Re: (TFT) Mars - Plants get too hot on Luna.

[Rick Smith <rsmith@lightspeed.ca>]

Hi Dan,
  The main problem with artificial light is it is so
expensive.  One square km of plants needs the power
to run a large city.  The plants on the farms of 
Rhode Island (that agricultural giant) would require
more power than the civilization of the whole Earth.

  That is the main problem of growing crops on Luna.
Its 28 day long day means that the plants roast and
freeze.  (Apart from the fact that all the volatiles 
that plants need except oxygen are missing from the
moon.)  Mars is the one place in the solar system 
apart from Earth where plants can grow using natural
sunlight.

  Plants can take 1/3 as much light as Earth gets and
still do OK.  This means that plants that don't need
strong sunlight can do well on Mars.  Beyond Mars it
gets very hard to grow plants with only natural sun
light.  (But on the asteroids you could use natural
sunlight and a quite modest amount of artificial 
light to help.  Rotate your asteroid so it has about
a 24 hour day tho.)

  Artificial light (which has the correct wave lengths)
can grow plants.  However, getting a broad spectrum 
light is a more expensive than the cheaper lights.

  Mars' atmosphere is enough to screen out all 
normal solar radiation and most of the solar radiation
from a solar storm.  (People should go into storm 
shelters for a few hours during the coronal mass
ejection.)  The cosmic ray dose is less than half of
deep space.  (The ground stops half, and the thin
atmosphere actually helps a bit.  Remember that the
scale height is 3 times Earth so even tho the pressure
is 1/100 Earth's, it protects as if the pressure was
3/100th's Earth's.)  This is fine for explorers.  If
you were going to live all your life on Mars, you 
would want a habitat that had a meter of dirt over
you.  But being completely underground is not needed.
You can have windows.

If you were going to have mines on the Asteroid belt,
you would likely end up with a triangle trade:

-- High tech, low mass materials from Earth to Mars.
-- Low tech food and crafts (clothes, plastics, wire,
metals, ceramics, etc.) from Mars to the Asteroids.
-- High value metals, gold, platinum, rhodium, palladium,
etc. go from the Asteroids to Earth.

It is at least 50 times cheaper to go from Mars surface
to Ceres as it is to go from Earth's surface to Ceres,
so anything that can be built on Mars would be.  Only
the highest, most complex items would be shipped from
Earth.

Warm regards, Rick. 


On Tue, 2011-09-08 at 18:54 -0400, dwtulloh61@cox.net wrote:
> Hey Rick,
> 
> Assuming subsurface water exists in sufficient quantity to support life, do
> you think it would ever be possible for humans to live underground in some
> sort of self-sufficient capacity there?
> 
> Everything I've read suggests that plants do not grow well in artificial light
> which, if true, presents a serious problem to developing a self-sustaining
> in space.
> 
> Dan
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