From: M.S.Coppinger@hertfordshire.ac.uk (Matt) Newsgroups: sci.nanotech Subject: Nanotechnology Date: 23 May 94 03:47:53 GMT I'am sending this article on behalf of my brother who is studying Manufacturing management at Middlesex University in England. Terraforming Mars using self replicating molecular machines By Robert J. Coppinger (ROBERT22@UK.AC.MIDDLESEX) Mars, the red planet, it has conjured up many images, mostly bloody ones, as it represented the Roman god of War. Yet in recent years more and more publications in scientific journals such as 'Nature' have appeared proposing ways of terraforming Mars. The initial problem cited for living on Mars is the atmosphere. Mar's atmosphere is presently 6-7 millibar's, less than one tenth of ours. Approximately, 3-400,000 billion tons. To have an atmosphere of one bar the mass of gas needed would be four million billion tons. (4000 billion tons = 1 mbar). For plant life on Mars pressures as low as 10mbar would be adequate, but we want humans to be able to live there, at least in the near future wearing just 'scuba diving' like pressure suits. Other factors, such as rate of rotation and gravity are not a problem. Mars' surface gravity is 0.38 g and this is adequate for terraforming. There is no deficiency in the amount of sunlight that reaches Mars, it may be only 43% of Earth's total but this is sufficient for photosynthesis, for the plants we do want to send to Mars. For human habitation, the minimum partial pressure of oxygen must be about 130mbar. If the entire atmosphere was to be only oxygen it is known that long term exposure to pure oxygen at 345 mbar (a more comfortable pressure) can be tolerated but oxygen is flammable, a major problem. With oxygen toxicity a possible problem, 300mbar is a better alternative, with a buffer gas, for example nitrogen can be used as there are possible nitrate reservoirs on mars in the soil/regolith. It is believed that problems of cosmic radiation can be overcome with a gas column mass of 390mbar and above. So we could have partial pressures of oxygen and nitrogen at 195 for each gas, giving us more oxygen than the absolute minimum, giving us a buffer gas and of course aiding the blockage of cosmic radiation. So 390mbar (or 1.56 million billion tons of atmospheric gas) could be a target value. Of course we need Mars to be habitable for humans and this atmosphere will also balance the energy budget of the planet. As on the Earth the planet absorbs and radiates energy from the sun. The atmosphere therefore must aid warming by trapping this warmth so there is a net gain from sun warming against the radiating of energy. This is known as the greenhouse affect and the temperature increase due to this is about 6kelvin. Adding O2 and N2 will increase this effect. Another way of increasing the temperature would be to add CFC's, as we have found on Earth. The CFC's, CF6, CF3CL, CF2CL2 and CF3Br can all be manufactured on Mars from elements found there. These CFC's also have long lifetimes against UV radiation damage, from the sun. One part per billion of CFC's will increase the temperature by about 0.1 kelvin. For a real temperature increase, CFC levels really need to be at parts per million, and this is not toxic and this would result in 0.01 mbar's of the atmosphere being CFC's and this requires 40 billion tons of gas. Due to UV damage there would have to be continuous production of CFC's to the sum of 100 million tons per year. UV destroyed CFC's could be reconstituted from their parts that would then be floating in the stratosphere. Unfortunately any ozone layer would be destroyed, yet much of the radiation would be deflected with the column gas of 390 mbar plus. Sources of CO2 can be found in the regolith/soil of Mars. It is estimated that the regolith contains 300 mbars of CO2. Another source is the south pole where a 350 km diameter CO2 'cap' which may be 1km thick will provide 100mbar of atmospheric pressure. One Hundred milibars will activate global sublimation, certainly in the regolith and this will in turn create a run away greenhouse effect. A necessity for terraforming is water, and this is believed to exist on Mars at levels of about 500 metres below the surface as permafrost and it is known that the polar cap is 5000 cubic kilometres of ice. The estimated amount of water that Mars has lost through atmospheric outgassing is estimated at 0.5-1 km worth of water - this is based on such water created geophysical landmarks such as the Valles Marineris. Other chemicals which are factors in creating life are sulphur and phosphorous and both exist on Mars. In order to create this terraforming process, to get it going and to see the process continue to create a habitat for humans, Mars would have to receive in a short time frame, the equivalent of ten years worth of sunlight, or 1 million joules cm-2. To convert the materials we know we can find on Mars into the gases we need to create life we would need a highly efficient conversion organism. Molecular mechanosynthesis using molecular devices is one possible answer to the huge quantities, the billions of tons that have to be produced to create the 390 milibars or even to create the 2.2 bar atmosphere that some scientists believe is necessary for Earth like conditions. Nanotechnology will give us these devices. In a recent paper given at a USA/Japan symposium on nanotechnoogy and it's affect on manufacturing the time line given for the development of nanotechnological manufacturing systems gave us, in 2010, systems that could synthesise substrate. This would appear to be a complex task, with atom deposition rates far higher than we have today. If we can produce machines with those capabilities how hard will it be to create molecular machines whose job, in reality, will be purely the disassembling of carbonate and nitrate in martian regolith and the sublimation of polar caps. In Eric Drexlers book, 'Nanosystems: Molecular machinery, manufacturing and computation', he details the design of mechanochemical machines that could do all this. Breaking apart materials at the molecular level will probably take less energy than Chris McKay's (whose last paper on terraforming Mars was in Nature in 1991) estimate of 1 million joules for the terraforming process, due to the nature of the mechanosynthesis process. Drexler, on page 63 of 'Engines of Creation' says that the dissembling machines could break down rock, thus the carbonates in the regolith could be obtained. An enzyme molecule can break down 40 million hydrogen peroxide molecules per second, therefore, under thermal agitation at 'normal', Earth temperatures the molecule 'break down' speed can be 100 molecules per trillionth of a second (mps). Clearly we need machines that can also replicate themselves from the materials found on Mars, so they can cover the planet and liberate all the carbonate and sublime the polar caps. Do we have enough material on Mars to do both, replicate and mechanosynthesize the new atmosphere? Each molecular device we need will weigh in at around, an estimate of course, 10 to the nine AMU's (atomic mass units). Even if we had 180 million billion of these machines they would only weigh 30 grams, yet their 'body weight to material-released weight' ratio could be great. On Mars it's estimated that there is 1.2 million billion tons of carbon dioxide in the regolith, 5.6 million billion tons of water (at the polar cap - so this figure excludes permafrost) and a further 400,000 billion tons of carbon dioxide in the southern 'ice' cap. The total amount of material, in terms of carbon dioxide and water only, is some 7.2 million billion tons of material. It would be safe to presume that this is enough. We do have an entire planet from which to 'mine' the resources we need. So, how long will this all take? Eric Drexler, in 'Engines of Creation', suggests that replicating machines will take 1000 seconds to replicate. These machines will have exponential growth, and therefore, Drexler calculates, after ten hours there will be 68 billion molecular machines, a mass which is about 680 billion billion AMU's or at a guestimate, the mass of machines would weigh in at 120 kilograms, I think? Drexler claims that within 24 hours there will be almost one ton of replicating machines. Drexler estimates that after two days the replicating machines will have gained a weight equal to that of Earth. Clearly there's no argument as to their ability to organise materials and to replicate in vast quantities, we just need them to manufacture the CFC's and the oxygen and nitrogen and the carbon. The quantities that are needed are vast, estimates are for some four million billion tons for an atmosphere of one bar, or for an Earth like, purely CO2, atmosphere you need 2.2 bar or around eight million billion tons. You could have a variety of different machines, three types, say, one type for carbon dioxide, another for nitrogen and finally one for oxygen. For the target atmosphere value of 390 milibars and the CFC's needed to aid warming we need a total of, and this is a safe estimate, of 2 million billion tons. Far less than the eight million billion suggested earlier. We do not want a mass of machines that weighs as much as the Earth, so we would need a death program, we would need a stable population of machines that would give us a stable, productive rate of gases. If the replicating machines could become a mass of a ton or more after twenty four hours, then we could aim to produce enough machines which could manufacture the atmosphere in twenty years, using a 'death' program to keep the total machine mass and production rates stable. Therefore to produce 2 million billion tons after twenty years or 175,200 hours we would need a production rate of eleven billion tons an hour. As pressures began building to our target value the molecular machines could be programmed to self destruct and dissolve. Twenty years, within a life time, within a generation, where as other periods for terraformation given are in the order of 300 years. Twenty years and there will be lakes and seas, an atmosphere which will last for thousand of years and there will be large amounts of 'dead' molecular machines, which could be programmed as a part of their 'death' process to become top soil for a planet. The Valles that exist on Mars could be filled with water and the canals that Lowell saw would be a reality. But the only intelligent life there will be human life. Mars will become alive, it will be, life from lifelessness, literally, Genesis.