micro level detail. Honestly, I don't know where he finds time to write this stuff, he has to have a database to keep everything in check, and given how long most of his work is, he's like the Steven King of sci-fi, publishing big, bold, and eminently readable novels on a regular basis.

 

[yotta]

Okay, interesting motivation. Did you know that Alastair Reynolds wrote a similar concept in Revenger, and even Dyson was elaborating on an idea Olaf Stapledon described in a 1937 novel when he mused on his sphere in his 1960's paper? Writing a novel for the purpose of 'owning' a concept is a lot of work and you're not guaranteed to be recognized for it. Besides, it costs to fight people you feel have stolen your ideas, esp. one with precedence.

All that aside, it is really hard to write an engaging novel laden with facts and figures that describe and explain your world building.
Not sure I'd want to live on a planetoid like that, but again, read Revenger because it's really hard to write a unique concept in science-fiction and this one at least has many siblings. Your mechanism for a dense, small object might be uncommon, but the idea certainly isn't. Which is why I always come back to asking, "What is the emotional tale you want to tell?" People read novels for the engagement. If they want facts and figures, they read textbooks. The world building should only ever be whatever you need to hook the reader and drive the plot. If you're writing mainly for the world building, it's typically a hell of a cliff to climb to capture reader interest.

I didn't say I'm writing an entire novel for the sole purpose, or even main purpose, of establishing a precedent, nor the I'd consider myself to have sole copyright ownership of the idea of an udQM very dense body. Perhaps I wasn't entirely clear, I'm writing about it for now, as background for using it in my novel, and I'd put a more detailed description of the physics of it into an appendix at the end, not in the main story, which would bog it down.

In "Star Maker," Olaf Stapledon was talking about dead white dwarf stars after billions of years cooling off enough to allow life on them, which are quite different from my proposed udQM bodies. I didn't know about Dyson and dense bodies, because his sphere was to enclose an already-existing, naturally formed star, capturing and using 100% of its energy output, which to me bears no similarity at all to my udQM dense body idea.

Alastair Reynolds's concept of small dense bodies in Revenger sounds interesting, so I've ordered it, along with Peter Hamilton's "Fallen Dragon," which talks about terraforming. Both will be informative for me in my writing.

Even if very dense bodies which in all other respects are exactly the same except for being made of udQM have been written about before, my idea for them to be made of udQM is new and unique, and this discussion of them on this forum is precedent enough. As I said, because the concept of udQM planetoids is clearly not copyright-able, without a story to go with it, others probably will use it, too. Likewise, I'll want to make sure I'm not unintentionally plagiarizing anything, that my udQM planetoids are different enough to not be mistaken for any other author's ideas. I'd put them orbiting a different star, as double planets orbiting each other, or some such.

I'd probably have better luck if I came up with some trademarked name for my udQM planetoids, which I'd definitely do if I ever get my novel ready for publication. That's a long way off, since I really don't have any well-developed ideas, other than the part about udQM planetoids, some of which might be "rogue," or not orbiting any star.

I've a few early-stage ideas, such as extending humans' physical senses, such as increasing the range of hearing, and seeing into infrared and ultraviolet. I don't know what drama I'd have, because, on the one hand, I realize that some sort of conflict or dilemma is required for a good story, but on the other hand, I just want to write about happy, pleasant things. Unfortunately, the settings I'd want to actually live in and the ones that make a good story are radically different. One exception: I might not have this dilemma writing about the opposing goals of two or more groups of people.

 

[yotta]

Hamilton's physics are entirely speculative, though he has some common aspects, such as wormholes, in most of his stories. Even his first novel, the kinda hard sci-fi Mindstar Rising, has extrasensory perception (ESP) and that's not even physics! But he rarely gets into the details of how the stuff works, he just presents it as working and focuses on what the consequence is for the characters.

His world building, however, is phenomenal. Hamilton is one of the few true 'space opera' authors around, populating his stories with huge casts, scores of planets, and macro-to-micro level detail. Honestly, I don't know where he finds time to write this stuff, he has to have a database to keep everything in check, and given how long most of his work is, he's like the Steven King of sci-fi, publishing big, bold, and eminently readable novels on a regular basis.

I like the idea of "hybrid" hard and soft sci-fi, as in everything physical obeys the laws of physics, or nearly so, but then there can be ESP, astral travel, etc., but not reincarnation, since that infringes too much on religion; as if the godlike abilities of some alien species weren't infringement enough.

 

[member 656954]

I'd probably have better luck if I came up with some trademarked name for my udQM planetoids, which I'd definitely do if I ever get my novel ready for publication.

Color me confused, @yotta. You raised copyright now you're raising trademarks. Depending on where you are registering your trademark, it can be expensive and you are advised to hire an intellectual property attorney to handle the submission, but protection of fiction in this way seems murky and I'm not sure what you expect to gain from it?

That aside...

I don't know what drama I'd have, because, on the one hand, I realize that some sort of conflict or dilemma is required for a good story, but on the other hand, I just want to write about happy, pleasant things.

Even children's stories typically have some element of 'dark side', so you are spot on that conflict or dilemma is needed. But you can make that as simple as a protagonist finding their way in some endeavor and having their path blocked by adversity. It does not need to be unhappy or unpleasant, the challenge itself makes the protagonist unhappy but resolving that makes them happy.

Still, without even a concept, it's hard to provide any useful advice, apart from debating the physics of atmosphere retention for speculative udQM spherical bodies, and you can make that up and nobody will know...or care. Readers are there for the story. You need to write a consistent story, but emotional engagement wins over physical accuracy every time.

 

[yotta]

Color me confused, @yotta. You raised copyright now you're raising trademarks. Depending on where you are registering your trademark, it can be expensive and you are advised to hire an intellectual property attorney to handle the submission, but protection of fiction in this way seems murky and I'm not sure what you expect to gain from it?

That aside...
Even children's stories typically have some element of 'dark side', so you are spot on that conflict or dilemma is needed. But you can make that as simple as a protagonist finding their way in some endeavor and having their path blocked by adversity. It does not need to be unhappy or unpleasant, the challenge itself makes the protagonist unhappy but resolving that makes them happy.

Still, without even a concept, it's hard to provide any useful advice, apart from debating the physics of atmosphere retention for speculative udQM spherical bodies, and you can make that up and nobody will know...or care. Readers are there for the story. You need to write a consistent story, but emotional engagement wins over physical accuracy every time.

I didn't know trademarks were anywhere nearly that complicated, so I'm not going to want to go through that much trouble.

Good advice, that a challenge in a story need not be nearly as dark as almost all Hollywood movies have been in recent years. Good stories usually require an action to be taken, and/or an item acquired, in order to accomplish an objective, and there must be sufficient chances of it being unsuccessful, to make it interesting.

 

[member 656954]

Good advice, that a challenge in a story need not be nearly as dark as almost all Hollywood movies have been in recent years.

The film industry does seem to reflect the Geist der Zeiten, as researcher Bo McCready's 'Film Genre Study' showed last year. So, we'll probably see virus movies soon and depression ones after that

But stories don't need to be dark, that's true. One category where positivity is common is 'young adult' because the challenges can just be lifestyle, fish-out-of-water oriented, they don't need to be violent or horror based (though to be fair, a lot of stories adopt those themes). I'm writing a YA novel - which might pivot, I'm possibly too cynical for the age range - and it's fun not to have to elaborate the sci-fi elements quite as deeply as my Egan Universe books have needed to. It makes the writing faster, I'm already quarter way through and it's only May