Every human being is on Earth or, in a small number of cases, in orbit just above it. That may not be true in the future. In the coming years, people could return to the Moon and continue on to explore new frontiers like Mars. NASA sees Mars as a goal for the 2030s, but SpaceX is keen to send rockets directly to the red planet, and Elon Musk has frequently mused about forming a colony. Visiting Mars is one thing, but can we colonize it? Some technological and biological questions are outstanding, but this bit of science fiction might be realized in our lifetimes. Let's explore the current state of science and figure out if we can colonize Mars.
Getting to Mars
If you want to colonize Mars, you must get there, which means you need a big rocket. Space agencies have been sending small probes and landers to Mars for decades. While Mars is the planet next door, getting there takes a lot of power. For example, the Perseverance rover has a total mass of about 2,200 pounds (1,025 kilograms), and launching it took a 1.3 million-pound Atlas V rocket. That was followed by months of travel with a much smaller cruising stage. Robots don't need food, water, or protection from the environment, so any effort to get humans to Mars would require launching vastly more mass, which means we need big honking rockets.
Few rockets even in the testing stage could support crewed missions to Mars. NASA's Space Launch System (SLS) is capable of reaching the outer solar system—it was initially slated to handle the Europa Clipper mission, but that was handed off to SpaceX due to delays. Indeed, SLS development has been extremely slow. The enhanced versions that could be used for Mars launches are still years away, and SLS is disposable. That means a long lead time, as NASA has to build a rocket with a specific mission in mind. NASA has said it hopes to launch a crewed mission to Mars in the 2030s, but no one would be staying long-term. Supplying a Martian colony with disposable SLS-style rockets would be expensive.
SpaceX has two vehicles that are theoretically capable of reaching Mars. There's the Falcon Heavy, which is currently flying and has proven it can launch a 13,000-pound car beyond the orbit of Mars. This rocket is also going to launch the aforementioned Europa mission. However, SpaceX CEO Elon Musk has presented Starship as the Mars rocket since the earliest teasers. This rocket, however, is not yet fully operational.
Starship is the largest and most powerful rocket in the world, and it's being designed for full reusability like the Falcon 9. We're currently awaiting Starship's fourth orbital launch attempt. The first two ended in catastrophic failures, and the third was mostly successful until it attempted to reenter Earth's atmosphere. Musk has made a lot of big promises, but the strength of the Falcon 9 suggests SpaceX could pull this off.
For all his machinations and overpromising, Musk is the wealthiest person on Earth. His actual net worth varies based on the ebb and flow of markets, but even if Tesla tanked tomorrow, he'd still be obscenely rich with a fleet of privately owned rockets at his disposal. When a guy like Elon Musk says he's going to Mars multiple times over a period of years, you accept that he might actually do it. More likely, though, he'd send other people to Mars first to see how it goes. We've passed Musk's earliest predictions for a Mars mission, but he's now suggesting we could be just years away from a crewed landing.
Within a decade, there is a strong likelihood that we will have multiple vehicles capable of carrying people and materials to Mars. So, we can check this one off.
Living on Mars
So, we've gotten to Mars. Perhaps Starship exceeded expectations and regularly blasts colonists to the red planet, or maybe NASA or the CSA moved with uncharacteristic speed to establish the first outpost on Mars. Regardless of how we get there, we need to contend with the environment of an inhospitable surface. Mars has a thin atmosphere of carbon dioxide, endless expanses of dusty landscape, and about one-third of Earth's gravity. Can humans even live on Mars?
In a perfect universe, we would change Mars to be more like Earth. However, the technology necessary to terraform another planet is even more science-fiction than building a city on Mars. Elon Musk, again making outlandish proposals, once suggested we nuke the polar regions of Mars to thicken the atmosphere, but it's not just the atmosphere. Mars has no magnetic field, which means the atmosphere will be continuously stripped away by solar wind.
The lack of a magnetic field also means colonists would be exposed to intense radiation, up to 700 times more than they would encounter on Earth. Any human living on Mars must take extreme precautions to avoid radiation exposure. Habitats could be built underground or with shielding to lessen exposure, but any jaunt to the surface would be like getting a chest X-ray. Over years, the chance of radiation sickness and cancer becomes quite high.
Building a settlement that could protect residents from radiation will be a lot of work, and even SpaceX with a working Starship fleet might be hard-pressed to send all the necessary materials for construction. That's why NASA and others have been investigating in-situ resource utilization (ISRU) for the Moon and beyond. The agency has engaged with companies to build prototype habitats from simulated Martian and lunar regolith. NASA has made plans to ship a 3D printer to the Moon to test these construction techniques, but this won't happen for 5-10 years, based on the rate of Artemis launches.
Even with a properly shielded home, possibly made from Mars itself, you still have to contend with physics. Living on a planet with one-third of Earth's gravity might sound like fun, but there could be adverse side effects, and this is just a function of the planet's mass—there's no way to fix it. We talked to JPL's Adam Steltzner before the Perseverance landing, and he noted how little data we have on human physiology in low gravity. Your eyes may change shape, your muscles will atrophy, your spinal and lymphatic fluids might not flow correctly, and there could be novel pregnancy risks not seen on Earth. We don't even know if bones will grow and heal correctly without normal Earth gravity. If humans can't be happy, healthy, and fruitful on Mars, what's the point of going?
While we may soon have rockets capable of sending large groups of people and heavy payloads to Mars, the technology that would let those people safely live on Mars is much further out. We may not even be aware of some of the physiological issues we must solve.
The Martian Maybe
Back to Elon Musk, who, despite his penchant for exaggeration, could have the means to build a home for humans on Mars. Musk has famously presented ambitious timelines, claiming SpaceX could plant a colony on Mars in the 2020s. It's plausible that Starship will be a workhorse rocket later this decade, but shipping anyone off to Mars at that time would be ill-considered. Transportation is just the first step.
For all the talk about the fantastic adventure of colonizing another planet, few people would want to spend the remainder of their lives in a glorified tent in an arid, radioactive desert. The construction, manufacturing, and medical technology necessary for Mars colonization simply does not exist yet and may never exist. We might find that humans could never live safely or comfortably on a planet like Mars. Maybe.
We can't say anything more than "maybe" until our exploration of the red planet hits a new milestone: crewed missions. Once we have seen how humans fare on short Martian excursions, we can begin planning for long-term habitation. If we're lucky, crewed landings could happen in 10-15 years, but NASA's plans for the Moon are already slipping, and the Moon is a stepping stone to Mars. Still, we cannot rule out the possibility that the world's richest man will toss a few adventurers into a rocket somewhat sooner.
