Landable (Semi) Habitable Planets... Are A Thing?

[Jumpin' Jack Flash]

Hi

It's not uncomon for tenuous-atmospheric worlds to hold deep craters. Very deep craters. I've surveyed several that go down 8-10km below the planet's surface, with a couple even further.
But, what do the numbers say? Let's take Swoilz AC-G b3-8 2 as an example. Its major dayside crater (located at 13 46 latitude/longitude) goes down to 8.5km... which, assuming I've done the numbers right, gives it a pressure of 20.7% pure oxygen. That's about equivalent to an actual Earth-Like's oxygen content, and it's got a quite habitable regional temp of 10-15C!

An interesting post!

So...if deep craters on planets in Elite (just for discussion) could harbour the beginnings of some form of new life (or new gameplay) other than what's available in the game now, I'm initially thinking of the more bio plant like stuff here, but then this could also lead on to include animalia etc...Are you suggesting that on some planets these 'pockets' of life restricted to deep craters would be a starting point for Frontier to introduce some more content along those lines, or are we in this sense restricting these pockets of life to mainly include present earth type flora & fauna, I include your 'normal' human lifeforms as well here.

The sticking point in all this though is, is it easier to expand the game this way, and do we at the same time ignore the other obvious question of why isn't the present 'habitable worlds' for example Earth and other terrestrial worlds be open to more on foot gameplay and other obvious (or expected) content, when deep craters and canyons are habitable.
The other way of looking at it is planets like Mars could be a testing ground for at least some form of planet based 'terraforming' in the game if deep craters and canyons were taken into consideration (or that topography created there for that purpose)?

I get the feeling though that introducing new life and game content, including more detailed Sol like system environments we can land on and interact with is an all or nothing scenario for Frontier, you could start it off in the Sol system though as I've suggested with Mars, that would be a fairly logical step I suppose. ...but I'm going off topic here so....

If I may ask...What do you think these deep craters (and canyons) could be used for (or contain) in the form of new gameplay?...we could all have entirely different viewpoints and ideas on this topic!
Another question...would these craters be created by a more crafted approach, that might lead to a more singular detailed feature, or would they be created with more like a procedural generation programming method?

Jack

 

[IstvaanDCIV]

I fly ships at 10+G with minimal grey/red out and survive landing on 40+ G planets. Whaddya mean we haven't been genetically improved?

I'm not sure if biology alone would provide the provide the level of enhancement required. My personal headcanon is that before going into space, all travellers get an injection of unobtrusive nanotechnology that reinforces capillaries, nerves, and other delicate structures to prevent them dying of strokes or embolisms and whatnot.

Presumably 34th century medicine also has an answer to the massive levels of radiation exposure like when we fly really close to neutron stars...

Just leaving this here:

"While there have been minor variations in the earth’s total oxygen level, over time humans and animals have become physically adapted to breathing air that contains approximately 21% oxygen.

Therefore, it makes sense that because humans and animals are adapted to breathing 21% oxygen in air, anything much different from 21% would be hazardous to our health. This is why OSHA considers any oxygen level below 19.5% as oxygen deficient or anything above 23.5% as oxygen enriched air. Both are potentially dangerous."

Oxygen Enrichment and Fire Hazards

Oxygen enrichment is the general term for any gas or liquid that has more than 21% oxygen by volume in the air. It increases the risk of fire in enclosed areas.

www.co2meter.com

But that's talking about oxygen percentages when overall atmospheric pressure is more or less equal to Earth's at sea level, isn't it? If total pressure is higher or lower, then oxygen percentages should be adjusted accordingly in order to maintain health. In the earliest days of the space race, they used high oxygen atmospheres at lower pressures in spacecraft. The reason they stopped was not because astronauts couldn't breathe it, but because it presented too great of a fire risk.

 

[Markov Chaney]

So what you are saying is, under the right circumstances/balance a “vacuum” (albeit not technically one if there is a layer of water vapor) could exist?

The layer of vapour can be lowwwww pressure. This phase diagram is from a study of Martian climate:

This is saying that at 250 degrees K (-23 C) (ie the left of the diagram) the equilibrium between ice and vapour is already down to under a millibar and there simply won't be any (stable) liquid water in that environment.

What about the ammonia biospheres though (one of the Titans even parked above such a ‘vacuum’ ammonia world in Col 285 Sector BA-P c6-18)?

Gotta love the first proper academic page I found starts with this: "Understanding the compressive behavior of ammonia ice is an enduring topic due to its salient implications in planetology and the origin of life"

Compressive behavior and electronic properties of ammonia ice: a first-principles study - PMC

Understanding the compressive behavior of ammonia ice is an enduring topic due to its salient implications in planetology and the origin of life as well as its applications in agriculture and industry. Currently, the most stable crystal structures ...

pmc.ncbi.nlm.nih.gov

I can't find an ammonia phase diagram with low temperature - low pressure on it, but here's a vapour pressure diagram:

(https://en.wikipedia.org/wiki/Ammonia_(data_page))
Below the "triple point" (about 200K and 60mbar) the equilibrium will always be between ice and vapour, again the liquid isn't stable down the bottom left of this phase diagram (or most phase diagrams). The 1 mbar equilibrium point is at 180K or so, so this isn't radically different to water.

You can also see this is the opposite behaviour of water on this part of the diagram because at the left hand edge of this diagram the curve has started to drop faster rather than slower which means the pressure trends downwards faster than for water. I guess that's to do with both water ice and ammonia ice being differently weird. It means that on a planet cold enough for an ammonia ocean to freeze out, the atmosphere is likely to be super-thin. OTOH it means if you want liquid ammonia sloshing around you need a good bit of atmosphere.

Because while the codex says the Thargoids can survive vacuum for some time, I’m not exactly sure that is a naturally evolved ability.

Bold of you to assume the Thargoids naturally evolved...

 

[aRJay]

I'm not sure if biology alone would provide the provide the level of enhancement required. My personal headcanon is that before going into space, all travellers get an injection of unobtrusive nanotechnology that reinforces capillaries, nerves, and other delicate structures to prevent them dying of strokes or embolisms and whatnot.

Presumably 34th century medicine also has an answer to the massive levels of radiation exposure like when we fly really close to neutron stars...



But that's talking about oxygen percentages when overall atmospheric pressure is more or less equal to Earth's at sea level, isn't it? If total pressure is higher or lower, then oxygen percentages should be adjusted accordingly in order to maintain health. In the earliest days of the space race, they used high oxygen atmospheres at lower pressures in spacecraft. The reason they stopped was not because astronauts couldn't breathe it, but because it presented too great of a fire risk.

Well NASA used that sort of atmosphere but the Russian programmes used air.

 

[galahad2069]

But that's talking about oxygen percentages when overall atmospheric pressure is more or less equal to Earth's at sea level, isn't it? If total pressure is higher or lower, then oxygen percentages should be adjusted accordingly in order to maintain health. In the earliest days of the space race, they used high oxygen atmospheres at lower pressures in spacecraft. The reason they stopped was not because astronauts couldn't breathe it, but because it presented too great of a fire risk.

Exactly.

 

[Shurimal]

Low pressure pure O2 is still used in EVA suits today.

 

[Neilski]

Nope, water worlds with counterintuitive water depth vs atmosphere depth is a thing; it basically depends what order of baking and freezing the geology went through when forming, and also how much ice is a factor. You just need a combination that is locally stable in the space of possibilities, which is not the same as "the one that makes the most sense."

Basically if there's too much liquid it will produce gas and if there's too much gas you'll lose it out the top of the atmosphere, sure, but the two things can happen at different rates and the rates are affected by different parameters so it doesn't necessarily meet in the middle of the problem space, it can end up in weird corners. And there's feedback because the heat at the water/vapour boundary depends on how much heat is rejected or trapped by the atmosphere before it reaches the liquid surface.

And less basically once you get down to two-figure temperatures the phase diagram for water is utterly weird because water is weird.

There's a good thread on this from months (years?) ago where we all really got into the physical chemistry of it.

Hmm, am not seeing how that works, but maybe I'm missing something crucial, assuming that we're both talking about water worlds with liquid water (let's say a temperature of a little over the triple point of water, to keep things simple). Water is indeed weird in multiple ways but I think the fundamental question here is still fairly simple.

As I see it, if you start with a water world with liquid water at let's say 280 K and no atmosphere, you don't (can't) have an equilibrium. The water near the surface will boil vigorously and create a layer of water vapour (while also cooling itself down, creating another non-equilibrium thing to consider!) and the pressure of that layer will increase. If you don't run out of water entirely, then you'll reach an equilibrium in which the (potentially much colder, maybe even frozen) surface water has a layer of water vapour directly above it, of which the pressure is exactly the vapour pressure of water at the same temperature as the surface water. Whether that equilibrium is a "long term" (billions of years?) or "short term" (millions?) thing depending on whether the gravity is high enough to retain the atmosphere is beyond the scope of this thought experiment
Have I made a booboo somewhere in this logic?

(I searched and found some Reddit threads on this topic but no forum threads; would be grateful for any links you or anyone knows about.)

NB: I have no clue how low the atmospheric pressure can be before ED labels a body as having "no atmosphere".

 

[Ian Doncaster]

NB: I have no clue how low the atmospheric pressure can be before ED labels a body as having "no atmosphere".

0.01 atmospheres, I think, is the lowest stated. Depending on how it rounds that might just leave a very narrow temperature range where liquid water is stable, looking at the triple-point diagram. Sufficiently narrow, of course, that it wouldn't be stable with temperature variation due to planetary rotation, though you might just about be able to get a setup where the surface was mostly frozen solid but the hottest bits formed shallow temporary liquid puddles as the planet rotated.

One other option which might work more plausibly
- the surface temperature is low enough that it's actually an ice world on the surface, at minimal atmospheric pressure
- there is some liquid water below that, close enough to the surface in places to be considered "ocean".
Europa-like, but bigger and with a thinner ice-crust.

 

[Kira Goto]

Europa-like, but bigger and with a thinner ice-crust.

Theoretically, those worlds already exist within Elite as the "Electricae" plant states that it is generally found near frozen lakes [on ice worlds], per the Codex. Of course, said lakes are probably not actually present within the game. (And those plants might not be a natural occurrence, but why someone would create and seed them is beyond me.)

 

[varonica]

Theoretically, those worlds already exist within Elite as the "Electricae" plant states that it is generally found near frozen lakes [on ice worlds], per the Codex. Of course, said lakes are probably not actually present within the game. (And those plants might not be a natural occurrence, but why someone would create and seed them is beyond me.)

The interesting thing about the electricae I found while on one planet was that they will be found on frozen bodies, yes, but there was an entire icy plain coloured blue but hardly any electricae to be found. The reason in the end was the plain was covered in a layer of snow with tiny and sparse ice patches with no snow, and it was only on those ice patches that the electricae appeared, never on the snow. So what I am assuming here is that in the simulation the snow area was either snow over rock or very think ice where the temperature was always low enough for the snow to not melt, and the icy patches were areas where there was liquid water close beneath the surface and the added heat from the water was causing the snow/ice to melt and refreeze into ice.

So frozen lakes in that situation does make sense, the water below the surface would be warmer and the electricae may be tapping into the warmer water and that is causing the snow to melt that then refreezes into ice, simulated of course because there's no actual water layer, but in that regard the info in the codex doers make sense if the electricae grow around frozen lakes with liquid water below.

 

[Tifu]

But that's talking about oxygen percentages when overall atmospheric pressure is more or less equal to Earth's at sea level, isn't it? If total pressure is higher or lower, then oxygen percentages should be adjusted accordingly in order to maintain health. In the earliest days of the space race, they used high oxygen atmospheres at lower pressures in spacecraft. The reason they stopped was not because astronauts couldn't breathe it, but because it presented too great of a fire risk.

Basically oxygen is a corrosive element that binds with almost anything - that's why iron and even steel corrodes and rusts in an oxygen rich atmosphere. It's just that our bodies and our planetary ecology has had millions of years to adapt - but only up to a point. Too much oxygen and our cellular membranes also begin to deteriorate (it's in the article I linked to above).

NASA originally wanted an oxygen-nitrogen mix but simplified that to pure oxygen - until the Apollo 1 disaster. After that, all space capsules while on the launch pad have an oxygen-nitrogen feed and only switched to oxygen-only after launch.

In a pure oxygen atmosphere, even that tiny spark that happens when you pull out your cell phone charger from an electric socket will be deadly. And I don't even want to imagine what wildfires are like on planets with very high oxygen concentrations

source: https://www.discovermagazine.com/the-sciences/why-apollo-had-a-flammable-pure-oxygen-environment

 

[Kira Goto]

So frozen lakes in that situation does make sense, the water below the surface would be warmer and the electricae may be tapping into the warmer water and that is causing the snow to melt that then refreezes into ice, simulated of course because there's no actual water layer, but in that regard the info in the codex doers make sense if the electricae grow around frozen lakes with liquid water below.

It does sound as if that is the case. The wording in the Codex is as follows -

Organisms found exclusively on extremely cold worlds in the vicinity of frozen lakes. The visible tips can be observed protruding from the ice, often near fissures where it is thinnest. The bulk of the organisms extend down through the ice into the subsurface melt, potentially for several kilometres.

Which matches up with my observation they usually only seem to pop up on ice rather than snowy surfaces. It also goes on to state they use "the thermal circulation of the surrounding fluid to drive an electrochemical process" and some other stuff about this being why they are only found in noble gas atmospheres (but not why they do this). The 'radialem' variant supposedly also often only occurs near nebulas, whatever the link to that may be. ("may have an unspecified link with the proximity of nebulae to its host planet)

 

[IstvaanDCIV]

Theoretically, those worlds already exist within Elite as the "Electricae" plant states that it is generally found near frozen lakes [on ice worlds], per the Codex. Of course, said lakes are probably not actually present within the game. (And those plants might not be a natural occurrence, but why someone would create and seed them is beyond me.)

Electricae being unnatural might not necessarily mean they were deliberately placed. They might have been accidentally propagated via their seeds clinging to the landing gear of Guardian ships. Or something like that.

 

[aRJay]

Theoretically, those worlds already exist within Elite as the "Electricae" plant states that it is generally found near frozen lakes [on ice worlds], per the Codex. Of course, said lakes are probably not actually present within the game. (And those plants might not be a natural occurrence, but why someone would create and seed them is beyond me.)

Because they are pretty?

Basically oxygen is a corrosive element that binds with almost anything - that's why iron and even steel corrodes and rusts in an oxygen rich atmosphere. It's just that our bodies and our planetary ecology has had millions of years to adapt - but only up to a point. Too much oxygen and our cellular membranes also begin to deteriorate (it's in the article I linked to above).

NASA originally wanted an oxygen-nitrogen mix but simplified that to pure oxygen - until the Apollo 1 disaster. After that, all space capsules while on the launch pad have an oxygen-nitrogen feed and only switched to oxygen-only after launch.

In a pure oxygen atmosphere, even that tiny spark that happens when you pull out your cell phone charger from an electric socket will be deadly. And I don't even want to imagine what wildfires are like on planets with very high oxygen concentrations

source: https://www.discovermagazine.com/the-sciences/why-apollo-had-a-flammable-pure-oxygen-environment

See episode 3 “Green” of Chris Packhams series Earth for the effects of too much O2.

 

[Markov Chaney]

Hmm, am not seeing how that works, but maybe I'm missing something crucial, assuming that we're both talking about water worlds with liquid water

I think my generalities mixed ice worlds and water worlds tbh, because everything I said in generalities about temperatures below 273K also assumed pressures under 1 atm ... so no liquid.

But the specific point about liquid / gas boundaries stands, see below.

(let's say a temperature of a little over the triple point of water, to keep things simple). Water is indeed weird in multiple ways but I think the fundamental question here is still fairly simple.

As I see it, if you start with a water world with liquid water at let's say 280 K and no atmosphere, you don't (can't) have an equilibrium.

Indeed. So you'll get an atmosphere of vapour, and everything else being equal, the water will stop boiling off when the sea level pressure hits only ~0.0227 atm (@ 293K because it was easy for me to find the figure for 20 deg C - it'll be a even less at your example temperature of 280K )

The question becomes how much atmosphere you need to stack under what gravity to hit that ~23 mbar pressure.

That's a pretty skinny atmosphere, so maybe the part that isn't obvious is how fast water's vapour pressure climbs with temperature, 'cos obviously at 373K it's one atmos ...

The water near the surface will boil vigorously and create a layer of water vapour (while also cooling itself down, creating another non-equilibrium thing to consider!) and the pressure of that layer will increase

That's OK, makes things easier, because the cooler that water-gas system gets, the lower the vapour pressure. So the latent heat effect actually helps bring down the size of atmosphere yo
you need.

If you don't run out of water entirely,

That is one of the "depends what order things happen in" factors, aye. Let's assume our terraforming goal here is to breed spherical cows...

then you'll reach an equilibrium in which the (potentially much colder, maybe even frozen) surface water has a layer of water vapour directly above it, of which the pressure is exactly the vapour pressure of water at the same temperature as the surface water.

Yes, we're agreeing here... but I guess you surfaced another "depends what order things happen in" assumption because this does indeed only work if you left yourself enough headroom in temperature to stop the water freezing.

One thing that helps prevent a runaway freeze is the second bunch of latent heat involved, the latent heat of fusion, suspect that means you would need really vigorous boiling to actually freeze it; more likely to get into chunks of slush (if it nucleates at all) and get stuck at triple point, or a supercooled state if it doesn't nucleate nicely.

Whether that equilibrium is a "long term" (billions of years?) or "short term" (millions?) thing depending on whether the gravity is high enough to retain the atmosphere is beyond the scope of this thought experiment
Have I made a booboo somewhere in this logic?

The only booboo seems to be you're talking like what you said makes it not possible at all, whereas actually you're relitigating what I said and calling out the assumptions needed to make it work.

(I searched and found some Reddit threads on this topic but no forum threads; would be grateful for any links you or anyone knows about.)

Previous me definitely went and found a paper on this which is what convinced me in the first place, but darned if I can find it again either!

0.01 atmospheres, I think, is the lowest stated.

That's in the sort of order of mag we were talking here...

Depending on how it rounds that might just leave a very narrow temperature range where liquid water is stable, looking at the triple-point diagram.

I gave up trying to figure it out looking at phase diagrams and just went with vapour pressures, plus the assumption some factors help it stop going in the direction of ice (see above)

Sufficiently narrow, of course, that it wouldn't be stable with temperature variation due to planetary rotation,

Yeah we should be talking ranges so add that to the big old pile o' assumptions. Particularly interesting to think about what might happen with runaway winters because that's definitely example where it might flip from a stable 293K-with-water over to 270K-with-ice. Particularly nasty because the freeze pumps heat into the atmosphere and the vapour pressure will drop significantly so at that point I suspect the atmosphere would be straight out the top of the gravity well. It wasn't exactly great when it happened on Earth and that was with a whole 1000mbar of atmosphere to stop it going properly wrong.

though you might just about be able to get a setup where the surface was mostly frozen solid but the hottest bits formed shallow temporary liquid puddles as the planet rotated.

Going back to the original question, A C Clarke's Imperial Earth claims that Titan looks like this, but methane.

In our scenario the question is what happens when a puddle hits 300K - it's not like it's going to superheat a column of vapour over it all of a sudden and a bunch of atmosphere escapes out the top; so this must be at least metastable.

Then again "what happens when the sun heats a bit of water unevenly" is "a tropical hurricane" we know that already.

One other option which might work more plausibly
- the surface temperature is low enough that it's actually an ice world on the surface, at minimal atmospheric pressure
- there is some liquid water below that, close enough to the surface in places to be considered "ocean".
Europa-like, but bigger and with a thinner ice-crust.

These here "sub-surface water" exoplanets have been a hot (ha!) topic the last couple of years.

 

[Markov Chaney]

@Neilski
I think it was this paper I read: https://arxiv.org/pdf/2402.12330

And here's another (which I haven't read yet, but notably it's an older paper from the same exoplanetary expert who has been in the news this week) https://arxiv.org/abs/2106.02061

ETA: The "news this week" has made it into Ars Technica and the first half of Dr Timmer's article is how you could have water but also there could be a bunch of other stable states, and it's full of links to more papers!

Skepticism greets claims of a possible biosignature on a distant world

It’s really difficult to get a clear sign of life on an exoplanet.

arstechnica.com

(Probably time we had an exoplanetary gossip thread in Off-Topic...)

 

[Neilski]

The question becomes how much atmosphere you need to stack under what gravity to hit that ~23 mbar pressure.

Yes, although I think you don't really need to care how much atmosphere (or gravity) is involved, since ED only reports the surface temperature and pressure (and Ian pointed out that below 10 mbar it'll say "no atmosphere"), and thus the equilibrium calculation is trivial to make at the surface. Since the radius and surface gravity are also mentioned, it wouldn't be terrifically difficult to work out the pressure vs altitude IFF you made the bold assumption that you knew the temperature vs altitude curve as well...

The only booboo seems to be you're talking like what you said makes it not possible at all, whereas actually you're relitigating what I said and calling out the assumptions needed to make it work.

Not sure what you mean here, but looking back, I may have misunderstood you to begin with. When you said "nope" in reply to me mentioning that something was broken (I was referring to the "water worlds that just don’t have an atmosphere to begin with" and I thought you were too), I thought you were saying that water worlds don't need to have an atmosphere - it's not clear now that you were saying that at all. Meanwhile, the 10 mbar threshold would explain the whole thing, since a cold surface (anything from a few degrees above freezing) would easily slip below the threshold.

I think it was this paper I read: https://arxiv.org/pdf/2402.12330

Ta! Which bit of that paper convinced you about which thing, though? Sorry, losing the thread here

 

[Reggit]

I'm pretty sure astronauts breathe low-pressure pure oxygen. I don't think it actually matters how much other inert gases there are as long as there's the right partial pressure of oxygen.

The problem isn’t overall atmospheric pressure, it’s oxygen “partial pressure”. If you’re breathing a one-fifth pressure atmosphere of pure O2, you’ll get about the same amount of oxygen as you will on Earth’s surface. Breathing a one-third pressure of Earth atmospheric mix of only 21% oxygen… different story.

Gotta keep a very close eye on that pressure when breathing pure oxygen!
Breathing pure oxygen, especially at normal atmospheric pressure, can be harmful and lead to oxygen toxicity, a condition where the lungs and potentially the brain are damaged.
Prolonged exposure can cause fluid buildup in the lungs (pulmonary edema) and shortness of breath.
In severe cases, it can lead to acute respiratory distress syndrome (ARDS) and death.

 

[Hank]

DAUM !!! We got some smart people on this forum. Just had to say it.
GL HF
... and have a great day

 

[Starsong]

Gotta keep a very close eye on that pressure when breathing pure oxygen!
Breathing pure oxygen, especially at normal atmospheric pressure, can be harmful and lead to oxygen toxicity, a condition where the lungs and potentially the brain are damaged.
Prolonged exposure can cause fluid buildup in the lungs (pulmonary edema) and shortness of breath.
In severe cases, it can lead to acute respiratory distress syndrome (ARDS) and death.

The minimum possible threshold for long-term oxygen toxicity is over 0.5 ATM pure o2- most of the oxygen craters in Elite are less than half that. The reason that 23.5% is given as a safety threshold is just because it’s a fire hazard, which I suspect Elite colonists could probably manage much better than we could with some 34th century gizmos/fireproof construction.
(https://bluefieldsafety.com/2023/12/safe-limits-for-oxygen-exposure-why-19-5-to-23-5/)