Mars colonization and its many obstacles have been a hot topic these last years. Many solutions proposed to overcome the problematics of colonization involve the use of microbes, and especially microalgae. Let’s see how they can help!
You may think, what makes microalgae attractive to scientists?
At a general level we can highlight that microalgae can:
- Accumulate more reserve compounds when compared to traditional cultures.
- Recover phosphorous and nitrogen from wastewater.
- Produce oxygen and consume carbon dioxide via photosynthesis.
- Be cultured under conditions in which plants from conventional agriculture cannot survive.
- Supply nutrients to organic-degrading bacteria.
It is likely that you have heard the term “microalgae” from Chlorella extracts used as food supplements. In our case we refer to living cultures! Also, whenever we talk about microalgae we include both prokaryotic and eukaryotic algae.
But let’s go back to the colonization of Mars… Which basic needs in space or Mars can be solved by microalgae?
- Food collection: Although human diet must be varied, microalgal biomass can serve as food. This biomass is rich in essential oils which aside from nourishing help to mitigate the strains of microgravity and cosmic radiation during space travel.
- Oxygen production: Nothing is more essential to survive than an adequate oxygen concentration in air. Microalgae and especially cyanobacteria (prokaryotic algae) are great oxygen producers during photosynthesis.
- Nutrient recycling: In an almost-closed self-sufficient as the one planned for Mars colonization, nutrient recycling must be done in an efficient way*. Microalgae assimilate carbon dioxide in the environment to synthetize nutrients and recover phosphorous and nitrogen that we excrete through urine. If we engineer these capabilities, we can obtain purified water to be consumed again.
- Protection against radiation: The radiation in Mars surface is much more intense that the one we experience in Earth. Solutions to this problematic include buildings made of transparent recycled plastic with an inner layer of water in its walls to culture microalgae. This algal biomass would protect homes from radiation and at the same time it could feed from it. Excess biomass could then be harvested to obtain food for people or feedstock.
*You just need to imagine what would happen if urine was not recycled in Mars or during the space travel. The necessary water would occupy 80-90% of the spaceship, at a cost of almost 20.000€ per L of water. It would be nonsense to constantly send water at this cost to Mars.
The last (or first) step towards Mars colonization could be creating a favourable atmosphere like the one in Earth. Hence, the concept of “terraforming” that implies transforming the environment, so humans can inhabit the planet surface without need of air cylinders or astronaut suits. Among the long list of challenges to attain this, we will only talk about oxygen in air. It would be necessary to raise oxygen concentration up to 21% as in Earh and the process using microalgae would take at least some hundred million years. It is believed that the atmosphere only begins filling with oxygen once the other main reservoirs are full. Thus, lithosphere and biosphere (which contain 99.5% of the oxygen in Earth) should be saturated first. In contraposition, atmosphere only amasses 0.5% of the total oxygen (Walker, 1980).
As you might have guessed, phototrophic microbes would be the candidates for this job as they produce oxygen more effectively than any plant. Cyanobacteria were the first to contribute 2.4 billion years ago while eukaryotic algae didn’t appear until 2 billion years ago.
Despite the interest of the proposal, actual technology cannot provide a viable terraforming process. Any climate change is based on the greenhouse effect produced by accumulation of carbon dioxide in the atmosphere, but Mars has a low atmosferic pressure and cannot retain enough carbon dioxide to trigger a greenhouse effect..
- J. Masojídek, G. Torzillo (2014) Mass Cultivation of Freshwater Microalgae. Reference Module in Earth Systems and Environmental Sciences, Elsevier, ISBN 9780124095489, https://doi.org/10.1016/B978-0-12-409548-9.09373-8.
- JCG. Walker (1980) The oxygen cycle in the natural environment and the biogeochemical cycles, Springer-Verlag, Berlin, Federal Republic of Germany (DEU).