The Great Wall of Mars
Discussion
This came to my mind yesterday and I was wondering if the science behind it would stand up?
Premise: In a short story with the same title as the thread by Alastair Reynolds, he describes a microclimate created on Mars by the Conjoiner faction, in which a gigantic circular wall encloses a "breathable" and stable atmosphere on the surface of Mars, kind of like how the wall of a walled garden creates a Microclimate here on earth.
My question is; would such a thing work on Mars?
If the wall was tall enough could it hold a dense enough atmosphere in the low gravity of Mars (like liquid in a bowl)?
I assume the atmosphere would need to be topped up due to the stripping effect of the solar wind?
The idea has always fascinated me.
Premise: In a short story with the same title as the thread by Alastair Reynolds, he describes a microclimate created on Mars by the Conjoiner faction, in which a gigantic circular wall encloses a "breathable" and stable atmosphere on the surface of Mars, kind of like how the wall of a walled garden creates a Microclimate here on earth.
My question is; would such a thing work on Mars?
If the wall was tall enough could it hold a dense enough atmosphere in the low gravity of Mars (like liquid in a bowl)?
I assume the atmosphere would need to be topped up due to the stripping effect of the solar wind?
The idea has always fascinated me.
simon_harris said:
Good video and possibly a lot more plausible that building an massive wall. Simpo Two said:
Isn't the reason that Mars has very little atmosphere because most of it escaped into space? A wall isn't going to hold in stuff that goes upwards...
Some of the more nerdy Mars stans want to use sulphur hexafluoride to weigh down the atmosphere; combined with a less silly hole in the ground it might be slightly less impossible. 
hidetheelephants said:
Simpo Two said:
Isn't the reason that Mars has very little atmosphere because most of it escaped into space? A wall isn't going to hold in stuff that goes upwards...
Some of the more nerdy Mars stans want to use sulphur hexafluoride to weigh down the atmosphere; combined with a less silly hole in the ground it might be slightly less impossible. hidetheelephants said:
Simpo Two said:
Isn't the reason that Mars has very little atmosphere because most of it escaped into space? A wall isn't going to hold in stuff that goes upwards...
Some of the more nerdy Mars stans want to use sulphur hexafluoride to weigh down the atmosphere; combined with a less silly hole in the ground it might be slightly less impossible. In my head the wall would stop the atmospheres mixing, like if you had a bowl with dry ice in it? The idea would be to create a denser atmosphere which would sit in the bowl maybe?
Obviously the atmosphere would have to be topped up due to loss from mixing at the top of the wall and being stripped by the solar wind.
Edit; I just looked it up on a wiki page, the wall envisaged is 200km high, obviously not possible with todays tech.
Edited by 46and2 on Monday 4th December 10:39
Simpo Two said:
It makes about as much sense as making a coffee cup without a bottom, and then wondering how to keep the coffee in.
I propose you build a circular wall and put a roof on it to keep the atmosphere in. Have these wall fanatics not encountered roofs...?
Yea a roof might work.I propose you build a circular wall and put a roof on it to keep the atmosphere in. Have these wall fanatics not encountered roofs...?
In fairness the author of the short story I refer to is a genuine physicist who tries to make his stories "plausible" he must have put some thought into how this would work.
Gravity will hold the atmosphere down, so its not like a coffee cup with no bottom.
46and2 said:
In fairness the author of the short story I refer to is a genuine physicist who tries to make his stories "plausible" he must have put some thought into how this would work.
If he thinks a 200km high wall is plausible I wonder what his implausible ideas are?! 
What's needed to make this work with a wall of affordable height is my anti-gravity machine with an inverse mounting.
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