Context
Long term survival of humanity
Stephen Hawking said that humans better start colonizing other planets to survive. He has a good point. Humans, and every species on Earth, are vulnerable to internal and external extinction risks. We can nuke ourselves or kill each other, are causing a mass extinction, are messing with the biosphere, may succumb to a more lethal pandemic, and so on. Note that these are just self-inflicted possiblities, there’s a slew of external factors that we have very little control over. The sun could start flaring, a supervolcano can erupt, a massive asteroid like the one that killed the dinosaurs might strike, a gamma ray burst may hit Earth, and so on.
The survival of humanity can be thought of as the data on a hard drive. All hard drives eventually fail; some fail within a month, others can last up to 10 years. But eventually all of them will fail and the data in them will also perish. This is why it’s important to have backups. Right now, humanity doesn’t have any backup; everything is on one hard drive (Earth). If something bad happens here, then we’re finished.
This doomsday scenario is always lurking with a low probability. The chances of these events seem very unlikely on human lifetime scales, but they do build up over thousands and millions of years. In about 300 million years, if there are any intelligent descendents still on Earth, they’ll want to leave soon because there isn’t much time until the Earth becomes uninhabitable even without a sudden doomsday event.
Where to look
The backup solution comes in a few forms. If we were a very advanced civilization, we would try to colonize other star systems or perhaps the whole galaxy. However, this scale of colonization is so far out of reach that we might want to come back to it at least a few centuries later. Trying to reach the closest star (~4 light years) with the fastest interstellar spacecraft we have, Voyager 1, will take around 20 000 years. Don’t even imagine attempting a galactic colonization with the 100 000 light year diameter of the Milky Way.
The most feasible backup solution for now is to go to Mars, for many reasons. First, it’s very close to Earth. Mars is a mere 50 million km away at its closest to Earth, and 400 million at its furthest. Most spacecraft took about 6 months to a year to reach Mars, so transporting people there isn’t impossible. An Earth-Mars communication is relatively easy too, light takes just 22 minutes complete a one-way trip at most. Compare that to the 17 hour one-way trip it takes to communicate with Voyager 1.
Besides making a trip easier, the proximity to Mars allowed us to study it. We mapped its surface, know what the atmosphere and composition is like, know there is ice locked up at the poles, and are confident that oceans existed there billions of years ago. The planet was likely very similar to Earth early on, and the materials needed for life are mostly present.
In short, Mars is the best target for colonization in the near run because of its proximity and similarities to Earth. This is why optimists think a human Martian colony could be established within just a decade or two. But is this really so easy? Just get a few people to Mars and they’ll manage?
Getting to Mars
Before even talking about the conditions on Mars, it’s important to mention just how far away the planet is in terms of human distances. Mars is less than a footstep away in cosmic scales, but even a million kilometers is an incredibly long distance for small things like us.
Like stated earlier, it takes spacecraft at least half a year to reach Mars. There’s several differences between transporting a machine and a person to great distances.
-
A machine can stay dormant for as long as it needs to. People cannot
This is the largest problem to address. A ‘measly’ 14 hour flight is hard enough to endure for many people, how would someone fare with a one year trip? Someone travelling to Mars needs to have all supplies onboard and efficiently reuse materials like on the ISS. There’s no restocking or getting off, the journey will be done in complete isolation.
Imagine transporting a group of people to Mars. If they dislike each other or tend to argue like bad roommates, how would they feel about being stuck with each other for at least half a year? A spacecraft is small, there would hardly be space to wander around.
The journey exposes travellers to solar radiation and micro-gravity for months. ISS astronauts are essentially the healthiest people you can find and train hard. They have to exercise every day to prevent bone and muscle decay, and even with that they become so weakened that they cannot stand up when arriving on Earth. This can technically be fixed by inducing artifical gravity with a spinning, cylindrical spaceship, or constantly accelerating at 1G, but the second option is impossible.
The radiation is a whole different problem. The easiest way to solve it is to have thick walls, but that makes the spacecraft heavy and worsens fuel requirements. The sun’s radiation is not good to bask in unfiltered, people already get sunburns in a few hours within Earth’s thick atmosphere and ozone layer.
A solution to many of these problems could be cryosleep like depicted in media. However, I want to say that it’s more likely we’ll figure out how to commercialize Martian voyages before figuring out cryosleep, if ever.
-
A person is more delicate than a rover
Landing a person on Mars is very different from landing a rover. The latter can get away with a parachute causing sudden decceleration in the atmosphere and soft-crash land using cushions, but people would get severely injured or die in this type of maneuver.
Not to mention that if someone from Mars wanted to head back to Earth, reusable rockets would likely be mandatory. We’re still trying to figure this on Earth, so figuring out how to maneuver rockets on a planet no one has been to is a great challenge. If we don’t figure this out, the first generation of people to land on Mars may have to stay there forever.
-
The trip is dangerous and small errors will lead to death
If something goes wrong, the crew will have to fix problems themselves. If problems are serious and cannot be fixed, the crew is likely doomed. A journey to Mars is like the odysseys done by sailors travelling to new continents in sailboats; except this time, the boat is sailing on lava and the ocean is about 50 000 times wider.
A few example risks that come to mind are micro-meteoroid impacts and electronic failure. Impacts by tiny debris happen very often in Earth orbiting objects, and these tiny pieces can punch through several centimeteres of metal. While the density of small debris may be much lower than in Earth orbit, the recently launched James Webb Space Telescope has already encountered micro-meteorides that inflicted damage.
Additionally, contact with Earth will take minutes to occur. Even at puny interplanetary distances, the speed of light no longer allows real-time communication. Crew members can no longer have a live conversation with someone on Earth, whether it’s a simple call to parents or for life-threatening emergency reporting. Everything must be performed in isolation from Earth.
This whole article could be about just the journey to Mars, but hopefully the idea is clear enough by now. Before even leaving Earth, we are hit with the incredibly risky and challenging journey of getting to Mars in the first place. Nothing financial has been mentioned here too. Sending anything to space is very expensive, trying this with ordinary people is not going to happen for a while.
Arrival
Let’s say we have the technology to transport people to Mars, and maybe even a round trip is possible. The first goal is to establish a base camp because no one can survive on the current Mars.
Temperatures drop below -100°C at night, there are dust storms that can engulf the whole surface, interstellar and harmful solar radiation is not blocked by the atmostphere, said atmosphere is virtually nonexistent and contains no oxygen, and there is no liquid water.
The crew would also have to get used to being pulled down by gravity again, especially the first few weeks when hardly anyone is able to stand. Mars’ surface gravity is about a third of the strength of Earth’s so perhaps adjusting will not take terribly long, but going from 0G to 0.3G is still a large difference.
Therefore, even establishing a base camp is going to be very difficult. Venturing outside without protective suits will lead to death, radiation will be a constant threat even indoors, food and other supplies will have to be carefully maintained, and so on.
Terraforming challenges
With the background and simplified arrival process out of the way, we can finally get into the challenges of the actual terraforming. While I am no expert of Mars or planetary engineering, these challenges are non-fictional.
First is the temporal aspect. The timescale needed to change significant objects like a planet will take centuries at least. Perhaps even a few millenia to even see slight results. This implies that the first few generations of people to go to Mars will likely always live under its current conditions; they are performing the ultimate sacrifice for future generations.
Atmosphere
Currently, the Martian atmosphere is about 1% as thick as Earth’s atmosphere. At this low pressure, the gasses cannot capture much heat and so the temperature plummets. Water evapourates away due to the low pressure and harmful radiation passes right through. Thickening the atmosphere is the biggest priority. It is only after this that temperature will rise, liquid water can exist, and oxygen can be maintained.
The easiest start would be to melt the polar ice caps on Mars. Because these contain carbon dioxide, melting them would help warm the planet. The ice caps also contain water ice, which would solve a Martian settler’s water problems. How we would melt such a large amount of ice is a complex question in and of itself.
One problem with puffing up the atmosphere is Mars’ weak gravity. The planet’s weak pull means that it cannot hold onto its atmosphere like the Earth does, and this is one of the two theorized reasons why the atmosphere is as thin as it is today. Over time (not on human lifetimes though), any gasses released into the atmosphere would gradually escape into space as solar winds gradually strip them away from the planet. Therefore, Mars as it is would need constant gas replenishments to maintain a thicker atmosphere.
Another problem is the source of the gas. Since Mars’ atmosphere is a hundred times thinner than Earth’s, you need a hundred times more gas to make it comfortable to go outside without protection. Where is that gas going to come from? The polar ice caps have a limited supply, and it’s not enough to thicken the air a hundred-fold. You can release some gas trapped in the surface, but that’s not enough either. The only way to get more gas is to bring it from somewhere else. And you can’t just ship gasses from Earth to Mars, that will take far too long. It can’t be any gas either, the Martian atmosphere would need a lot of greenhouse gasses; you can’t just lug some hydrogen from Jupiter (if we were even capable of doing that).
Lastly, maintaining Mars’ atmosphere even having solved the problems above would be challenging. Since the thicker atmosphere is warmer, the gasses are more energetic. This lowers the energy required for gasses to escape the atmosphere, so a warmer atmosphere would be significantly more leaky.
Magnetosphere
This is the second suspected reason for Mars’ atmosphere loss. Earth still has a molten core and is hot inside, which gives its magnetic field and geological activity. The duration of this activity depends on the planet’s mass. Mars being only a tenth of the Earth’s mass cooled much faster and lost its magnetic field, and seems to be geologically inactive.
The magnetosphere is responsible for deflecting most solar wind particles, which are good at chipping away planetary atmospheres. By losing its magnetosphere and weaker gravity, Mars’ atmosphere was doomed to be lost into space.
Is there a way to bring back the magnetosphere?
Yes, but not from within the planet. Trying that is equivalent to melting 1022 kg of rock and metal and getting it to churn. People already have difficulty imagining a billion dollars, how can you picture melting ten thousand billion billion kilograms of material?
There are some ideas where external devices can create a magnetic field that encompasses Mars, and this is perhaps one of the more feasible devices we’ll be able to create within a few decades. But even then, creating artificial magnetic fields and maintaining them is a great engineering challenge.
Gravity
Besides being not strong enough to hold a thick atmosphere, the weak gravity also has a more significant effect on anyone looking to go to Mars.
The human body, and all life on Earth, has evolved around a 1G gravitational field; our cells and biological functions all depend on Earth-strength gravity to function efficiently. Suddenly dropping that to 0.3G will cause some profound negative effects. If those effects hinder organisms on Mars from surviving, colonization will become a lot harder.
There’s no way to cheat with external devices like the magnetic field, gravity can’t be created out of nothing. The only way to make Mars’ gravitational field like Earth’s is to increase the planet’s mass. By 10 times. That’s on the magnitude of 1024 kg of rock and metal. In another explanation, imagine smashing Earth and Mars together. The resulting planet would only be 10% heavier than the current Earth.
One interesting consequence of the gravitational strength is the future divergence of life on Earth from Mars. If enough generations of creatures from Earth lived on Mars, they would evolve around the lower gravity. Hence, the anatomy of a future human descendent on Mars and Earth will likely be greatly different.
Ethics
The last point I want to mention in Mars colonization is a non-scientific question. A rule with spacecraft missions is to never let Earth’s life accidentally contaminate potentially inhabited worlds. For instance, the Cassini-Huygens mission to Saturn and its moons was destroyed at the end of the mission because some of Saturn’s moons could have life on them, and a probe crashing into one of those moons was unacceptable. So what if, some time before people head to Mars, we detect life there?
Asking this question is a little futile because humans have already sent many rovers to Mars. Sterilizing all organisms on anything is extremely difficult due to life’s persistence, so Mars may already be contaminated. But if Earth’s life hasn’t contaminated Martian life, what about it then? Do we have the right to trample on Martian life for our benefit? We have yet to find life anywhere else in the universe, so what do we do if we find another living world? Leave it alone? Indirectly contaminate it and perhaps snuff it out?
On Earth, invasive species don’t care and aren’t aware that they have contaminated some foreign environment. There’s nothing wrong with this, because technically we are an invasive species too. Following the same logic, we can say that colonizing Mars and potentially extinguishing native Martian life is inevitable, so we shouldn’t care. But as sentient beings, it’s interesting to discuss such ideas.
Conclusion
There’s a nearly infinite number of problems that a project like terraforming will encounter; even getting a person to Mars seems like a science-fiction story right now. This article hasn’t brought up how chemical cycles (water, carbon, etc.) will work, Martian climate pre and post-terraforming, how to deal with geological inactivity, the bioengineering required to grow food on Mars in the long run, how to mitigate dust storms that cover the surface, adjusting to the nearly doubled duration of a Martian year, and the list goes on.
Humans spread over the Earth by walking across different continents, inventing boats to carry them over oceans, and adjusting to harsh environments like mountains or deserts. The next step is to aim for the stars, but for now a stopgap solution is to head deeper into our solar system neighbourhood.
Whether it’s feasible or not, one day humans will want to migrate to other worlds in order to preserve themselves. Mars provides one of the best environments for the first settlement beyond Earth. The difficulty and timescales are on a scale we’ve never attempted, but it’s very likely that a serious try will be made within our lifetimes.
Quite amazing to think about, humans went from performing trans-oceanic flights to sending someone to the Moon, and are likely to try building homes on Mars. All within two centuries. Imagine what can happen within the next millenia. I want to see the power of upcoming engineering make this article into an outdated relic of early 21st century thinking. Maybe terraforming, and even travelling to other star systems, is possible; we were just born too early for it.