What dangers must we overcome before we can live on Mars?
Can humans live on Mars? The answer is startlingly simple. Can humans live in Antarctica, where the temperatures regularly fall below -50ºC (-60ºF) and it’s dark for six months of the year? Can humans live below the ocean, where pressure rapidly increases with depth to crushing levels? Can humans live in space, where there’s no air at all?
As the limits of our ingenuity, our materials science and our chemistry have grown, we’ve gone from being able to tolerate only a narrow band of conditions to expanding our presence to almost every part of the globe, and now beyond it. Even the most hostile environment we’ve ever faced – the vacuum of space – has had a continuous human population for more than two decades.
So why not Mars? If we can live in Antarctica, if we can live in space, then surely it’s simply a question of logistics. If we can put enough materiel on the surface of the Red Planet, then perhaps we can survive – and even thrive – there.
But that ‘if’ is doing an awful lot of work. When we went to the Moon, the astronauts had to carry everything for their visit in their tiny, fragile landers. The Apollo missions spent between just one and three days on the surface – and it took only three days to get to the Moon itself. When a Mars-bound astronaut will spend months in space just getting to the landing spot, spending just a couple of days on the planet isn’t going to satisfy. Any mission, even the initial one, will necessarily be planned to be months-long, and that increases the complexity of the logistics enormously.
Mars is a particularly difficult planet to land on. It’s too far away from Earth to control any descent remotely – on average, a radio signal takes 12 minutes to cover the distance – so everything has to be preprogrammed in. A single error in either the computer or in its inputs will result in a new and expensive crater, of which there’ve been many. And once the command for landing has been given, there’s nothing that anyone back in Mission Control can do to intervene – the length of time it takes between that order, and a safe landing, is known as the ‘seven minutes of terror’.
The tenuous Martian atmosphere also complicates landing. It’s thick enough that any deorbiting spacecraft requires a heatshield to prevent it from burning up, but even the latest generation of vast, supersonic-rated parachutes struggles to provide significant purchase on the tenuous air on the way down. What remains of the orbit velocity has to be accounted for, or our landers will break against the frozen Martian surface.
A vast silver rocket with everything the astronauts need for their months-long stay simply isn’t practical
Various methods have been used, but the most consistently successful has been the ‘sky crane’, a disposable frame fitted with retro-rockets that burn until it’s hovering a few yards above the surface. It then winches the lander down gently, disengages its connecting cables, and then flies a safe distance away before its propellent runs out.
As expected, these calculations are very finely judged. Every pound of lander – the batteries, the solar panels, the scientific experiments – needs several kilogrammes of fuel in the sky crane. And every kilogramme of fuel in the sky crane requires several more kilogrammes of fuel on the rocket that takes it to Mars orbit. We’d send bigger, better landers to Mars if we could – but rocketry is at the very limits of our capabilities, getting a rover the size of a subcompact down to the ground. This has huge implications for conducting a successful crewed mission to Mars.
While we might dream of a vast silver rocket slowly descending to the dusty red surface, containing everything that the astronauts need for their months-long stay, we have to realise that it simply isn’t practical. That rocket, and the even-larger spaceship required to get it there, is beyond our projected launch capabilities for decades, if not centuries, to come. Planning for a successful Mars mission – for a permanent presence on Mars – requires us to work smarter, and use every advantage that we can. That includes those we can find on Mars itself.
Mars is a planet full of useful resources, and specific dangers. On the plus side, if we pick our landing site sensibly, we don’t need to take water. Water is heavy, and there’s nothing we can do to make it lighter. It takes up space, and there’s nothing we can do to make it smaller. And, even with the very best recycling facilities, the astronauts will still require a certain amount of spare water. Yet on Mars, there are many places where water, in the form of ice, is just part of the soil. Stick a shovel in the ground, and half of what gets picked up is water ice. And we can use that water for all sorts of things, not just drinking. We can use it for chemistry.
We can split it using electrolysis into its component gases. We can breathe the oxygen – which saves us from having to take tanked air. And if we recombine it with the hydrogen, we have an explosive mixture we might use as a rudimentary rocket fuel. If we go one stage further, we can scavenge the carbon from Mars’s carbon dioxide atmosphere and synthesise hydrocarbons for a better burn.
That carbon dioxide is also vital for plant growth. Add water, and a growing medium, and suddenly supplementing our freeze-dried packets of food becomes not just a possibility, but a mission goal. Humans consume a lot of calories, but we also eat with our eyes. A side salad isn’t just nutrition, but a morale booster.
Then there’s the stuff of Mars itself. We can use that as a construction material: make bricks from it, or simply heap it up and over our existing structures. And we really need to do that because life on the Martian surface isn’t straightforward.
The red dust has become a nanoparticle and is a major hazard, both to us and to our machines
Most immediately, there’s the temperature. Mars is an average of 80 million kilometres (50 million miles) further from the Sun, and its atmosphere is too thin to buffer the extremes of daily variations. Daytime temperatures in high summer can reach a balmy 21ºC (70ºF), but that same day, just before dawn, will have recorded -90ºC (-130ºF). Temperatures can fall as far as to freeze carbon dioxide out of the atmosphere. The extra insulation provided by several feet of Martian soil is going to be a welcome bonus.
Moreover, it’ll help with a long-term threat: radiation. The Sun spits out charged particles all the time, as well as high-energy light in the form of gamma and X-rays. On Earth, and to a lesser extent, on the Moon, we’re protected by Earth’s large magnetic field, which extends out into space and deflects the solar wind around us. Mars has no such magnetic field, and while conditions at the surface aren’t acutely life-threatening, every day that astronauts spend on the surface of Mars, they are accumulating radiation damage 10 to 20 times faster than they would on Earth – not counting the occasional solar flare that squeezes a decade’s worth of exposure into a single event.
Burying the astronauts’ base beneath the ground is one relatively easy solution to this radiation problem. So is building it inside a cave – volcanic areas of Mars are the sites of lava tubes that now form huge tunnels, with access through partial roof collapses.
The soil itself is toxic, rich with perchlorates. While these are a potential source of oxygen, perchlorates are water-soluble: contaminated soil cannot be used as a growing medium.
Then there is the dust. The red dust has been formed by hundreds of millions of years of continuous grinding of volcanic ash, becoming so fine that even the weak Martian winds can carry and keep it aloft for weeks at a time. The dust has become a nanoparticle – averaging 3μm (one 10,000th of an inch) – and is a major hazard, both to us and to our machines. It would be all but impossible to exclude the dust from living spaces: astronauts would carry it in from trips outside, even with assiduous measures – washing, hoovering, anti-static screens and air filtration – it would become part of the air they breathed and the food they ate. As well as the perchlorates previously mentioned, there’s other cancer-causing compounds, and the damage that fine-grained rock powder can cause specifically to lungs and eyes.
We’ve already lost one rover to the dust, which coated its solar panels. The more complex the machinery we take, the more certain we have to be of our seals and surfaces. Maintenance, together with the spare parts to back up that regime, would have to be strictly observed.
So how might we do this? We have parameters set by the number of crew we send, how long they plan to initially stay for, and what they intend to do when they get there. We have to plan to shelter, water and feed them, and then bring them home – and, if we’re intending anything other than a one-time visit, we need to keep our eye on the long game: what kind of infrastructure can we build that will be useful into the future?
Breaking down the problem into manageable bites is by far the most feasible way. What we learn from such incremental efforts – and what we have already learned – can be used to guide us as we work our way through the various elements that we need to execute a successful, and sustainable, Mars mission.
We must prioritise a safe landing without encumbering the descent with the weight of food, fuel, air and water
The first stage would be to increase our capabilities in low Earth orbit. A multi-month journey to Mars will require the largest spaceship we’ve ever built, and almost certainly something that can’t be lofted in a single launch. It’ll need to be constructed in space, using methods similar to the International Space Station. Fuel, together with everything needed to maintain life for the long journey, will need to be shipped from Earth – twice over, as it’ll be coming back. The descent craft will be a separate part of the ship, while the main portion stays in Mars orbit.
The second stage would be to send supplies ahead to the designated landing area. If we can, we should send robotic, self-erecting modules. This would ensure that there would be somewhere safe for the newly arrived astronauts to go, and enable us to prioritise a safe landing without encumbering the descent phase with the additional weight of food, fuel, air and water. And, this way, we wouldn’t have to commit astronauts to the long and arduous journey to Mars until we know there’s enough equipment in place to sustain them. If one rocket went astray – more than one is statistically likely to be lost – we’d simply send another.
One of the pieces of kit we’d send ahead would be an ascent module, an empty ship capable not just of landing on Mars, but also refuelling itself from the Martian atmosphere, ready for a return to the transfer ship in orbit.
To be clear, none of this is risk-free. Famously, an alternative speech was delivered in 1969 to the US president Richard Nixon in advance of Apollo 11’s landing, covering the scenario for failure. While our careful preparation has made success more likely, there are still situations that would be all but impossible to recover from. The main cause of this is how long it would take us to react to the unforeseen.
Supply chains are one of the most underestimated and misunderstood factors underpinning a modern economy. We are very used to being able to order anything, from anywhere, and it being available in a matter of days, if not hours. Manufacturers run just-in-time stocks from their suppliers, and retailers promise almost immediate delivery. Behind those storefronts lies a fantastically complex web of communications, transport, inventory control and personnel. We notice it only when it fails.
Almost everywhere on Earth is connected. Vital medicines, microchips, engine parts, even live organs for donation, are moved seamlessly between countries and continents. But there are places where this isn’t true, and they give us a first insight as to what challenges any Martian colonist might face.
Antarctica, despite our technology, remains one of the most isolated and inhospitable places on the planet. Almost everything that is needed – barring air, and water – has to be shipped or flown in, over vast distances and not without risk. Heavy seas, thick ice, a storm, an extra-cold snap: all see food and fuel stuck on a dock or on a runway. Antarctic bases don’t run a just-in-time supply chain, because when that supply chain is inevitably interrupted, people might die. Planning for those interruptions means having to take, and store, far more than is normally needed. Those of us who aren’t preppers will baulk at the amount of groceries required to keep a single person fed for a couple of months: the wintertime population of the Amundsen-Scott base, right on the South Pole, is 50.
Food, of course, can always be rationed. Heating can be reduced to one or two heavily insulated modules. There are back-up generators, and a doctor on site, and a modern, satellite-connected communications suite. Scientists are supported by a whole team of electricians, plumbers and technicians, working around the clock to maintain the infrastructure of the base, catching problems before they become critical and providing workaround solutions through their expertise.
The risk of death – by starvation, cold, asphyxiation, accident, illness, disease – has to be accepted
None of which has stopped problems occurring. Notably, if the base doctor falls ill and requires surgery, as has happened twice, the doctor ends up operating on themselves. In both cases, medical evacuation was impossible due to poor weather conditions and the distances involved. Some permanent bases still insist that personnel have their appendix removed before arrival.
Now, imagine that happening on Mars. A fully functioning base, sited in the most favourable position, and enjoying a multiply redundant infrastructure maintained by shifts of highly motivated and trained engineers, is still in a far, far more precarious position than any Antarctic base is today. A mercy dash to air-drop urgent medical supplies in Antarctica from the South Island of New Zealand is difficult but possible: the travel time, once everything is in place, is a matter of hours. Meanwhile, if the launch window is being kind, Earth to Mars is nine months. New generations of space drives will inevitably reduce that, but nothing can be done to erase the vast distances between the two planets. At best, 56 million kilometres (c35 million miles). At worst, when Earth is one side of the Sun, and Mars the other, 400 million kilometres (c250 million miles).
Without a doubt, it would be the longest supply chain in history, at the end of which is the harshest environment we have ever encountered. Even in the Age of Sail, the journey from England to Australia was faster.
If you’re the doctor on the first Mars mission, you have to decide not what drugs and bandages and surgical equipment you’re taking, but what you’re not taking. What can you do without? Both space and weight are limited. If you’re the engineer: how are you going to choose between this critical spare part and that critical spare part? Of course, you could ask the mission planners to send one – or two – of everything. But, given all that’s gone before, how feasible is that? At some point, enough will be too much. The risk of death – by starvation, by cold, by asphyxiation, by accident, by illness, by disease – has to be accepted.
As with all pioneers, the heaviest burden will fall on those who go first. They will be the most uncomfortable, the most precarious, the most vulnerable. Those who follow afterwards will have it, if not easy, certainly easier. The infrastructure of the initial base is designed to be expanded, as long as Earth holds faith with the project. For it’s certain that Mars will be utterly dependent on Earth for decades. How, though, would a Mars colony grow towards independence? Can we see that far ahead?
Manufacturing is a key technology here: not just the usual but vital supply of spare parts, but also the chemicals required for life. Specially tailored medicines, dietary supplements and plant nutrients will provide a measure of security for colonists; 3D printers with a vast library of models can start to deal with the physical, while the biological components can be conjured by automated synthesis machines.
Another cornerstone of a more independent Mars would be the colonists themselves – and specifically their education. Necessity is often the mother of invention, but Mars would be a very harsh taskmaster. A Martian colonist would need to devote a significant portion of their time to learning. The level of technology required to sustain a working colony would be high, and the number of personnel limited by available food and air. With everyone an expert in two or three separate areas of knowledge, a tragic accident to one need not turn into a crisis for all.
The highly precarious nature of life on Mars will inevitably lead to new social mores and codes of behaviour. Far from being rugged individualists, Martians will rely on each other for their very lives in a highly interdependent way – and they’ll reflect that, both in their relationships and their laws.
Just how divergent colonists become from the mother planet remains to be seen. But an independent Mars wouldn’t be a carbon-copy of any Earth society. It would be startlingly, and profoundly, alien.
The Red Planet: A Natural History of Mars (2022) by Simon Morden is published by Pegasus Books.