Mars: A Future Home for Humanity chapter four

         THE GREENING OF MARS
                                       (c) Robert Zubrin & Chris McKay

         "To see it in our power to make a World happy...to exhibit on
         the theatre of the Universe a character hitherto unknown- and
         to  have,  as it were, a new creation entrusted to our hands,
         are honours that command reflection and can  neither  be  too
         highly   estimated   nor  to  gratefully  received"  -  Thomas
         Paine,1783

         The first steps toward the  transformation  of  Mars  into  a
         habitable  planet  will begin with the establishment of large
         scale   settlements.  These  outposts  will  allow  continued
         in  depth  field  exploration  to  determine   the   planet's
         potential  resources, and engineering research to develop and
         prove  appropriate  techniques for using increasing arrays of
         Martian resources to support the needs of human settlements.

         Initial Mars Direct exploration missions approach Mars  in  a
         manner akin to terrestrial hunter-gathers, utilizing only the
         most  readily available resource, the atmosphere, to meet the
         basic needs of fuel and oxygen. In  contrast,  a  permanently
         staffed  base  will  approach  Mars  from  the  standpoint of
         agricultural and industrial  society;  developing  techniques
         for  extracting  water  out  of  soil; conducting large scale
         greenhouse agriculture; making ceramics, metals, glasses  and
         plastics   out   of   local   material;   constructing  large
         pressurised structures for living and working; and supporting
         increasingly sophisticated field investigations.

         The  possibility  of  creating  a   new   branch   of   human
         civilization  on  Mars  depends primarily upon the ability of
         the Mars base  (or  bases)  to  develop  local  resources  to
         support   a   significant   population.   While  advances  to
         propulsion are certainly welcome, highly cost effective,  and
         definitively  worth  pursuing,  limited  space transportation
         technology  is  not  the  primary  obstacle  to   the   human
         settlement of Mars.  An immigration rate of 100 people a year
         (achievable  with either chemical propulsion and aerocapture,
         or 1960's vintage nuclear thermal technology) would result in
         a rate of population growth comparable to that experienced in
         colonial America in the 1600s and 1700s.

         No,  the  problem of settling Mars is not one of transporting
         people across space - its supporting them once they are there
         Once again, the ability to master the local  environment  and
         use its resources is the key, and the ultimate mastery of the
         Martian environment lays in "terraforming".

         Many  people  can  accept  the  possibility  of a permanently
         staffed  base  on  Mars,  or  even  establishment  of   large
         settlements.  However,  the  prospect of drastically changing
         the planets temperature and  atmosphere  towards  more  Earth
         like conditions, or "terraforming" seems to most people to be
         either  sheer  fantasy  or at best, a technological challenge
         for the far distant future.

         But is this pessimistic point of view  correct?  despite  the
         fact  that  Mars  today  is  cold,  dry and probably lifeless
         planet, it has all the elements  required  to  support  life:
         water,  carbon  and oxygen (as carbon dioxide), and nitrogen.
         The physical aspects of Mars, its gravity, rotation rate  and
         axial  tilt  are  close  enough  to  those  of  Earth  to  be
         acceptable and it is not too far from  the  sun  to  be  made
         habitable.

         Studies  utilizing  climate  models  suggest that it could be
         possible  to  make  Mars  habitable  again  with  foreseeable
         technology.   As  a first step, Mars' tenuous atmosphere must
         be thickened up somehow. Pumping more gas into the atmosphere
         could accomplish this, but that begs  the  obvious  question:
         where do you get the gas from? The answer, again, is that you
         don't  -  Mars already harbors it. We are fairly certain that
         there are large reserves of  carbon  dioxide  frozen  in  the
         south  polar  cap  and  locked  up  within  the soil - enough
         reserves, in fact, to  increase  Mars;  atmospheric  pressure
         from its current 1 percent to nearly 30 percent.

         The  key  to unlocking the trapped CO2 is to heat the planet.
         In fact, the warming and cooling of  Mars  that  occurs  each
         Martian  year  as  the  planet cycles between its nearest and
         furthest positions from the Sun in  its  slightly  elliptical
         orbit causes the atmospheric pressure on Mars to vary plus or
         minus 20 percent to its average value on a seasonal basis.

         Heating Mars is the right thing to do for another reason: the
         planet  is much too cold. Raising the temperature of at least
         the equartorial regions to around 0 deg C - the melting point
         of water ice- would be ideal. But, that would translate  into
         a   rise   of  about  55  deg  C  from  the  planets  present
         temperatures- a fairly major trick. After all, its not as  we
         could move Mars to a warmer orbit.

         However we do know of one way to heat a planet - in fact,  we
         are already inadvertently (and probably unadvisedly) doing it
         on  Earth.   We  are,  many  believe,  heating our own planet
         through an  artificially  induced  "greenhouse"  effect  that
         traps  the  Sun's  heat within our atmosphere. The greenhouse
         gases that may be leading Earth down a deadly path  -  carbon
         dioxide  and  cholorflorocarbons  ( CFCs) - could potentially
         drive Mars along a road that would lead to  a  living,  green
         planet.

         All the necessary elements for producing CFCs can be found on
         Mars. Establishing factories on Mars to produce CFCs and dump
         them  into  the  Martian  atmosphere  would  warm  the planet
         sufficiently to release large amounts of carbon dioxide  from
         the  polar  cap and soil. This newly liberated, CO2 would, in
         turn, further  warm  the  atmosphere  which,  in  turn  would
         release   more   CO2   from   the   regolith.    In  essence,
         jump-starting the warming of the Martian atmosphere leads  to
         a  positive  feedback system- the warmer it gets, the thicker
         the  atmosphere  becomes,  and  the  thicker  the  atmosphere
         becomes, the warmer it gets.

         Still,  to  warm  the  planet 55 deg C sounds like an arduous
         task.  But, recall articles you may have read  about  Earth's
         own   global  warming,  and  dire  warnings  of  a  "runaway"
         greenhouse effect, such as the one believed  to  have  turned
         Venus  into  the  planetary  furnace  it  now  is.  The vapor
         pressure and temperature of the Martian  atmosphere  co-exist
         in  a delicate balance.  Upsetting that balance can cause the
         atmosphere to careen toward a new equilibrium  point,  but  a
         point which is far removed from the equilibrium we find today
         on Mars. Its akin to removing a stone at the bottom of a pile
         of  rocks  several meters high. The pile collapses; stone and
         rock tumbling down its slopes  until  a  new  equilibrium  is
         reached.

         Our calculations reveal that a minor change in temperature at
         the  Martian  South pole - just 4deg C- can kick-in a runaway
         greenhouse affect in the polar region that will result in the
         evaporation of the polar cap and the liberation of  the  vast
         qualities of carbon dioxide locked in the Martian soil.  This
         induced  4deg C warming will essentially "flip the switch" on
         the Martian greenhouse and will in a  relatively  short  time
         period, result in an atmosphere that is thick enough and warm
         enough to allow the waters of Mars to flow once again.

         Once  significant  regions  of  Mars  rise above the freezing
         point of water on  at  least  a  seasonal  basis,  the  large
         amounts of water frozen in the soil as permafrost would begin
         to  melt, and flow out into the dry river beds of Mars. Water
         vapor is a  very  effective  greenhouse  gas,  and  thus  the
         reappearance of liquid water on the Martian surface would add
         to   the   avalanche   of   self-accelerating   effects   all
         contributing to the rapid  warming  of  Mars.   The  seasonal
         availability  of  liquid  water  is  also  the  key factor in
         allowing the  establishment  of  natural  ecosystems  on  the
         surface of Mars.

         The  dynamics  of  the  regolith gas-release process are only
         approximately understood, and the total available reserves of
         carbon dioxide won't be known until human explores journey to
         Mars to make a detailed assessment, so our results  are  only
         approximate.   Nevertheless,  it  is  clear that the positive
         feedback generated  by  the  Martian  CO2  greenhouse  system
         greatly  reduces  the engineering effort that would otherwise
         be required to transform the Red Planet. In fact, the  amount
         of  greenhouse  gas  required  to  heat  a  planet is roughly
         proportional to the square of the desired temperature change.
         Driving Mars into a runaway  greenhouse  with  an  artificial
         4deg  C  temperature rise, therefore, only requires 1/200 the
         effort that would be needed if the entire 55 deg C  rise  had
         to  be engineered by brute force. In fact, the power required
         to produce the CFCs necessary to drive a  4  deg  C  rise  in
         temperature  is in order of that produced by a single, modern
         nuclear power plant.

         In a matter of several decades,  Mars  could  be  transformed
         from  its  current  dry and frozen state into a moist and wet
         planet capable of supporting life.  Humans could  not  breath
         the  air  of  this transformed life, but they would no longer
         require space suits. Instead they could travel freely in  the
         open   wearing   ordinary  clothing  and  simple,  scuba-type
         breathing gear. And because the outside atmospheric  pressure
         will  have  been  raised  to  tolerable  levels,  it  will be
         possible to have  large  habitable  areas  for  humans  under
         dome-like inflatable tents containing breathable air.

         Plants  could  thrive  in  the  carbon  dioxide-rich  outside
         environment, and spread rapidly across the planet's  surface.
         In  the  course  of  centuries,  these plants would introduce
         oxygen  in  Mars'  atmosphere  in   increasingly   breathable
         qualities. Eventually the day would come when the domed tents
         would  be opened to the breath of life carried in the Martian
         winds.

         Such is the potential future indicated by current theory. But
         only human explorers operating on Mars can learn enough about
         the planets and the methods of  utilizing  its  resources  to
         transform  such  a  dream  into  reality.   Yet  the  game is
         certainly worth the candle, for what is at stake is an entire
         world. Mars could become, once again, a second home for life,
         all life - not only humans, not only just for " the  fish  of
         the  sea...the  fowl  of the air, and every living thing that
         moveth upon the Earth," but for a plenitude  of  species  yet
         unborn.  New  worlds  invite  new  forms,  and  in  the novel
         habitats that a terraformed Mars would provide, life  brought
         from  Earth  could  go  forth  and  multiply  into  realms of
         diversity yet unknown.

         This is  the  wondrous  heritage  we  can  leave  for  future
         generations - not only a new world for life and civilization,
         but  an example of what men and women of intelligence, daring
         and vision can accomplish  when  acting  upon  their  highest
         ideals. No one will be able to look upon the new Mars without
         feeling  prouder to be human. No one will be able to hear its
         story without being inspired to rise to the tasks  that  will
         lie ahead among the stars.

         ==============================================================

                     GREENHOUSING MARS WITH CFCS

   Induced  heating    CFC  Pressure       CFC  Production     Power Required
     (degrees C)        (millibars)         (tonnes/hour)          (MWE)

     5                  0.000012                263              1.315
     10                 0.00004                 878              4,490
     20                 0.00011                 2,414            12,070
     40                 0.00022                 4,829            24,145
     60                 0.0008                  17,569           87,845

         This table shows the amount of CFC needed in Mars  atmosphere
         to  create a given temperature rise, and the power that would
         be needed on the Martian surface to produce the required CFCs
         over a period of 20 years. If the gasses have an  atmospheric
         lifetime of a hundred years. then approximately one-fifth the
         power  levels  shown  in the table will be needed to maintain
         the CFC concentration after it has been build up. Note that a
         5 deg temperature rise  -  enough  to  kick  in  the  runaway
         greenhouse  affect-  requires  slightly  more then 1000MWe of
         power, about the output of a typical nuclear power plant used
         on Earth today.  It is unlikely that mounting  an  industrial
         effort  of this scale on Mars will be beyond the capabilities
         of the early 21st Century.

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