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 intrusted 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. ______________________________________________________________