On to Mars

In a previous article I looked at the objectives of the next Moon mission, but as Elon Musk keeps urging, man’s future as a multi-planetary species depends not on going to the Moon but to Mars.

Beyond Mars are the gas giants, Jupiter and Saturn, and the frozen ice giants, Uranus and Neptune. It’s already clear that only their moons will be of potential interest to settlers. (Jupiter alone has over 90 moons.) But Mars has many advantages.

It’s a major lucky break that the Martian day is almost exactly the same length as an Earth day and that Mars has an axial tilt, giving it recognisable seasons. Mars also has 38% of Earth’s gravity. And it has huge amounts of water – if all its ice was melted, the entire planet would be covered in water over 35 metres deep. All of which makes Mars much more suitable for human habitation, although the Martian year lasts 687 Earth days, meaning that all its seasons are twice as long as ours.

Although Mars is only half Earth’s size it’s a world of extreme contrasts. Its southern hemisphere is ancient, heavily cratered highlands, its northern hemisphere low-lying plains. Its Tharsis Bulge, the size of North America, is 10 000 metres high while its highest (volcanic) mountain, Olympus Mons, is three times as high as Mt Everest. There is a vast network of canyons, some of them as deep as 7 000 metres. This network is as wide as the United States (US). These are the most extreme geological features in the whole solar system.

Using today’s chemical rockets, getting to Mars would take seven to nine months. Nuclear thermal propulsion could cut that time in half, greatly lowering the risks to the crew of zero gravity and radiation. A “launch window” from Earth occurs only every 26 months. Whichever method is chosen, there is the key drama of Mars Orbit Insertion, when the rocket would have to be slowed down at a very precise moment. Either an under- or an over-shoot would be fatal.

After this, the crew would face what is universally known as the Seven Minutes of Terror, something all the robotic explorers of Mars have already had to face. But experiencing the Seven Minutes with a rocket probably weighing tens or hundreds of tonnes will be something else again. It is by far the greatest technical challenge in the solar system.

Atmospheric Friction

A Mars rocket can’t just brake all the way down like the Apollo astronauts did on the airless moon because Mars has an atmosphere under 1% as dense as Earth’s. This means that atmospheric friction is sufficient to incinerate the rocket unless it has a strong heat shield.

On the other hand, the atmosphere is so weak that it doesn’t slow the rocket down the way that happens on Earth and that makes aids such as parachutes of little help. Instead, the retro-rockets would have to slow the craft down from over 20 000km/hour to land gently on Mars, with all systems working perfectly and precisely synchronised. That includes a parachute as big as a football field but strong enough to withstand supersonic speeds. When the parachute is cut away, the rocket would be in free fall, still at a great speed. It would then have to fire a “suicide burn” – a full-power rocket blast sufficient to slow the craft right down to zero – and land.

Going to Mars is quite different than all previous space travel. All such travel, the Apollo missions included, have been just cosmic camping, with all key supplies loaded on Earth and all waste stored for later disposal. But from the moment of take-off a Mars mission would have to be self-sufficient and everything would have to be recycled.

The first thing is to deploy a highly compressed inflatable habitat – much more spacious than the rocket’s cramped living quarters. Once inflated robot diggers will cover it with Martian regolith (soil) to a sufficient depth to blanket it off entirely from radiation. Solar arrays are quickly erected. Then comes MOXIE, previously tested by the Perseverance rover. The atmosphere is 95% CO2 and MOXIE breaks it into carbon and oxygen. MOXIE also makes liquid oxygen to power the return trip to Earth. Hydrogen is produced by electrolysing water and a by-product is methane, also excellent rocket fuel.

The regolith contains silicon, iron, aluminium, and titanium, as well as oxygen. All these elements can be extracted, used for building materials (with much use of 3D printers) or for breathing. But the regolith also contains toxic perchlorate salts and these have to be leached out. Even so, agriculture on Mars will have to be hydroponic – following extensive testing of such a system on the International Space Station – or even aeroponic. To go beyond that the leached regolith needs to be infused with organic matter – vegetable waste, treated human waste, food scrap, and so on. This will enable potatoes, sweet potatoes, soya beans, carrots, tomatoes, and green vegetables to be grown.

Energy

An even higher priority is energy. Because Mars only gets 43% of the Earth’s solar energy, solar panels will have to be more than twice as extensive and there will have to be a massive amount of battery storage to face the long freezing nights. However, the problem is that Martian dust will get everywhere and cling to surfaces, so the solar panels will need continuous cleaning.

But that won’t be enough to deal with the planet-encircling dust storms that occur every few years and last several weeks or even months. These can cut sunlight by 95%, a death sentence for a Mars colony unless it has back-up nuclear power.

As the Mars colony grows, the first Martian children will be born. Since babies can hardly do two-hour physical workouts, they will be born and raised under micro-gravity conditions, meaning they will have less muscle mass, smaller hearts and will thus probably be incapable of dealing with full Earth gravity. In other words, they will have to live out their lives on Mars or, possibly, on exploratory missions to the outer solar system. They will not be citizens of any Earth country and will be the first true Martians. They will grow taller and more slender than Earthlings and will be perfectly adapted to their environment, though of course it may take several generations for all the evolutionary changes to occur.

The future of the Martian economy lies in being a forward-operating base for the exploration and exploitation of opportunities in the outer solar system, starting with the fact that Mars will be the source of plentiful and cheap rocket fuel, so that rockets from Earth can refuel and resupply. Obviously, a primary focus will be mining both on Mars and in the asteroid belt, but the expansion of the colony will require a robust construction industry, using the plentiful local materials. Naturally, there will be a growing Martian tourism industry, but Mars will also need to be able to build its own rocket ships.

With all the required materials, much lower gravity, and plentiful fuel it should be much cheaper and easier to launch missions from Mars rather than from Earth. The energy required to lift any given weight into space from Mars is less than a quarter of the energy required on Earth.

Martian Governance

Inevitably, the Mars colony will become increasingly independent and will have to generate its own rules and governance. The key is that it will take 22 minutes for messages to travel between Earth and Mars, making real conversations, let alone remote control, impossible. The same remoteness was what led America to become independent of Britain, and the same dynamic will operate through space. So, Martians will inevitably end up taking many or even most of their own decisions. As the settlement expands, transport will be provided by a fleet of pressurised rovers, allowing the exploration of wide surrounding areas.

Inevitably, the most ambitious plans allow for terraforming – transforming Martian conditions into something more like Earth. The first two requirements – warming Mars up from its present frozen state and giving it a thicker atmosphere – are the two sides of one coin. The key would be the controlled release of Mars’s plentiful carbon dioxide to create a runaway greenhouse effect, with the CO2 heated by giant mirrors placed in space. This would melt some of Mars’s ice, creating lakes and probably a major sea. Mars would become a warm, wet, and cloudy world – with a toxic atmosphere.

At this point a variety of bacteria, lichens, cyanobacteria, and other hardy organisms from Earth would be introduced to the Martian lakes and sea. Over thousands of years these would absorb CO2 and release oxygen as a waste product. As oxygen levels rise, ferns, mosses, and grasses would be introduced, and finally bushes and trees. As they decay Mars would acquire its first real soil. However, Earth’s atmosphere is 21% oxygen and 78% nitrogen. Since Mars has very little nitrogen, to replicate that, vast quantities of nitrogen would have to be imported.

But that is not enough. Mars’s iron core solidified long ago, thus ending its magnetosphere. Without that the solar wind – a constant stream of charged particles – would eat into its atmosphere and carry it away into space. The only way to prevent that would be to give Mars its own magnetosphere. The suggestion is that a massive satellite with a powerful superconducting magnetic coil would be stationed at a Lagrange point 1.7 million kilometres away in the direction of the sun. The satellite would generate a vast magnetic field that would envelop the whole of Mars, and that in turn would deflect the solar wind around this artificial magnetosphere.

Ambitious

As may be seen, this process of terraforming is mightily ambitious and would take many thousands of years. But it would be possible, so the question is whether mankind would be willing to undertake such a huge and doubtless extremely costly process in order to create a second planet able to support human life. For Mars enthusiasts such as Musk, there is no question of the answer: the most precious thing in the universe is consciousness and thus far only mankind is known to possess it. So having a second human world provides an essential back-up should anything happen to the Earth: consciousness will be preserved.

This logic will not be accepted by all and the example of how space travel was left to one side after the first moon landings in 1969-72 – essentially because it was so costly – suggests that Earth’s financial imperatives will remain an important factor. On the other hand, it seems tolerably certain that the settlement of Mars will be part of a new space race between China and America.

This brings in all manner of other dynamics and complications that are impossible to calculate at this stage. For example, it seems clear that the Chinese will want to land their mission in the same area near the Martian south pole as the Americans. We don’t know how that will work out or what sort of modus vivendi they will arrive at.

What does seem certain is that the current competitive race to found a Moon settlement will lead on almost inevitably to missions to Mars as the only other planet in the solar system even remotely plausible for human settlement. Neither China nor the US – nor their respective allies – would be likely to accept that their rival great power should have monopoly control of Mars, so in that sense the race is already on.

RW Johnson