Occupy Mars
Although only a handful of visionaries are currently committed to the Mars colonization program, the majority of Americans appear to support this mission. According to a YouGov poll conducted in June 2025, 65% of respondents approved of the United States sending astronauts to Mars. However, it should be noted that a Pew Research survey at the end of May 2023 showed that other space projects are more important to American adults: when asked what NASA's top priority should be, Americans ranked monitoring asteroids and other celestial bodies that could hit Earth first (60%), while sending human astronauts to explore Mars came in last (11%).
Why does Mars attract such special attention from Elon Musk and those visionaries who hope to turn humanity into a multi-planetary species? Other planets and moons in our solar system are either too far away, too hot (Venus has a temperature as high as 860 degrees Fahrenheit!), or too cold, and as far as we know, none of them have conditions suitable for colonization like Mars. So what exactly makes Mars more suitable as a colony than other celestial bodies in the solar system, and what challenges still need to be overcome?
Multiple uncrewed Mars missions, including NASA's deployment of the car-sized remote-controlled robotic laboratory "Curiosity" to land on Mars in 2012, and "Perseverance", which has been searching for signs of ancient microbial life on Mars since 2021, have presented us with a detailed picture of the planet. Water is a fundamental condition for human survival and agricultural activities. Due to the extremely low surface temperature and extremely low atmospheric pressure on Mars, water cannot exist in liquid form, but exists in the form of ice. Multiple missions, including the European Space Agency's "Mars Express", have discovered large amounts of water ice in the polar ice caps and higher latitudes.
In July 2018, the first reports of possible underground saltwater lakes on Mars emerged one after another. Roberto Orosei and his team published their research findings "Radar Evidence for Liquid Water Beneath Mars' Ice Caps" in the journal Science. Using radar instruments on "Mars Express", they detected an unusually bright reflection signal about a mile below the Antarctic ice sheet, indicating the existence of a large body of water about twelve miles wide there, whose characteristics are completely consistent with liquid salt water. Further investigations in 2020 found three smaller underground basins near the main lake, which is now estimated to be about nineteen miles wide. Other ground-penetrating radar observations show that the northern region of Mars is covered with a large number of huge glaciers made of pure water ice, covered with only a few meters of dust, extending south from the polar region to 38 degrees north latitude — a latitude that exactly corresponds to Athens on Earth.
Frozen water on Mars can be extracted, melted and purified to produce drinking water, oxygen (via electrolysis) and even hydrogen fuel. Experiments conducted by NASA and other research institutions have shown that plants can be grown in special greenhouses simulating the Martian environment. Martian soil, composed of regolith, contains many key minerals required for plant growth, such as phosphorus, potassium, and magnesium. However, the presence of perchlorate, a toxic salt harmful to both plants and humans, poses a huge challenge and must be removed by chemical or biological methods before the soil can be used. Another option is to adopt a hydroponic system, where plants grow in nutrient solutions without the need for "soil" or other loose materials.
Due to the natural environmental conditions on Mars — low temperature, low atmospheric pressure, and intense ultraviolet and cosmic radiation — plants cannot grow in the open air, so colonists need controlled greenhouse environments with adjustable temperature and humidity. If located on the Martian surface, such greenhouses can use natural sunlight; if built underground, they must rely on artificial lighting.
Apart from growing crops, energy supply is also one of the biggest challenges facing Mars colonies. The intensity of solar radiation on Mars is only 43% of that on Earth, which greatly limits the efficiency of solar power stations. In addition, intense sandstorms that last for weeks or even months will block solar panels, severely affecting energy output. While solar energy can be used as an auxiliary energy source, compact nuclear reactors are regarded as a solution to provide a stable and continuous energy supply. Reactors based on the technology developed by NASA in the Kilopower project can be transported to Mars via spacecraft such as Starship. Such reactors have high energy density and can operate normally in the harsh Martian environment independently of weather conditions or day and night cycles.
In the long run, if viable geothermal resources can be found on Mars, other technologies such as geothermal energy can also be considered. Apart from water resources and their potential agricultural application value, Mars has other advantages compared with other celestial bodies in the solar system: its day length is 24.6 hours, which is extremely close to the time on Earth, making it easier for humans to adapt. Mars' atmosphere, although very thin and dominated by carbon dioxide, can be used both for plant cultivation and converted into methane for fuel manufacturing via the Sabatier reaction. As mentioned earlier, this is the main reason why Elon Musk decided to use methane as fuel for Starship.
Since there is no oxygen and extremely low atmospheric pressure on Mars, habitats must be completely sealed to maintain an Earth-like environment, and at the same time must be able to resist cosmic radiation. Therefore, the initial settlements will most likely build sleeping areas underground, possibly covered with large domes to let sunlight in and illuminate areas suitable for outdoor activities. The cosmic ray dose rate on Mars is roughly the same as that on the International Space Station, and as long as the time for ground activities is limited to a small part of the day, the radiation dose can be controlled within a safe range.
Similar to the Moon, there are most likely huge lava tubes on Mars — tubular underground cavities formed by solidified lava. Such structures are formed during volcanic eruptions: when the outer layer of lava cools and solidifies while the inner layer continues to flow, a hollow space is left. Mars is home to many large volcanoes (for example, Olympus Mons, the largest dormant volcano in the solar system), and there is evidence of a large number of ancient lava flows. Including satellite images from the Mars Reconnaissance Orbiter, structures called "skylights" have been discovered, and these openings are most likely passages leading to underground lava tubes. Some of these Martian lava tubes may become ideal places for future human settlement, providing residents with natural protection against radiation, micrometeorites, and extreme temperature changes.
Even today, some countries have large-scale standalone shopping malls, which allow people to imagine what cities on Mars might look like. For example, the Dubai Mall covers an area of more than 12 million square feet, with an aquarium, an ice rink, numerous restaurants and hotels, all located in an environment with 24-hour air conditioning control. Another example is the West Edmonton Mall in Canada, which is also a completely independent building. In addition to various shops, it is also equipped with complete leisure facilities such as a water park, hotels and ice rinks.
People often draw an analogy between life on Mars and life in shopping malls, which is also described in the book Terraforming Mars: "People who walk around, dine and entertain in air-conditioned shopping malls in cities in extremely hot or cold countries do not live in a more natural environment than future Mars colonists living in pressurized residences... The feeling of living isolated from the outside world is actually very similar." However, building pressure-protected living facilities on other celestial bodies presents completely different technical challenges.
There have been many visions of how humans can survive on Mars. In Terraforming Mars, Chris Hayuk writes again: "The core concept of this Mars colony design is to extract water from the soil, and then use the pits excavated during the water extraction process to build apartments and buildings, with a 'public park' in the center of these buildings overlooking the Martian sky, while allowing natural sunlight to enter every apartment and building, avoiding residents' long-term direct exposure to radiation."
In relevant works, Robert Zubrin points out that establishing colonies and cities on Mars is completely feasible. But who will pay for it? He believes that the initial Mars missions may be funded by the state, while the long-term goal of establishing a colony on Mars requires innovation and investment from the private sector: "Even a Mars base with only a few hundred people may be able to survive on government grants, but a Martian society that could grow to a population of hundreds of thousands obviously cannot. To survive, a real Martian civilization must either become completely self-sufficient (which is almost impossible before the distant future), or be able to produce some kind of export product to pay for the required imported materials. The future of Mars depends on this issue, not only for human civilization on Mars, but also for the nature of the planet itself. If a sustainable Martian civilization can be established, its population size and ability to transform the planet will continue to grow. Mars was once a planet with a mild climate, and with enough effort, it can return to that state again." The advantages for people settling on a terraformed Mars are extremely obvious — in short, as long as a colony is established on Mars, terraforming will inevitably be implemented.
Zubrin emphasizes that Mars colonies will have unique advantages — it is more convenient and lower cost to travel from Mars to the resource-rich asteroid belt between Mars and Jupiter: "A 'triangular trade' model will be formed: the Earth provides high-tech manufactured products to Mars, Mars supplies low-tech manufactured goods and food to the asteroid belt and even the Moon, and those asteroids transport metals (and perhaps the Moon will supply helium-3) back to Earth."
Zubrin believes that the harsh living environment on Mars and the constant need to find new solutions will make Mars colonies a powerful innovation engine. Such innovations can form exportable intellectual property, which will eventually bring huge benefits to the Earth. "In short, Martian civilization is bound to be practical, because the situation forces it — just like American civilization in the 19th century. This forced pragmatism will give Mars a huge competitive advantage over those less pressured and therefore more tradition-bound societies on Earth. If necessity is the mother of invention, then Mars is the cradle that nurtures innovation."
Zubrin firmly believes that colonists have excellent creativity, and that they can build a prosperous economy and society on Mars, just like those early European immigrants who laid the foundation for the United States to later become the most successful country in history.
Despite all the above views, there are still many skeptics who believe that establishing a colony on Mars is not economically feasible. Matthew Winchell and Brendan Rosso point out: "Any economic return is extremely uncertain, because even if Mars can really export products, the transportation cost will be staggering; and at least in the initial stage, the demand of wealthy Earth people who are willing to go to Mars to live is likely to be very limited."
From the current perspective, this is indeed the case. However, if the cost of space travel continues to drop significantly as it has over the past decade, travel to Mars will no longer be affordable only by a very small number of wealthy people. Perhaps one day its cost will drop to a level comparable to that of emigrating from Europe to the United States in the past, and even those who sell their houses on Earth can use the proceeds to pay for the trip. Elon Musk and Zubrin estimate that the cost of a Mars trip could be as low as $200,000 or $300,000, a figure far lower than the average housing price in the United States.
As for export products, we should not only consider heavy industrial goods. Zubrin's vision mainly focuses on patents, because the harsh and unfamiliar environment on Mars will inevitably drive innovation, especially in fields such as food production, nuclear fission and fusion, geothermal energy, robotics, and artificial intelligence: "In my opinion, the earliest large-scale source of cash income that Mars colonists can obtain will be the sale and licensing of intellectual property. This actually stems from the characteristics of Martians themselves and their environment — they will be in a frontier environment that constantly challenges and even forces them to innovate, and will face a severe labor shortage, which will prompt them to innovate in labor-saving machinery, automation technology, robotics, and artificial intelligence. Since they can only rely on greenhouse agriculture, they will also face shortages of land and livestock, and then have to innovate in the field of biotechnology to cultivate high-yield and nutrient-rich crops. Due to the lack of high-quality fossil fuels, wind energy, hydropower or solar energy resources, they will have to seek innovation in the field of nuclear energy, including advanced nuclear fission technology designs... and nuclear fusion technology, because the content of deuterium on Mars, which is used as fuel for fusion reactors, is five times that of Earth. All these innovations will have great application value on Earth. Therefore, Martians will apply for patents for them and license the Earth to use these patents, and the resulting intellectual property sales revenue could be extremely considerable."
I think Zubrin is right, Martian cities will be very different from cities on Earth. First of all, robots will undertake all tasks within their capacity. Unlike humans, they will not be seriously affected by the pressure, lack of oxygen or radiation in the harsh Martian environment, and can work 24 hours a day without eating, resting or taking vacations. That is why in my science fiction novel 2075, the number of robots in those Martian settlements far exceeds that of humans.
There is also potential for profitable real estate transactions on Mars. I will discuss the issue of property ownership in detail in Chapter 10. However, assuming that private property exists on Mars, otherwise colonization cannot be realized, then the land market will soon prosper, attracting investors from Earth to speculate on the value of Martian land, expecting to resell it at a higher price in the future, especially plots near potential water sources. Mars is also attractive to the advertising and entertainment industries: its gravity is only 38% of that of Earth, which makes it possible to hold new types of sports events on Mars.
Some writers believe that Mars will attract many tourists, including mountaineers who are eager to climb Olympus Mons — a mountain about 2.5 times the height of Mount Everest (it is so wide that it can even stretch from New York City to Montreal, Canada across North America). Physicist Michio Kaku writes enthusiastically in his book The Future of Humanity: "Walking on the surface of Mars is undoubtedly the dream of every hiker."
Indeed, judging from the stunning images of Mars transmitted back by probes, this scenario is not difficult to imagine. But I don't think large-scale Mars tourism is likely to be realized, because not only does it take 6 to 9 months to travel to Mars, but there is a launch window only every 26 months. Tourists have to invest several years for such a trip, and only a few wealthy retirees can afford it. In contrast, tourists are more likely to choose to travel to the Moon, where a three-week trip is sufficient.
Society on Mars must also adopt a different organizational form from that on Earth, first of all, more rationalized. Martian society will inevitably tend towards a minimalist state model, similar to the early United States, because it is unsustainable to support non-productive people at the expense of productive people.
The long-term vision conceived by Zubrin, Elon Musk and other visionaries is to "terraform" Mars. This term was first proposed by Olaf Stapledon in his 1930 novel Last and First Men, where he described how humans could transform Venus when the Earth was no longer habitable. Later, science fiction writer Jack Williamson used the word in his 1942 short story Collision Orbit, making it more widely known, and it was eventually adopted by the entire scientific community.
Terraforming refers to the use of technical means to transform an uninhabitable planet into a habitable environment over several centuries. The proposed technologies include gradually heating the Martian atmosphere to create an artificial greenhouse effect, allowing liquid water to flow on Mars again 3 billion years later. Physicist Michio Kaku writes: "To start the terraforming process, we may inject methane and water vapor into the atmosphere to create an artificial greenhouse effect. These greenhouse gases can capture sunlight and continuously raise the temperature of the ice caps, and when the ice caps melt, they will release trapped water vapor and carbon dioxide." Zubrin and NASA scientist Christopher McKay propose to use fluorocarbon gases, because their greenhouse effect is stronger than that of methane, and unlike methane, they will not be destroyed by solar ultraviolet rays.
Another idea is to have satellites equipped with huge mirrors or solar panels orbiting Mars, and these mirrors or panels can be miles wide. Sunlight can be focused and shone onto the Martian ice caps, or energy can be converted by solar panels and then transmitted down in the form of microwaves.
There are even more radical ideas, such as "changing the orbits of small asteroids or comets to make them fall to Mars... the kinetic energy carried by these celestial bodies will be completely converted into heat, causing local warming around the impact point, and then releasing the substances that make them up". Giancarlo Genta admits that this sounds crazy, "but it actually imitates the natural mechanism of planet formation. It is believed that during the formation of the Earth, it obtained water and carbon (the latter may have formed organic compounds) from the falling comet nuclei."
This idea is full of fun, but also extremely risky, because by then humans will have already settled on Mars, and the entire process must be strictly controlled to avoid posing a threat to them.
In August 2024, a team of scientists led by Professor Edwin Kite of the University of Chicago proposed a completely new solution that is expected to achieve this goal in a more environmentally friendly way. They suggest using nanoparticles to heat Mars: "One third of the Martian surface is buried with shallow ice water, but the current temperature is too low for life to exist. Warming Mars with greenhouse gases requires a large amount of substances that are extremely scarce on the Martian surface. However, our research shows that using artificial aerosols made of materials easily available on Mars — such as conductive nanorods about 9 microns in length — the heating effect can be more than 5000 times better than the most ideal greenhouse gas. Such nanoparticles