/sci/ - Science & Math

Continuing from last thread, what would a "terraformed" Hellas Basin look like?
Atmosphere just over the Armstrong limit, requiring breathing masks because it's poison. A small ocean/large brine lake that probably too toxic for humans to use it as anything but thermal mass. Weird genetically-edited lichen and microbial mats everywhere, conditioning the soil and water.
For colonists, it would be paradise- they could walk around outside in regular clothes.

So- partial terraforming.
Could you "fill" Hellas Basin with an atmosphere that would let humans walk around without pressure suits, sort of like a brine pool on the ocean floor, or do gases not like to behave that way?

Could Hellas retain a livable atmospheric pressure?