by Andreas Steffen
For decades, the possibility of landing humans on Mars, and rendering it habitable for us has fascinated minds everywhere, from Sci-Fi writers to NASA specialists. Great scientific attention has been paid to this opportunity, for the gain would incredible: A world with a similar land mass as Earth, available for exploitation and colonization. Indeed an enticing prospect, and one whose net value has been estimated by some at $200,000,000,000,000 US, or 200 trillion dollars (Robinson: Green Mars). But the obstacles are just as formidable as the gains. This paper will attempt to detail the obstacles facing the terraforming of this new world, irrespective of the problem of interplanetary transport. Which is not to say that these are not equally hampering.
CURRENT STATUS OF MARS
Fact is that no human has so far set foot on the surface of the red planet. What information we have is from several fly-by probes, as well as observations through telescopes. Recently, however, the remote controlled lander PATHFINDER touched down on Mars' regolith and began analyzing rock samples, etc. All these methods of gathering information have revealed quite a bit about Mars. The planet appears to consist mostly of dead rock, with tectonic activity at a minimum. A prevalence of ferric oxide makes for the familiar red color. The atmosphere is extremely thin, and lacking in both oxygen and nitrogen, making for high levels of cosmic radiation on the surface, as well as an extremely weak greenhouse effect. Most of the insulation is rebounded into space, which contributes to the low temperature, about 220¼K on average. This ensures that there is no active hydrosphere, since all water is frozen up and therefore not available for chemical interact ion. The probes have also failed to detect any kind of biosphere, although it might have escaped their sensors.
As a source of atmospheric material, the two polar caps are considered a good reservoir. Recent research, however, has concluded that they are not, as so far thought, carbon dioxide, but rather water ice with amounts of other materials bound into it. Melting them will therefore fail to increase the carbondioxide content of the atmosphere as much as was assumed. Yet the amount present will suffice for an atmosphere of 300 mbar (earth has 1000+ mbar at sealevel) Also, the regolith seems to carry significant amount of this gas. While liberating it from there will be more of a challenge than melting the polar caps, this is an even bigger supply of it on Mars.
THE TWO PHASE MODEL (hereafter referred to as TPM)
The idea behind this is to divide the terraforming process into 2 stages: In the first, the atmosphere is thickened and warmed with massive CO2 influx, in the second, the excess carbon dioxide is scrubbed using plants. Remember Sax Russell's encounter with this model during the Boroughs scientific conference (Robinson: Green Mars). The chief problem with this way of terraforming is the difficulty in clearing the CO2 from the atmosphere during the second stage. Time limits here are in the millennia range. He re the detailed description of the model:
The CO2 bonded into the caps and the soil is a greenhouse gas, and released by heat. If a sufficient rise in temperature (has been estimated to 9ûF) were to occur, the positive feedback inherent in this would start up a cycle leading to the release of most of the CO2 into the atmosphere, and the corresponding rise in temperatures. E.g. an increase in temperature of 10ûF would free some CO2, which would raise the temperature farther, which in turn would release more CO2, etc. Just how far the temperature would rise is dependent on the CO2 resources, and how much of them is transferred into the air. It is important to note that once the cycle has gathered momentum, there is nothing we could do to stop it. We would have to let it go on until it dies out because most of the CO2 is now in the air. Theoretically, the temperature could rise too much, actually setting terraforming back. The actual methods proposed for the initial rise of 9¡F are setting off nuclear explosives in the caps, a soletta--a space mirror reflecting sunlight onto the planet--, or building halo carbon factories to produce highly effective greenhouse gases. Nuclear detonation is disliked by the public, and will produce dangerous fallout, yet it is the only of these methods possible with today's technology. If the power truly goes over to transnational corporations, this might be the method they will choose, for its efficiency and low cost. Solettas are rather effective, and although it would be a first in space-megaconstruction, their running costs are formidably low. The initial investment required, however, is extremely high. Halocarbons promise to be highly effective, but also hard to apply. Factories would have to be built, powered and staffed on Mars. Many would be needed, as the UV radiation in the higher atmosphere splits up the halocarbons. What makes halocarbons so attractive, and needed for a greenhouse effect, is that they block energy in the so-called window: the wavelengths between 8 and 12 microns where neither CO2 nor H2O vapor have much absorption capability. Shutting this window would be useful as part of the greenhouse scheme, and vital if we ever want to stop the bombardment by cosmic rays that is currently rendering Mars a place hostile to almost every organism thinkable.
The CO2-rich atmosphere and the high temperatures (and the resulting humidity; the caps melted after all) would be an Eldorado for plants. These would now be introduced en masse to exchange carbon dioxide for molecular oxygen and establish an active biosphere. Here lies the problem: Even if there is sufficient nitrogen for the plants to live - which is far from certain - they are slow CO2 scrubs, leaving the atmosphere saturated with toxic concentrations of CO2 for centuries to come.
It may not seem likely to you that terraforming will be based on the TPM. The problem lies in the second stage, where scrubbing the CO2 seems a daunting challenge. Yet the alternative has its own share of difficulties, and the TPM promises fast warming with comparatively small effort. (University of Texas: website)
THE ONE STAGE MODEL (hereafter referred to as OSM)
This plans to approach human-viable conditions on a straight path, instead of the overshoot&backtrack strategy of the TPM.(Robinson: Red Mars + Green Mars) While increasing temperatures, it will make specific effort not to kick loose the CO2 cycle, requiring it to have continuing CO2 absorption, to keep the content in the atmosphere below the threshold of the runaway reaction. Due to the inefficiency of CO2 scrubbing methods, this forces the pace to be rather slow, to allow for sufficient absorption of the greenhouse gas despite continuing out gassing and further temperature increases. The increase of temperature, by whatever means, must be painstakingly regulated. As such, the OSM has a rather shaky balance. Once some of the CO2 has been released, repeated reassessments of deposits as well as tremendous mathematical calculation must be invested to arrive at the new temperature threshold. An error in the surveying or the calculation model might lead to the initiation of the carbon dioxide cycle, especially if a meteorological event would happen to influence temperatures.
Another problem that the OSM faces, is that in order to thicken the atmosphere without allowing CO2 to reach high levels, other gases are needed to supply pressure. And O2 is also out, because it is not inert. If the atmosphere were to consist of, say, 80% O2, a match could probably cause the entire planet to go up in flames. O(atomic oxygen) is totally unacceptable, since it is so active that it would just react with everything -human skin, walker fibres, habitats, etc. It simply wouldn't last. Inert gases that might be on Mars in sufficient quantities are nitrogen and argon, yet we cannot be sure with either. H2O might come to constitute a certain percentage of the air, but it can only remain airborne for long in higher temperature and pressure, i.e. where an atmosphere already exists. We will have to wait for further exploration to clarify whether or not there is nitrogen and argo n is sufficient quantities on Mars. If not, certain bacteria might be capable of fixing either of these from existing material. A very interesting idea has recently surfaced, and it promises close to unlimited amounts of iron and oxygen. The idea is to split the ferric oxide, the iron rust, that covers the entire planet. This simply requires heat, but heat in amounts that are only industrially available. This means that we would have to establish a functioning plant, with a power source and probably a construction&maintenance crew. And the net oxygen output of the plant(s) would have to be quite humongous to make a difference. It really faces the same difficulties as establishing halo carbon factories on Mars. (World&I: Terraforming Mars) As for the necessary raise in temperatures, two of the solutions used in the TPM are applicable: The soletta and halocarbons. However, without the dramatic help of CO2, more futuristic methods have to be considered if Mars is to be terraformed in any reasonable amount of @time. So-called moholes--vertical holes of 10-15km depth drilled through the lithosphere-- are promising, gassing out heat from the lower lithosphere of the planet into the air. However, drilling technology would have to advance a long way before such endeavors are feasible.
After the first stage of the TPM, and during the only one of the OSM, organisms would have to be introduced to Mars. These would have the purpose of scrubbing CO2 from the atmosphere, as well as providing some rare materials, noticeably oxygen and nitrogen. There's something more to those two than just breathing and providing and inert gas for atmospheric pressure: Some of the oxygen will be trioxygen: ozone. This will help in damming the flow of solar wind through the Martian air. Unfortunately, Fluorchlorinecarbonhydrates (dt.: FCKWs) are also on the list for artificial greenhouse gases that might be considered, and as everyone knows, they attack ozone. We will have to pay attention that several efforts don't run into each others ways. With nitrogen, there is an important distinction between two forms of it: N2 and NH3. N2 is atmospheric oxygen, and the triple electron pair-bind explains why it is so inert. NH3 is the version that serves as fertilizers, and it stand to reason that it is of high interest for the establishment of a biosphere. However, the firmness of N2's bind makes it quite hard to transform N2 into NH3; only certain bacteria and industrial-chemical methods can accomplish this. We do not have an industry on Mars, and so we have another kind of bacteria that might well be needed. (SciAm, Aug 99, Wonders: Dining on ammonia). But there are also positive news: A bacterium has been discovered which is most likely capable of surviving on Mars as it is. Methanobacterium wolfei is a methane-fixing anaerobic bacteria that is capable of coping with the lack of water and other harshnesses encountered on Mars. (SciAm, Aug 99, In Brief:Mars on Earth) Methane is CH4, which means that it needs C from somewhere. If it could somehow be made to take the C out of a CO2 molecule, and re lease the O2, that would mean a big step forwards. In fact, you'd be surprised what bacteria on earth can already take. Some species will laugh at -100¼C, and continue to reproduce. Cross-breading such hardship-bacteria for the traits needed on Mars is blissfully simple, the more so as many of a bacterium's traits are not encoded in the core genome, but rather in little free-floating rings of DNA called plasmids. These are routinely exchanged between bacteria, and even between different species a plasmid transfer is no rare event.
The release of bio-organisms on Mars might become an option sooner than the Mars trilogy might suggest. NASA is currently perpetrating a down-to-the-bones minimalist landing scheme termed Mars Direct. The idea is to employ today's multistage booster rockets to deliver a return vehicle, whose fuel for the trip back will be refined from the Martian atmosphere. 2 years later, when Mars and ª Earth are close again, a manned space capsule, comprising a crew of four, would be sent on the journey, landed on Mars and would stay there for 18 months before returning. A second return vehicle, delivered shortly after the manned capsule, would serve as a fail-safe and prepare the next mission, which would again be accompanied by a return vehicle for the third mission, etc. There is absolutely no aspect of this plan that requires anything beyond today's technology or budget, and even the very first return vehicle might release a selection of microbes on Mars. Bio-terraforming might enter the operation stage within the next 5 years, and it is time to get a grip on it. (Dr R. Zubrin: The Case for Mars: The plan to settle the red planet and why we must)
First off, we must discard the notion that what is done here is science-fiction or theoretical work. Mars is coming, and it looks like it's coming soon. Different from Luna, Mars is a real planet, which is inhabitable, and might already be inhabited - bacteriological life is not at all out of the question. While it will be a long time before humans in serious numbers will arrive there, a few select ones may arrive there pretty soon, and some of them might even stay. Because of the time scales commonly attached to terraforming, we should take the very first opportunity we get. Options are the release of terraforming microbes on the surface, as well as deploying a soletta, something that is currently not in our reach, but is not more than about a decade off. Because of the methods we have available, it seems likely that the TPM will be implemented, simply because we cannot support the kind of careful balancing that the OSM requires. We do not have the assets on the surface. Until we can land significant numbers and industrial machines on Mars, we have to rely on Mars to do the work for us, something which can be most easily done by triggering the CO2 cycle, and then leaning back, introducing some bacteria along the way (which can be done by a single unmanned heavy-lift rocket equipped with a MIRV). Because of the repercussions of the TPM, we should make clear decision between the two models before we initiate anything. For as soon as the cycle gets rolling, five words say it all: You can never go back. ADDENDUM: The Millennium Foundation Spearheaded by Marshall T. Savage, this is a private organization dedicated to leading mankind to what they perceive as our destiny - the colonization of the galaxy. Here a short overview:
Stage 1: Aquarius Using a seed ship equipped with a machine to generate power from the temperature difference of surface water to deep water, as well as various methods to extract raw material directly from seawater, a floating city called Aquarius will be established. It will serve to test algae-based food (a foundation for the entire endeavor), give the Foundation the financial means for the next stages, and enable the construction of further seed ships, that will build a total of 1,500 floating colonies, which output enough power and protein to meet the current world demand almost on their own.
Stage 2: Bifrost With the money and power from Aquarius, the Foundation will build a subterranean mass driver in Kenya, whose end is at the peak of Mt.Kilimantjaro, already above half of the atmosphere's mass. Manned spaceplanes launched from there will be further proprelled by massive laser arrays vaporizing blocks of ice at the rear of the plane. Assuming an operation time of 25 years, the Foundation could charge everybody half the normal launch cost, and still generate enormous profit. Also, it enables the building of its spacestation.
Stage 3: Asgard Asgard is a big, gold-coated bubble, protected from radiation by a surrounding sphere of water 5m thick. Inside, it is partitioned into 13 smaller bubbles, which are in turn partitioned. Despite having a small diameter, Asgard will offer tremendous space. Its food supply consists of synthesized food, flavored and colored, but based on algae grown in tubes in the inner water shield. Its power is derived from free floating bubbles floating around it, that focuses sunbeams to heat water, and produce power with steam turbines. The resulting energy is then transferred to Asgard via microwave beams. Due to its position in GEO orbit, and its power output, the Foundation will most likely dominate the communication industry with Asgard, giving itself even more resources. The materials for Asgard will come from Luna or one of the earth-near asteroids. A mass driver, complete with laser array (which can be made much more powerful without the disturbing effects of an atmosphere), will be established on the moon, to support the mining settlement there, which produces oxygen and other materials. Of the asteroids, only one needs to be mined for Asgard to be constructed. The most important product is the water for the shield, which makes up about 90% of Asgard's mass. Because of the low gravity, no mass driver will be required at first. During the later stages, countless Asgard-type habitats will be built, harboring a substantial portion of the human population.
Stage 4:Avallon Expanding from the mining settlement, several lunar craters will be domed over, being built in a fashion resembling both Asgard and Aquarius. Due to the nonexistence of an atmosphere, magneto-rail transport systems will be able to operate almost 100% efficiently.
Stage 5: Elysium(Terraforming Mars) With the resources humankind has by now, this is not going to be hard. Impacting a comet on Mars will produce the water vapor to increase the greenhouse effect, which will start up the CO2-cycle. To cover the time span until Mars is entirely human-viable, domes similar to Avallon's will be built. Here is a problem I see with the plan: If the Foundation doesn't hurry up, Mars might already be fully claimed - and nobody would like them to impact a comet on their claim.
Stage 6: Solaria Using Asgard-like techniques, the asteroid belt is settled, and a mind-boggling number of bubble-habitats are deployed in the inner solar system. At this stage, humanity will number tin the trillions, and be close to reaching civilization level 2: Being able to harness all the energy of a star. Two hemispheres of solar collectors deployed around the sun (but not blocking the ecliptic) will achieve just that.
Stage 7: Galactica Using an interstellar version of Bifrost Bridge, a mass driver spanning the whole solar saytem from one end to the other will be built (this is about 3500 A.D.). It takes a capsule a month to pass through, but then the capsule has reached a speed bordering on that of light: According to Einstein, time will pass a lot slower for the passengers, reducing the trip time for them by more than a factor of ten. Reaching Alpha Centauri, the nearest star system, would become a serious possibility. Once there, people will at first live in asteroids or bubble habitats, but will eventually inhabit what planets there are.
Comment: If the foundation ever gets Aquarius running, I wouldn't see what might stop them. Of course, a nation might declare war on them, but once Avallon is completed, that is no longer a danger: The lunar laser arrays provide ample power to destroy any inbound attackers. However, Aquarius is a giant investment - it is doubtful whether the Foundation will ever be able to finance the first marine colony.