The general layout of each City is shown in fig. 6: the plan involves a main conglomerate, housing administration and where the bulk of the population lives and works. Mining and exploration sites are located at varying distances from the City, depending on variables such as the availability of local resources and geologic interest: these are supplied with foodstuffs and water directly from the City, and have some limited capabilities about power supply and water. A large space launch complex is located nearby and serviced by an underground shuttle: this site is supplied directly from the Cities concerning water and other consumables but possesses independent life support and power supply. The rocket fuel production industry is housed in the main conglomerate. The tourism infrastructure centers are located close to each site of interest, and thus are widely scattered. Exploration and geologic prospecting centers generally reflect momentary needs of scientific and economic plans and are by design mobile and flexible: they lack complex, permanent infrastructure. Mining sites are widely scattered over the planet and always reflect specific places where resources are being extracted, such as nitrogen, aluminum, and phosphorus. 


FIGURE 4 – Surface mineralogical composition [4][5] of the Persbo crater region at Cerberus Fossae (left) and the Guaymas crater region at Chryse Planitia (right), color coded is as follows: sandy color: smooth plains made of eolian deposits; light orange: crater plains made of lava, coated by loess; dark orange: belted plains with lava channels; dark green: fluvial and eolian deposits; light green: breccia material, subsurface collapse of ground ice melting; red: plains with lava channels; dark gray: knobs: orogen relics, relief inversion and subsurface collapse, containing ejecta; light gray: canyon floor material of the Vallis Marineris: fluvial and eolian sediments, landslide material, possibly partially exposed bedrock; violet: hilly lava plains; brown: lava plateaus covered by breccia like ejecta; pink: aureole material: lava flows from fissures.

FIGURE 5 – map showing the estimated locations, and corresponding uncertainty ellipsoids, of two important seismic events as detected by the NASA Insight mission, S0235b and S0173a [7], right in the middle of the Cerberus Fossae fault system. This is regarded as one of the youngest tectonic features on the surface of Mars, linked to possible recent volcanic activity and tectonic stress. Persbo crater lies slightly to the west of the S0173a event, to the southwest of the major fault system of Cerberus.


Each conglomerate is divided into an administrative, working and storage area plus three autonomous units (dubbed AUs, figure 6), each containing life support machinery, living quarters, some limited storage capacity, and indoor recreation. The independent design reduces the risk of catastrophic loss in the event of epidemics, meteorite strikes or other hazards, since each AU is designed to perform in essentially independent way from the other AUs. Each AU houses roughly one third of each City´s population. In figure 7 we show additional details of the design, as nested inside the paraterraformed craters. The design seeks to minimize radiation exposure for personnel above ground: such exposure is an ever present and critical concern, strongly mandating working and living quarters to be placed underground. The paraterraforming enclosures offer additional protection, and the City State design makes clever use of the walls of deep craters, by having structures close to the inner crater rim, thus obtaining extra radiation protection from the regolith for particle incidence angles up to 45 degrees (fig. 7) [note: dimensions in fig. 7 concerning either height of crater rims and central peak, or depression of crater floor, with respect to the datum, are merely illustrative and can vary by large factors for different craters].

Suitable crater sizes for the paraterrafomred design were estimated as follows. Each City is fully contained – the urban model is that of a large city on Earth. We take the suburb of Copacabana, in Rio de Janeiro, Brazil, as a fine example of a heavily urbanized and quite self-contained community (two of the authors possess lifelong experience with this type of community), with very diversified commercial activity, including hospitals and medical services, plus recreation and sports areas. It is a very verticalized community with a high density of buildings, populated in 2013 by 150,000 people, officially in an area of 7.84 km2. We round these number off to their orders of magnitude: 105 people living in 10 km2. We assumed for the City State a similar verticalization, where buildings translate to underground structures down to some tens of floors. Extrapolating to 500,000 people for each City, a crater with 50 km2 is needed for each, translating to a diameter of 8 km. Larger craters allow for lower population densities, which is desirable, but initial versions of the City State may have to cope with somewhat high population densities. Relaxing this constraint to the next order of magnitude, one-tenth of Copacabana’s population density translates to an area of 500 km2 for 500,000 people, and we further allowed for agricultural and recreational areas: the corresponding crater diameter is ~25 km. Suitable craters lie in the 10-30 km size range, available at both the Cerberus Fossae and Chryse Planitia sites. We further validated these numbers considering São José dos Campos, a very prosperous Brazilian town, known for having a large share of Brazilian aeronautical and space industry and research centers. Its population of 630,000 people sprawls inside ~1100 km2. This town includes heavy power plants and various important Brazilian industrial facilities: such a town could fit inside craters with diameters less than 40 km.


FIGURE 6: (left) general outline of the two conglomerates of Koemitan/Nahootsoii, and their relationship to other activity sites; (right) general plan for each population conglomerate: AU stands for “autonomous unit”.

Sustainability on Mars: the Ethanol Cycle Case for Koemitan City and Nahootsoii Town

In the recent film “The Martian”, the astronaut Mark Watney, played by actor Matt Damon, gets stranded on the red planet, facing the ominous prospect of death by starvation, since the food supply of the base, used by him and his colleagues, would not last until the arrival of a rescue mission. Unfortunately for him, the base was not designed to be sustainable, that is, to be able to sustain life using the free energy of sun light and recycling raw materials.

Fortunately, he remembered that there were still some potatoes available, and plenty of organic waste, conveniently sealed in plastic recipients, from the team that shared the base with him. He used it to fertilize Martian soil with organics and microorganisms, and started a potato plantation. His idea extended his life time and was key to a successful rescue.

This is a good example (and in an appropriate locus!) of sustainability techniques, which have been employed and perfected by Earth’s biosphere for billions of years, despite the universal and annoying third law of thermodynamics. They involve Photosynthesis and (with the indispensable aid of microorganisms) Recycling. That´s why any potentially prosperous Martian colony must include these elements. On Earth, for example, forests and other large ecosystems are able to thrive for millennia, despite the shortage, in rocks, of one fundamental element for life, namely Phosphorus. Recycling phosphorus with an almost unbelievable efficiency is the key. In the words of Tim Lenton(1):

“Phosphorus in dead organic matter is recycled by bacteria and fungi, including the mycorrhizal fungi that are directly connected to plant roots, limiting the possibility of losses along the way. The average terrestrial ecosystem recycles phosphorus roughly fifty times before it is lost into freshwaters.”

Even the lost phosphorus is appropriated by aquatic ecosystems. 

The role of photosynthesis also involves recycling, this time carbon recycling, through removal of carbon dioxide from the (Earth’s) atmosphere, and the oxidation of the products of photosynthesis, either by the consumption of plants by other organisms or by the decay and death of plants and plant parts (leafs for example). There are many vital feedback and recycling systems in Earth’s biosphere, and the diversity of organisms (biodiversity), each specialized in a way that contributes to the whole, plays a key role in the general sustainability. To mimic such a complex system in a colony environment, in a way that it can be called sustainable, is no easy job.

On Mars, outside any colony boundaries, the environment is quite uncooperative in terms of processing and recycling of vital inputs for life, since it is dead, a fact predicted by Lovelock back in the sixties, by studying the composition of the Martian atmosphere(2,3). He concluded that it is in chemical equilibrium, and therefore there is no life on the surface of the red planet. Even if there was life of any sort, chances are that its biochemistry would be completely incompatible with that of Earth’s biosphere.

So, except for raw inorganic materials, the Martian environment will not be a player in the sustainability scheme of any colony. I am, of course, considering that the sun light is an external source of energy. And, since the size of a colony, even in a scale capable of supporting a million people, will probably be small to be completely self-sustainable, it will, in the long term, need key supplies from outside, which is not to say that it is not sustainable.

Figure 2 shows the general life sustaining fluxes for our design of Koemitan City and Nahootsoii Town, which follow the concept of Autonomous Units. They strive to maximize recycling, and includes an interplay between industrial materials and organics. It uses Martian atmosphere, Martian soil and ores, and Martian water in order to make air, water, food and materials for human consumption. Since there is no perfect life sustaining system, periodic purges to the external environment are necessary.  The sources of energy are deliberately diverse, in order to provide robustness and flexibility to the colony.

The design of the Autonomous Units does not pretend to solve the myriad problems regarding sustainability, it does introduce a novelty, namely, the Ethanol Cycle.

While CH4 production for rocket fuel by a catalytic process involving CO2 and H2  is a well-established idea(4), its use in internal combustion engines for transport, inside and outside the city’s boundaries, is not the best choice, compared with an alternative which is liquid at room temperature and pressure and handles almost exactly like water, besides having a high calorific power.

Even better, this alternative comes from a renewable bioprocess that is easily integrated within the ecology of the city and its life supporting systems (Figure 3). Such a process has been in use on Earth, in industrial scale, for decades: ethanol from sugar cane, an important fuel source for automobiles in Brazil(5). The high productivity of sugar cane(6,7,8), compared, for example, with ethanol from corn in the USA, the recycling of the subproducts of the industrial process, including the production of thermal energy (Figure 3), and the closure of the CO2–photosynthesis-oxidation-CO2 cycle makes it a great option for Koemitan-Nahootsoii.

The Brazilian production of ethanol from sugar cane has been praised worldwide as a green and efficient fuel production(9,10);  Tables 1, 2 and 3 show recent data on sugar cane, sugar and ethanol production in Brazil.

The only weakness (on Mars) of this cycle is the necessity of plenty of sunlight for the plants to grow, a problem solved by introducing genetically engineered varieties able to thrive under less sunlight. Sugar cane ranks already quite high in the plant realm as concerns photosynthetic efficiency, so there might not be much room for genetic improvement: also, sugar cane may require higher atmospheric pressure than most crops to attain maximum yield; at worst, one might have to operate with sub-optimal yields.

This industry produces surplus energy from burning the dry biomass after milling, and this extra heat goes into distillation. However, since he calorific power of the burn is larger than needed by distillation, an adjacent thermoelectric plant generates electricity (as is standard practice in Brazil, where generated electricity feeds the electric grid), which in turn is used to power electric lamps along the plantation area.  These lamps are managed to alleviate or overcome periodic blackouts of sunlight during prolonged dust storms. The ethanol is employed in combustion engines to power land vehicles, but only for open-air use (outside the paraterraforming enclosure). Some water from this combustion is reclaimed and brought back to the City, while CO2 is simply vented back to Mars’ atmosphere as exhaust. The lamp system consists of high-efficiency LEDs with emittance heavily concentrated between 430-530 and 640-690 nanometers, the spectral range where chlorophyll A and B have the highest absorbance, hence lending the highest possible photosynthetic yield.

One key player in the Ethanol Cycle is the microorganism Saccharomyces cerevisiae, a fungus that is best known as the producer agent of beer and wine, again by fermentation, and bread (backing). Nowadays, this yeast has been used to produce medicines, such as hormones (including insulin)(11). It is arguably humankind’s best friend, as microorganisms go, and is also widely used as a model for studies of biochemical processes and diseases in humans.

It is then only natural that S. cerevisiae, along with many other microorganisms necessary for soil fertilization, for example, be our partner on Mars, in order to contribute to a healthy and sustainable colony.