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The Mars Challenge

 Credit: NASA/KSC

Credit: NASA/KSC

By Jasmina Lazendic-Galloway & Tina Overton

Mars is the only other planet in the solar system where humans could possibly live, but the first colonists there will need some amazing science and meticulous planning to cope with cosmic radiation and find ways to generate air, water, food and energy.

Pale rays of sunlight bleed though the hazy rust-coloured sky. You survived the launch, the journey, descent and landing. All systems are go, so now it’s up to you to take the next step. You are the first person to travel to an alien planet, and humanity’s destiny depends on whether you can make it here and now.

Welcome to Mars, Earth’s red neighbour. If colonists can survive on this new frontier it will be the beginning of the human species’ future as a space-faring civilisation.

But things will not be easy for the first colonists on this lonely planet. How are you going to survive and achieve what you must to make this happen? Do you have what it takes? This may sound like science fiction, but right now various international and independent space agencies are working on manned missions to Mars.

Why go to Mars in the first place? Because it’s the only other planet humans can live on. Mercury is too hot because it’s closest to the Sun. Venus is too hot because it has built up too much greenhouse gases in its atmosphere, which trapped the heat and made Venus even hotter than Mercury – more than 400°C. So the only terrestrial planet left other than Earth is Mars.

So what are the difficulties that the first colonists will face? Some of them are familiar to us, and some of them will be completely new.

We’ll have a small group of people living in a hostile environment, cooped up in a small habitat, cut off for months from the rest of the humanity. This situation is somewhat similar to other extreme environments – think of crews in submarines, the South Pole research station or the International Space Station. Researchers have been examining the challenges of living in such settings, and how any negative effects on humans can be mitigated.

The main task people living on Mars will have to consider is creating basic resources like water. The surface of Mars is dry, but we have learned from many missions sent there already that there is plenty of water in the ground (or regolith). But since Mars is about –60°C on average, this water is mostly frozen. Like Earth, Mars also has two polar caps.

Mars and Earth would have had similar beginnings, with many planetesimals colliding to form a planet containing rocky material and metals. The heat produced from these collisions melts all the rocks, and different elements start to separate: lighter elements like silicon move to the top, and heavier elements like iron sink to the core of the new planet. The planet will start to cool, but some internal heat will remain due to radioactive elements that were present in the planetesimals. While the core of the planet is hot, it will keep iron in a molten state, and this will generate a magnetic field as the planet rotates. As the planet cools down further, the core will solidify and the magnetic field will disappear.

Mars is one-third the size of Earth, and about 3.5 billion years ago it used to have a thick atmosphere rich in CO2, and surface liquid water just like Earth. Since Mars is smaller, its core started solidifying sooner and its magnetic field almost disappeared, while Earth still has a strong magnetic field.

The Sun produces strong stellar winds made up of charged particles that interact with any medium. But if charged particles intercept a magnetic field, they are attracted onto the magnetic field lines. For instance, the solar wind that reaches Earth flows along the magnetic field lines, creating beautiful auroras where charged particles interact with our atmosphere at the magnetic poles .

On Mars, as the magnetic field was disappearing, the solar wind interacted with the whole atmosphere, dissociating CO2 molecules. Lighter elements like oxygen floated off into space, and the Martian atmosphere slowly became thinner. As the surface pressure fell, the temperatures also fell as there was less atmosphere to capture heat from the Sun. Surface water also started to evaporate, and some of it froze at the poles.

So this gives us the state of Mars today. Some of the necessary resources are present, but we need to have a manageable way to extract them. Humans need water, oxygen and food for basic survival.

One easy way to extract water would be to land near the polar caps and just melt the ice, but landing on the poles requires difficult manoeuvring and extra fuel. Landing anywhere else would then require extracting water from regolith. We could dig some regolith, place it in an oven, heat it up and separate the water from regolith as steam. Then we could collect the steam, cool it and we have water. This is not hard, but it requires a lot of energy, and this is another challenge on Mars.

The Martian atmosphere is only 1% of Earth’s, but it still has winds due to temperature differences between different atmospheric layers. The surface of Mars is covered in fine dust created from weathered rocks over a long period of time. This dust is carried easily by the wind, and sticks to solar panels, so the colonists cannot rely on solar power alone.

They will therefore have to bring with them something like Radioisotope Thermoelectric Generator units, which power space missions at the moment. These generators have a small amount of a radioactive element like plutonium-238, whose nuclei spontaneously break into two smaller nuclei and release energy in that process. These units can provide energy for a long periods of time for a small crew, but are not yet efficient enough to power a whole colony. Those first colonists will have the important job of finding potential geothermal power sources, or create some other kind of fuel.

Once we have water and power, creating oxygen is easy as we can pass an electrical current through water to separate oxygen and hydrogen. Hydrogen will come in handy to make fuel like methane, as carbon dioxide from the atmosphere can be combined with hydrogen to form methane and more water.

However, this electrolysis of water will also require energy. To minimise waste and save energy, both oxygen and water will have to be recycled in the habitat, as it is now done on the International Space Station.

Then there is food. We know that Martian regolith is very similar to the basalt-rich rocks created by Hawaii’s volcanoes. This material provides a good basis for growing plants in general, but Martian regolith lacks the organic matter needed to call it a soil. We can bring some soil-beneficial bacterial with us, but Martian regolith also contains some heavy elements that might get absorbed by plants and pass into humans.

So until we get to Mars and do some experiments, we will have to rely on hydroponics to grow our food. The plants will need water and light, so there are even more requirements for power.

While plants are good for us, they don’t provide enough energy to power hard-working colonists. Adding easily grown protein-rich food like algae and insects to our diets will be necessary.

The first colonists will also need to live underground. The lack of a magnetic field on Mars also means that cosmic rays, which are charged particles with even more energy than the solar wind, bombard the surface of the planet. These charged particles interact with matter: the more energy they have, the more interactions they have – like X-rays but stronger. The human body needs protection from such radiation, and the easiest way to create shelter on Mars is to go underground, or 3D-print a habitat from Martian regolith.

So the first colonists will have lots of digging and exploring to do. In that process it will be important to search for possible life on Mars. We know that Mars was suitable for microbial life to flourish in the past, and it’s possible that some of that microbial life survived in today’s extreme Martian conditions underground. Thus it will be important that colonists don’t contaminate Mars with our own microbes. An environmentally friendly habitat and exploration procedures will be a must.

While all this might seem too hard, that is not a reason not to do it. We know that more than 1700 near-Earth asteroids pose a potential threat to us. At the moment we don’t have any way to deflect an asteroid on a collision course with Earth, but having a second planet that humans can call home gives us a better chance of survival. Proactive people like Elon Musk are willing to invest their money to ensure such survival by building rockets that will enable humans to get to Mars. Ultimately, big challenges drive us to develop innovative solutions, which often find applications in our daily lives. So Mars is the next big challenge, and we should be getting ready for it.

Jasmina Lazendic-Galloway is a Lecturer in the School of Physics and Astronomy at Monash University. Tina Overton is Professor of Chemistry Education at Monash University.