Thin atmosphere types and their rarities

[marx]

Time for a bit more research! I made a count of the various thin atmosphere types, their rarities, and also broke them down per body type. You can see the results at https://docs.google.com/spreadsheets/d/1eFev2Gh182FUporBzgrHGlls1rXVgrEirXbhhqXxrpI/.
Note that the various [gas]-rich atmospheres don't necessarily mean that said gas is the most abundant one in the atmosphere. When it comes to surface flora, these bodies tend to have significantly fewer of those anyway.

Some highlights from the results then:

• Thin Neon atmospheres are the most common in the galaxy, thanks to icy bodies being so numerous. Thin Argon comes in at third because of this too.
• Thin Ammonia-rich atmospheres are the most rare landables in the galaxy, with only 10 currently known. This could be because their atmosphere compositions are, shall we say, quite varied.
• This is widely known, but just to make sure: out of the "pure" atmosphere types, Thin Water atmospheres are the most rare in total, followed somewhat closely by Thin Oxygen.
• Almost all of the "pure" atmosphere types are present on any body combination, with the exception of Metal-Rich + Ammonia or Nitrogen. Of course, there are still ones that are very rare.
• Hot thin Metallic Vapour atmospheres would be the second most rare overall: however, none of them are landable. They're all on Metal-Rich bodies, so it's likely that the developers deliberately made this atmosphere type non-landable. (It'd make sense anyway.)
• Hot thin Silicate Vapour atmospheres make up almost 99% of the thin atmospheres found on Metal-Rich bodies, but only 0.2% of them are landable. The probable reason for this is that the non-landables might have lava on their surfaces. (Unfortunately, we can't tell that just from journal data.)
• There is one atmosphere type that's below 0.1 atm and present in the game, but not on any landable body types: "Thin Ammonia and Oxygen", found only on Ammonia Worlds.

Also, the three most common atmosphere types per body type:

High Metal Content bodies: Thin Sulphur Dioxide (42%), Thin Carbon Dioxide (33%), Thin Ammonia (8%)
Icy bodies: Thin Neon (48%), Thin Argon (25%), Thin Neon-rich (13%)
Metal-Rich bodies: Hot thin Silicate Vapour (99%, but only 0.2% of them are landable!), Thin Sulphur Dioxide (0.5%), Hot thin Sulphur Dioxide (0.49%)
Rocky bodies: Thin Carbon Dioxide (63%), Thin Ammonia (22%), Thin Sulphur Dioxide (11%)
Rocky Ice bodies: Thin Argon (47%), Thin Neon (24%), Thin Neon-rich (13%)

The least common types can be fairly close together in counts, so over time, they might even fluctuate.

As always, thanks for reading!

 

[Alkibiades]

Did you look into the paramters for certain temperature or gravity limits for each atm type?

 

[marx]

Nope, I didn't. They'd probably be fairly evident (at the very least, temperatures would), but hey, that's something to take a look at too.

 

[Alkibiades]

Yes indeed. Due to that one non landable planet that caused a headache in the igau discord I figured that there is probably a G limit for thin nitrogen atm and I am going to visit the two haviest planets in the galaxy that have thin n2 atm to have the actual data in the logs.

System names:
Wepue EI-W c17-4613
Flyumboo UN-X c3-0

 

[marx]

Alright, so the results of a quick look at the thin Nitrogen atmospheres: seems fairly obvious that there was a bug either with the game, or with data uploading (the journals?). Several thousand thin Nitrogen planets were wrongly classified as that (most of them uploaded between 2017. March 27 and 30, which didn't have any updates released then), as their surface pressures were far in excess of what thin ought to be. Remove those entries, and the ranges for surface gravity and temperature become much more believable.

I'm not sure about those two system names though: I can't seem to find Wepue EL-W c17-4613 in any database, and Flyumboo UN-X c3-0 1 is logged with a surface gravity of ~0.8 g, which wouldn't be the heaviest of thin Nitrogen landables. That record appears to belong to IC 1396 Sector UU-O d6-8 6, and 1.2 g surface gravity seems to be a hard limit for landables in this category. (Whereas the non-landables go up to ~1.55 g.)

Not surprisingly, the highest gravity landables look to all be thin Helium atmospheres, with the exception of some named planets in the bubble, with Darahk V [sic] standing well above the rest, with a thin Carbon Dioxide atmosphere. Named bubble bodies shouldn't count though.

 

[Alkibiades]

The planet that caused a headache was a high metal content planet. Yes there are others that have a higher gravity but not any kind of hmc, which I limited my search to.

Lets try again with the system names:

Wepue EI-W c17-4613
Flyumboo UN-X c3-0

 

[marx]

Ah, you didn't say that you were looking at HMCs only. In that case, yeah, it certainly looks like there are some hard gravity limits for landability then, with breaking stuff down by atmosphere and body type too. Might be interesting to go look in person at the ones that aren't landable, see what the differences might be.

 

[marx]

@Alkibiades : okay, I've checked the outliers in the bubble, and I'm reasonably certain that the reason the developers put in some hard limits for thin atmo gravity and body types is because the surface generation doesn't handle too high gravity well. Especially when it comes to settlements, because while one might explain away too "rugged" terrain, it'd be difficult to explain why a settlement's buildings and roads are well above the ground. Also, I don't know why Cet 5 had those small dust clouds appear on the surface much more frequently than they usually do - how would gravity increase that?

So yeah, a surface gravity of 2 g on a thin atmo icy body still works well with this surface generation, but on a high metal content planet, it doesn't.
It's actually quite fortunate that the developers forgot about the few manually edited outliers that are in the bubble and left them landable.

Thanks for bringing this topic up! It was interesting to look into.