QUESTION:
I am researching hydroponics possibilities (including energy requirements)
on Mars and have a few questions. First, how would I emulate roughly the
amount of sunlight which would fall on Mars on average (what kind of filter
if any)? My hydrponics unit will be small (1ft*1ft*4inch) and will probably
use a 150watt High-pressure sodium lamp. Second, does the martian soild
contain enough hydrogen to produce water (with oxygen brought over from
earth)? On the poles? Finally, what is the current payload cost of chemical
rockets? Thank you very much for your time.

ANSWER from Jeff Plescia on March 10, 2000:
The solar constant at Mars is about 589 W / sq m, about
43% of the value for the Earth (1368 W sq m).  So all you
need to do is turn down the light.  For the purposes of
your experiment the spectral absorption differences between
a CO2 atmosphere (Mars) and an N2 atmosphere (Earth)
are probably not important.

There is no free Hydrogen in the soil.  Typically the
idea is to bring the Hydrogen from Earth, since it
is low mass, and combine it with martian oxygen.
The oxygen could be obtained from spliting the
CO2 atmophere molecules or from the soil.  One
could also get water directly form the martian
atmosphere by freezing it out.  There is water in
the atmosphere, but not much.  You would need
to cycle a lot of air, but that's probably cheaper
than a pipe from the polar caps.