A Dutch company has advertised a program to start a human colony on Mars, called the “Mars One project.” Seeking applications by those interested in becoming one of these Marsonauts, the company published an offer in which, for $34, a person could have his/her name listed as one of the applicants. By the summer of 2013, 100,000 people had applied, demonstrating that there is great interest in the possibility of establishing a human colony on Mars. The Mars One company advertises that it will send four to Mars in 2022 and another four in 2025.
And recently, NASA just completed an experiment on the big island of Hawaii, where four people lived for four months on the basalt rock deposits from one of the island's volcanoes, in a simulated Mars-like small habitat, walked around in space suits, and tested various diets to see what might work for people on that planet. So there is a lot of interest today in human settlement of Mars and/or the Moon.
As an ecological scientist, I have long been involved in the question of how to create life-support systems for long-term space travel. In the early 1970s, the National Academy of Sciences Space Science Board asked me to run a summer study of the ecological problems of such a system. Later, I developed computer models of closed ecological systems. Actually, my curiosity about living on another planet and the possibility of life elsewhere in the universe has fascinated me since childhood, and this led to my involvement with such research projects.
I was on the external science advisory panel for Biosphere 2. Although it failed to meet its primary objective --- 8 people living for two years within its 3.24 acre system closed to the exchange of any materials with the rest of Earth--- it provided some valuable results for anyone interested in long-term space travel.
Modern ecology and related science also have a lot to offer. I can only touch on a few aspects of the needs, possibilities, and problems of such a closed habitat on Mars.
The key needs for the Marsonauts will be water, oxygen, food, energy, and recycling. Also necessary for people are about 20 chemical elements. Some of them are abundant on Mars, but even some of these would have to be converted to digestible forms---try eating rusted iron, for example, abundant on Mars. Better to get it in food, but green plants can take it up for us.
The current claim, from NASA and Mars One, is that there is enough water in the Martian soil to provide for the pioneer needs, and that oxygen will come from the water by using electricity to separate the hydrogen from oxygen. But the NASA Mars Rovers have done just one test of the soil’s water content, plus there are some estimates from indirect measurements by orbiters we have sent to the red planet. This is not enough of a test. There are ice caps at the poles, but these are a mixture of water ice and dry (carbon dioxide) ice, and from the “warmer” climes, where the settlers are more likely to live, it's a long trip just for a drink of water, probably beyond any transportation capacity these early settlers will have.
Baby, It’s Cold Outside
Although Mars is the most inhabitable of our solar system's planet, it is highly inhospitable for us. Mars, smaller than Earth, has an atmosphere less than 1% the thickness of Earth’s atmosphere, so you can't walk outside. Furthermore, it’s made up of 95% carbon dioxide – this is poisonous to breathe. Everything people inhabit must be enclosed, and if you want to go for a walk outside, you will have to wear a space suit.
Another problem: Earth's atmosphere is mostly nitrogen. There is some in the Martian air, but it's all molecular nitrogen. Us living things, including plants and algae as well as animals, can't use that form of nitrogen. On earth, a few species of bacteria convert that nitrogen to forms they and other living things can use. On Mars, either the usable forms will have to be recycled, or made from the available nitrogen in the Martian atmosphere, which takes energy.
Growing food is going to be a real challenge. The average temperature on Mars is -55 °C (-67 °F). At the equator in the summer, thank goodness, surface temperatures have climbed to about 20 °C (68 °F) at noon. The Viking landers in the 1970s measured temperatures from -17.2 °C (1.0 °F) to -107 °C (-161 °F). More recently, NASA’s Spirit Rover recorded a maximum daytime air temperature of 35oC (95oF) in the shade, and regularly recorded temperatures well above 0oC (32oF), when it wasn’t wintertime.
Crop plants have specific change-of-seasons requirements. Mars has seasons like Earth does, but the Martian year is 668 days, which might or might not confuse plants.
Some More Challenges
Mars One proposes that the 8 Marsonauts live in a closed environment of only about 2,200 square feet, about size of a modest one-family home back here, and that they grow their food in that space as well. Biosphere-2 occupied 3.14 acres. That’s 136,778 square feet.
The plan will be to grow food hydroponically — in water without soil. That is possible, a lot of water will be needed, and even 2,200 square feet will likely not be enough room, especially if the plants are going to depend on solar energy, which is much weaker there than back here. One of the most dependable foods are red algae, the kind that Japanese use in many of their foods. But a diet of mostly red algae will be tiresome and probably unhealthy.
A lot of energy is going to be needed, starting with just plain heating the interior dwellings. There are three possible sources of energy: solar energy, used by the NASA Rovers; a nuclear power plant transported from Earth; and — a long shot— local geothermal energy, which I will explain in the book.
Back on Earth, natural ecosystems require change over time, and redundancy is necessary --- more than one small plot of one kind of ecosystem --- for the life within it to persist. In a small enclosure on Mars, there will be little room for that kind of redundancy, and getting crops growing in constant conditions will increase the challenge. Several very small closed ecosystems have also been tested. Some, with just algae and bacteria and other microbes, have persisted for several decades, but they under go major changes in which species dominates.
Recycling of oxygen, water, wastes, and the minerals plants need to grow is a major challenge. In Biosphere 2, some recycling was done by having an artificial wetland --- plants growing in fresh water, which on Earth do a very good job of cleaning up sewage, taking up and storing nitrogen and phosphorus in forms that plants can use. But there may be precise little room for this.
These are just a few of the many things that must be considered to make a habitable space station. I will write more about this.