Terraforming Mars – Part 4

photo by Kevin Kelly, from asiagrace.com

This is the final part of a series on the obstacles to be overcome in the process of terraforming Mars for human colonization. The previous articles covered thickening the Martian atmosphere, warming it to comfortable levels and transforming it into breathable air. This section will cover the details of building structures on Mars, as part of creating a self-sustaining human colony there.

It can be assumed that some humans would be on Mars for most of the terraforming process, following the orbital bombardment stage. Initially, the planetary engineers and early colonists would live in their spacecraft and in prefab habitation modules brought from Earth, but soon construction would need to begin on permanent Mars structures. Since there are no forests existing yet on Mars to harvest, nor any cement factories, structures would need to be constructed with the available material. On Mars, rocks and dirt are plentiful, and similar materials have been used for building on Earth for thosands of years. Examples of this construction includes caves, stacked & mortared stone, adobe and rammed earth. More modern examples include cast stabilized earth, earthbag structures and excavated underground spaces. Let’s begin by looking at the basics of each of these systems.

Caves were the first housing for humans, as this shelter solution was as simple as finding a hole to live in. Natural caves, if any exist on Mars, would be a suitable initial shelter for some aspects of Martan colonization. They likely wouldn’t be suitable for most of the structures needed as it would be limited in location, size and ease of access. Underground habitation is a desirable option however, so excavation of artificial caverns will likely be used more than natural caverns.

Excavation of underground spaces is very common on Earth, both with humans and many animals. Underground construction has many benefits such as a more stable temperature, very secure and stable surroundings, and protection from solar radiation and micrometeorites. On Earth human underground construction is accomplished with large equipment that digs holes, explosives that break up rock, and conveyance systems to remove the debris. This would be a little more difficult on Mars, so a different approach would be required. Since protection from above is the goal, simply digging a hole wouldn’t be sufficient. Spaces would need to be created as tunnels that were expanded to form caverns. The logical choice for this is a mining device called a roadheader. A roadheader consists of a treaded body with an extending boom that sweeps across a rock face with a cutter head. Large roadheaders are capable of removing about 40 cubic meters of rock before moving the base forwards. Recent advancements in mining technology have produced automated roadheaders, capable of selectively cutting rock faces to extract valuable ore while ignoring the rest of the rock. While mining for metals would definitely be a useful practice on Mars, the biggest benefit of this technology would be creating underground spaces automatically. Once a suitable area was selected, deep penetrating radar or acoustic sounding could be used to produce a 3D model of the underground area being studied. A computer model would then be created that would contain the desired space, and the robotic devices would set to work excavating the space. Since there are no conventional fuels on Mars, the equipment would need to be powered electrically, with power derived from solar sources. Nuclear power would also be a possible option for the automated equipment, but there are several serious issues associated with transporting the equipment to Mars as well as maintaining it once there. With solar electric equipment, excavation would continue as long as sunlight was hittting the solar generators, and could continue each day until the project was finished. Since automated roadheaders don’t need a warm oxygen-rich atmosphere to operate in, this could start fairly early on during the terraforming process so when humans were ready to move to Mars, an incredible amount of space would be ready to use. Periodic maintenance would be required on the equipment to replace cutting heads, but it may be possible to eliminate the cutter heads completely. If advances in nanotechnology continue at their expected pace it may be possible to use nanomachines to break down the rock at the molecular level, seemingly melting it away as if it were butter touched with a hot iron. Whatever method is used to excavate caverns, there will be a tremendous amount of waste material produced, in the form of dust and rocks. This is actually an advantage, because this material can be used to build surface structures.

Surface structures are the most common type of structure used by humans, because they’re easy to construct, easy to access once built, and provide access to natural light and air. Since the initial structures on Mars will be designed to protect against the planet’s air, access to light and ease of construction are the positive points. The structures need to be airtight, so right away stacked stone is ruled out as a possible construction method. Even with mortar, this would be difficult to automate due to the irregularities with the stones. The next option used on Earth is stacked adobe bricks, which was the first attempt at making synthetic stones. Adobe bricks are essentially sun-dried blocks of sand and clay, and perform very well in warm dy climates. Adobe blocks have excellent thermal mass, meaning they resist quick changes in temperature by storing heat during warm times and releasing it slowly during cooler times. On a daily cycle on Earth adobe houses stay cool during the day and warm at night because by the time the blocks start heating up during the day, the sun has already gone down and the blocks begin cooling down again by releasing heat. This would be an advantage on Mars due to the large temperature swings the planet experiences. As the atmosphere thickened and warmed, this would become much less of an issue but would always serve as a means to regulate heat passively, thus saving energy.
Formed blocks is the evolved version of adobe blocks, and has the advantage of a more uniform shape and size. In 1952 a device was invented called a Cinva Ram that allows for the rapid creation of compressed blocks of soil which are strong enough to be used for multi-level buildings. This process involves putting a measured amount of material into a block maker and then applying sufficient pressure to compress it to a block. This process could be automated as well, resulting in colony infrastructure being built slowly by machines while the planet was still being terraformed. With human operators, a Cinva Ram can produce up to 1,000 blocks per day. By automating this process the output could be increased. With automated block creation and construction running every day for several years, entire cities could be built ready to be inhabited once the planet was ready. By siting these block makers near excavation sites, the excavation waste could be pulverized to provide much of the block material. This isn’t the only use for this excavated material, similar material is being used to quickly build structures on Earth using the “superadobe” or earth-bag process.

Earth-bag construction is a method where bags or tubes, commonly made of woven polypropylene, are filled with dirt, small rocks, or other finely ground material and coiled to produce dome shapes. As each layer is laid down, it is compressed to compact the material inside. This building method was developed by architect Nader Khalili at the Cal-Earth Institute and would be ideally suited to Mars structures as the materials required are lightweight and strong, and require only the addition of compactable particulate matter. Domes are a very strong structure and could be buried to provide further protection from the Martian climate. Many shapes can be produced with this method, including vaults and corridors. A stabilized plaster would be created from the fine soil to cover the walls and produce a useable interior and exterior finish.

The last two remaining options for basic construction are rammed soil-cement and cast soil-cement. The concepts are similar in that they both involve a soil mixture being put into forms to create walls but that is where the similarities end. The rammed soil method is a very old technique, in fact the Great Wall of China was constructed with this process. The technique mimics the natural process of sedimentation and produces very strong monolithic structures. Soil is mixed with a small amount of water and often cement as a stabilizer and shovelled into the forms. Traditionally the process used workers with weights on the end of poles to hand tamp the soil mixture; in modern construction pneumatic tampers are used to speed up the process. Cast earth is a newer technique which uses a slurry of soil, water and a gypsum mixture that is poured into wall forms to dry and harden. The cast soil requires a gypsum mixture to stabilize the slurry that is formulated based on the soil used, so this would be harder to utilize initially on Mars. Once the climate was habitable enough for humans to work outside for extended periods of time however, cast and rammed soil would be excellent options for building structures that required shapes other than domes or vaults. Once mining commenced and metals were produced, more traditional buildings could eventually be constructed.

The entire terraforming process should take around a century, during which time technological advances on Earth would be occurring in the areas of energy production, nanotechnology, food production and every other aspect of our society. Regardless of the details of how a Martian colony would operate, one thing is certain; a new method of timekeeping would need to be established that was capable of relating to events and times on both planets. A standard interplanetary calendar would address this issue, and allow for Terrans and Martians to have a standard timekeeping format that could be referenced in addition to the planet specific time periods, the same as we can convert currencies or temperatures.

Many of the sustainable practices being developed here on Earth would be implemented on Mars because there are very little resources there. Every part of the colony would need to be carefully planned to account for this, but this would serve as an opportunity to create a completely new model of human civilization, doing things right from the very start. To me, that is a very exciting proposition.

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About

Steve holds a degree in Environmental Engineering Technology from Humber College in Toronto, is a LEED Accredited Professional and a Certified Sustainable Building Advisor. He currently lives in Victoria BC and works as a green building consultant specializing in residential projects.

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