This story was originally published in the MIT Reader's Newspaper.
Exploration, habitation, and resource extraction all have the risk of causing damage to the space environment, just like on Earth. But some futurists and space settlement enthusiasts have proposed a more drastic change to the space environment: transforming the surface of a planet or moon into a more Earth-like environment through a process called terraping.
By design, the atmospheric chemistry, pressure, and temperature within the man-made space habitat are similar to those of the Earth and sufficient for human habitation, but it needs to be enclosed and maintained by pressurized walls. Terrain formation will affect the entire surface of the planet, not just a smaller "indoor" area. According to planetary scientist Christopher Mackay, the environment in which the terrain forms a planet "must remain stable over a long period of time and does not require or at least sustained technological intervention." "After the initial energy and effort, the environment formed by the terrain will behave like the natural environment of the Earth and essentially hold itself.
For example, in 1961, Carl Sagan speculated on the possibility of "microbial reconstitution" on Venus by introducing blue-green algae into the atmosphere of Venus. Algae will use photosynthesis to convert Earth's abundant carbon dioxide into oxygen, which will also reduce the greenhouse effect and lower the surface temperature of Venus. Sagan later turned his attention to the potential to "redesign" Mars, a planet that is now considered one of the best candidates for our successful terraforming. Mars has the opposite problem with Venus: instead of sheltering a thick, toxic atmosphere that creates an uncontrolled greenhouse effect that maintains extremely high surface temperatures and pressures, almost the entire primordial atmosphere is blown away by the solar wind, making the surface pressure too low for liquid water to exist. To terraform Mars, planetary engineers need to increase Martian surface temperature and atmospheric pressure while protecting the atmosphere from the solar wind. Sagan suggested spreading a dark-colored substance on Mars' polar ice caps, or even planting dark-colored plants, to allow them to absorb more of the sun's heat and raise surface temperatures while releasing water vapor and carbon dioxide into the atmosphere. Other researchers have explored the feasibility of importing greenhouse gases or building giant orbital mirrors to raise Martian surface temperatures, building magnetic shields to protect the Martian atmosphere, and releasing genetically engineered microbes to the Martian surface to alter the atmosphere and surface chemistry.
TerraFormation is the ultimate example of long-term planning, even with optimistic estimates, and it will take centuries of hard work and patience for humans to walk unprotected on the surface of Mars. Advocates of modifying the Martian or other space environment see this as a crucial step in creating a truly multiplanetary civilization. Robert Zublin, founder and president of the Mars Society, which advocates for human exploration and colonization of Mars, even claims that a successful terraforming of Mars will prove the superiority of humans over the physical world: "The first astronauts to arrive on Mars will prove that human life can go to heaven." But if we can terraform Mars, it will show that heaven itself is subject to the intelligent will of man," he wrote in his 1996 book, The Case for Mars.