"The mountains reared grandly around. Most were whitecapped; glaciers shimmered blue-green under the shrunken sun. Pioneers had melted the snow off Mt Horn and emplaced thermonuclear fires underground to keep rock and air liveably warm. Now the ice bulls and the frost-loving plants they had grazed were gone. Woods fringed the city. Agriculture occupied lower reaches, as far down as sea level. But humans dared not breathe there, unless through a reduction helmet. At those pressures, the gases their lungs required became poisons."
-Poul Anderson,
Flandry's Legacy (New York, 2012), p. 236.
Usually, I try to paraphrase Anderson's descriptions but sometimes a paragraph is compact enough to be quoted in full. In less carefully written science fiction, a planetary atmosphere would be either breathable or not. However, on Starkad, the atmosphere was as described in this passage about Imhotep so the Starkadian Tigeries were settled in the Imhotepan lowlands. They must wear air helmets or oxygills to visit the human-occupied highlands.
3 comments:
Hi, Paul!
And, as I argued in a previous note, altho not shown or directly stated, humans too probably used the reverse kind of oxygills in order to breathe the otherwise poisonous atmosphere of the lowlands. Because that would be more convenient for those humans whose business, official or private, took them among the Tigeries for stays longer than a standard day or so.
Sean
"a planetary atmosphere would be either breathable or not"
Earth's atmosphere is fine at 100 kPa. 2 or 3 times that is still OK but don't decrease the pressure to 100 kPa fast or you get the bends.
Increase the pressure to 600 or more kPa & almost everyone gets nitrogen narcosis. The increased oxygen partial pressure can also cause problems at modest depths while scuba diving.
Kaor, Jim!
And we see that in Anderson's stories set on Rustum, in ORBIT UNLIMITED and NEW AMERICA.
Ad astra! Sean
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