Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > Roleplaying in General

Reply
 
Thread Tools Display Modes
Old 01-22-2020, 10:40 PM   #21
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: Sci-Fi World-building: Mars the farm planet?

Quote:
Originally Posted by AlexanderHowl View Post
Your main issues are nitrogen and water. Everything living requires nitrogen, and Mars practically has no nitrogen and very little water. In order to create 1 atmospheric pressure, you would require the equivalent of two Earth atmospheres worth of nitrogen (around 10 quadrillion metric tons). The nearest sources of massive quantities of free nitrogen are Earth (~0.8 atmospheric masses), Venus (~4 atmospheric masses), Titan (~4 atmospheric masses).

As for water, you would need a minimum of 10 quadrillion tons of water to make Mars as habitable as the Atacama Desert, and a minimum of 100 quadrillion tons of water to attempt any massive agriculture for local support. Anything less, and the atmosphere will just suck up the water.

So, we are talking about a minimum of 110 quadrillion metric tons of nitrogen and water. Now, you can produce oxygen locally, so you could reduce that to around 21 quadrillion metric tons, but you would need a way to transport the hydrogen (ammonia would be a partial solution, but 10 quadrillion tons of hydrogen can only transport ~2 quadrillion tons of hydrogen).

But wait, there is more. Every kilogram of matter traveling from LMO to Mars surface possesses ~10 MJ of energy, meaning that 21 quadrillion metric tons generates 210 YJ of energy. Mars only receives around 25 PJ/s, so the energy from transporting the necessary materials to Mars would be equal to 8.4 billion seconds of sunlight, around 250 Earth-years. To avoid boiling off everything, you would probably need to spend 1000 Earth-years just dropping stuff onto Mars.
I think some of your math might be wrong. According to this NASA fact sheet, the current mass of Mars' atmosphere is only 25 trillion metric tons. I might be wrong about this, but I thought the relationship between atmosphere mass and atmospheric pressure was linear?
Michael Thayne is offline   Reply With Quote
Old 01-22-2020, 11:00 PM   #22
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: Sci-Fi World-building: Mars the farm planet?

Also, could some plants—perhaps genetically engineered ones—survive in a mostly-CO2 atmosphere derived from melting Mars' (dry) ice caps?
Michael Thayne is offline   Reply With Quote
Old 01-23-2020, 12:07 AM   #23
Bengt
 
Bengt's Avatar
 
Join Date: Oct 2005
Location: Ronneby, Sweden
Default Re: Sci-Fi World-building: Mars the farm planet?

Quote:
Originally Posted by Michael Thayne View Post
Also, could some plants—perhaps genetically engineered ones—survive in a mostly-CO2 atmosphere derived from melting Mars' (dry) ice caps?
GEd single cell organisms is more plausible. We already have some living in pretty weird places to work with.
Bengt is offline   Reply With Quote
Old 01-23-2020, 07:41 AM   #24
ericthered
Hero of Democracy
 
ericthered's Avatar
 
Join Date: Mar 2012
Location: far from the ocean
Default Re: Sci-Fi World-building: Mars the farm planet?

Quote:
Originally Posted by AlexanderHowl View Post
Your main issues are nitrogen and water.
On the amount of nitrogen, you "only" need about 60% of an earth atmosphere. You've got to stack twice and a half as much on any given spot, but mars has about a quarter of the surface area as earth.

But that's not a farming problem, that's a terraforming problem, and some neo-emperor or the other already spent the stupid amount of money to get you there. You've on a planet mostly terraformed but with too much CO2 where mars is, how do you profit off the former crazy whale's extravagance?
__________________
Be helpful, not pedantic

Worlds Beyond Earth -- my blog

Check out the PbP forum! If you don't see a game you'd like, ask me about making one!
ericthered is online now   Reply With Quote
Old 01-24-2020, 12:52 AM   #25
Bengt
 
Bengt's Avatar
 
Join Date: Oct 2005
Location: Ronneby, Sweden
Default Re: Sci-Fi World-building: Mars the farm planet?

If you have liquid surface water in a mostly CO2 atmosphere it will have significantly lower pH than on earth as the CO2 dissolves and form carbonic acid. Don't know what pH will be when the oceans are saturated as what I've read is about earth with 0.04% CO2.
Bengt is offline   Reply With Quote
Old 01-24-2020, 04:30 AM   #26
Anders
 
Anders's Avatar
 
Join Date: Jan 2005
Location: Gothenburg, Sweden
Default Re: Sci-Fi World-building: Mars the farm planet?

It depends on the partial pressure of CO2 and the temperature.

There's a table here:

https://en.wikipedia.org/wiki/Carbonic_acid

But genetic engineering can probably overcome the pH problem.
__________________
“When you arise in the morning think of what a privilege it is to be alive, to think, to enjoy, to love ...” Marcus Aurelius
Anders is offline   Reply With Quote
Old 01-24-2020, 10:35 AM   #27
Daigoro
 
Daigoro's Avatar
 
Join Date: Dec 2006
Location: Meifumado
Default Re: Sci-Fi World-building: Mars the farm planet?

Quote:
Originally Posted by Agemegos View Post
Still, you have to reckon that it will take on the order of centuries to create topsoil.
I'm not sure it needs that long. Volcanic lava flows can become vegetated in a matter of years or decades. They do have the advantage of having biotic material carried in from neighbouring regions, but they still develop a sustaining soil fairly quickly.

Source: My visit to Sakurajima volcano, and a tourist sign showing a diagram of revegetation. 30 years for grasses to colonise bare rock, 80 years for low shrubs, 100 years for tall trees, 200+ years for so-called "climax forest" (mature, steady state growth).
__________________
Collaborative Settings:
Cyberpunk: Duopoly Nation
Space Opera: Behind the King's Eclipse
And heaps of forum collabs, 30+ and counting!

Last edited by Daigoro; 01-24-2020 at 10:54 AM.
Daigoro is offline   Reply With Quote
Old 01-24-2020, 02:17 PM   #28
Agemegos
 
Agemegos's Avatar
 
Join Date: May 2005
Location: Oz
Default Re: Sci-Fi World-building: Mars the farm planet?

Quote:
Originally Posted by Daigoro View Post
I'm not sure it needs that long. Volcanic lava flows can become vegetated in a matter of years or decades. They do have the advantage of having biotic material carried in from neighbouring regions, but they still develop a sustaining soil fairly quickly.

Source: My visit to Sakurajima volcano, and a tourist sign showing a diagram of revegetation. 30 years for grasses to colonise bare rock, 80 years for low shrubs, 100 years for tall trees, 200+ years for so-called "climax forest" (mature, steady state growth).
Around here a lot of spotted-gum forest grows on poor shale country where there isn't enough topsoil to grow crops. (Where the soil is eighteen metres deep the land has been cleared for farming.) Trees will grow to considerable heights in ground you couldn't possibly draw a plough through or pick a potato from if one grew, and put down deep roots in freely-draining material that won't retain moisture in the root zone of grasses and herbaceous crops.

You can grow plants in sand or vermiculite if you pour on enough water and fertilisers, but you have to keep them out of the rain. That's essentially hydroponics, not agriculture.

Of course futuristic designer crops could well be deep-rooted perennials that you run a header over but don't plough in and re-plant over.
__________________

Decay is inherent in all composite things.
Nod head. Get treat.

Last edited by Agemegos; 01-24-2020 at 02:43 PM.
Agemegos is offline   Reply With Quote
Old 01-26-2020, 05:13 PM   #29
Michael Thayne
 
Michael Thayne's Avatar
 
Join Date: May 2010
Default Re: Sci-Fi World-building: Mars the farm planet?

Quote:
Originally Posted by AlexanderHowl View Post
As for water, you would need a minimum of 10 quadrillion tons of water to make Mars as habitable as the Atacama Desert, and a minimum of 100 quadrillion tons of water to attempt any massive agriculture for local support. Anything less, and the atmosphere will just suck up the water.
Thinking about this more, I wonder if it's more complicated than that. Sure you might need 100 quadrillion tons to get significant ocean coverage on Mars, but less isn't going to produce a uniform desert—I suspect 10s or 100s of trillions of tons of water would be enough for small seas / lakes here and there? Might be wrong about the dynamics of it tough.
Michael Thayne is offline   Reply With Quote
Old 02-12-2020, 08:57 AM   #30
hcobb
 
hcobb's Avatar
 
Join Date: Aug 2004
Location: Pacheco, California
Default Re: Sci-Fi World-building: Mars the farm planet?

The why is simple. Somebody nukes Morocco and Earth no longer grows food.

https://en.wikipedia.org/wiki/Peak_phosphorus
__________________
-HJC
hcobb is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 07:35 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.