DISCLAIMER: This edge case doesn't appear to have been anticipated by Frontier, and as such isn't currently represented in the game mechanics. Therefore, this is all (for now) roleplay/immersion only.
As many of you probably thought upon the announcement of landable atmospherics, one of the major questions was - can we breathe on any of them? Unfortunately, with the highest atmospheric pressure we can land on being a mere 10% of Earth's, that seems unlikely. Even with a pure-oxygen atmosphere at the 10% threshold, breathing it would require an experienced mountain climber who was already acclimatised to the lowest pressure a human can be. Not much chance for the rest of us, then.
But. Whilst we're on the topic of mountains... if you can turn the breathable atmosphere of Earth into an unbreathable one by climbing to the top of Mount Everest, can you turn an unbreathable atmosphere into a breathable one by going down?
After a lot of surveying and calculations, it turns out the answer is... yes.
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!
All the maths, for anyone who wants to read it (or check my calculations)
As many of you probably thought upon the announcement of landable atmospherics, one of the major questions was - can we breathe on any of them? Unfortunately, with the highest atmospheric pressure we can land on being a mere 10% of Earth's, that seems unlikely. Even with a pure-oxygen atmosphere at the 10% threshold, breathing it would require an experienced mountain climber who was already acclimatised to the lowest pressure a human can be. Not much chance for the rest of us, then.
But. Whilst we're on the topic of mountains... if you can turn the breathable atmosphere of Earth into an unbreathable one by climbing to the top of Mount Everest, can you turn an unbreathable atmosphere into a breathable one by going down?
After a lot of surveying and calculations, it turns out the answer is... yes.
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!
All the maths, for anyone who wants to read it (or check my calculations)
First, we have to work out something called the scale height. This is the distance over which the pressure changes by the factor of e (2.718). According to Wikipedia, this is calculated by (Hc * T)/(m*g), where:
Hc = The Hoffman constant, or 1.381 x 10^-23. A very small number.
T = Average atmospheric temperature (in kelvins). More on this below.
m = Mass of each atmospheric molecule, so 5.314x10^-23 for oxygen.
g = Gravity in metres per second. For Swoilz's 0.48G, this is 4.7088.
Calculating the temperature is a bit complicated. The average given for Earth is 250K, but Swoilz is much colder than Earth in general (235K average temperature vs Earth's 288K) so we can assume it's lower than this. As a guesstimate, I've decided to take the difference in Earth (38K) and divide that by the difference between Earth and Swoilz's temps, then take that away from Swoilz's average surface temp. If that makes any sense. So 38 * (235/288) = 31, and 235 - 31 = 204.
So, the scale height is (1.381x10^-23 * 204)/(5.314x10^-23 * 4.7088) = 11.2588km. Finally, a useful number!
Then, we need to work out the actual pressure at 8.5Km down. Since the scale is exponential, the calculation should be Swoilz's base atmospheric pressure of 0.09727 times e^(8.5/11.2588), which equals 0.20695, or 20.695%. Probably better to round this to just 20.7% as there will be some inaccuracies in my measurements.
All stats on Swoilz's parameters come from Spansh's page on the planet.
Hc = The Hoffman constant, or 1.381 x 10^-23. A very small number.
T = Average atmospheric temperature (in kelvins). More on this below.
m = Mass of each atmospheric molecule, so 5.314x10^-23 for oxygen.
g = Gravity in metres per second. For Swoilz's 0.48G, this is 4.7088.
Calculating the temperature is a bit complicated. The average given for Earth is 250K, but Swoilz is much colder than Earth in general (235K average temperature vs Earth's 288K) so we can assume it's lower than this. As a guesstimate, I've decided to take the difference in Earth (38K) and divide that by the difference between Earth and Swoilz's temps, then take that away from Swoilz's average surface temp. If that makes any sense. So 38 * (235/288) = 31, and 235 - 31 = 204.
So, the scale height is (1.381x10^-23 * 204)/(5.314x10^-23 * 4.7088) = 11.2588km. Finally, a useful number!
Then, we need to work out the actual pressure at 8.5Km down. Since the scale is exponential, the calculation should be Swoilz's base atmospheric pressure of 0.09727 times e^(8.5/11.2588), which equals 0.20695, or 20.695%. Probably better to round this to just 20.7% as there will be some inaccuracies in my measurements.
All stats on Swoilz's parameters come from Spansh's page on the planet.